by Judith Curry
The skeptics thread has shown that it is plausible to be skeptical of a number of issues regarding the findings of IPCC WG1. However, whether atmospheric gases such as CO2 (and H20, CH4, and others) warm the planet is not an issue where skepticism is plausible.
Nevertheless, we have seen serious arguments (and even publications) against this theory:
The authors of these arguments believe that they should be convincing to other scientists. In that sense, these are serious arguments. While these arguments use physics, they are nevertheless erroneous. The G&T paper has been rebutted by Halpern (aka Eli Rabett), Colose et al., with a subsequent retort by G&T (both groups seem to be talking past each other). Are there any others? I am also unaware of rebuttals to Johnson?
The fact that such papers are being written by scientists who take themselves seriously and are being published implies to me that scientists have done a poor job of explaining and making the case for warming of the planet by gases such as CO2. Its easy to roll our eyes and mutter “cranks” when we see something crazy such as the sophistry in the little pamphlets put out by various anti-AGW advocacy groups. But these arguments refuting atmospheric warming by CO2 are being made by scientists that take themselves seriously on this issue.
So what have we been doing wrong in terms of explaining this, to other scientists, the technically savvy public, and the broader public? Our general argument consists of the following elements:
- a narrative with history, usually starting with Fourier, Tyndall, Arrhenius (see for example Weart, Wikipedia)
- the analogy to a greenhouse
- evidence for the existence of the planetary greenhouse effect (e.g. effective black body temperature, spectral IR measurements)
- the IPCC consensus
Well, #2 and #4 hinder rather than help. The greenhouse analogy has not served the scientific analogy very well, made painfully obvious by the G & T paper; John Nielsen-Gammon has a lucid new post on this, which looks like the start of an interesting series. The IPCC reports never actually explain the physics of the greenhouse gas mechanism. The explanations you find in popular books and undergraduate texts mainly address the issue from some combination of points #1, #2, #2.
There are graduate level texts on atmospheric radiative transfer, including:
- Goody and Yung
- Thomas and Stamnes
- Liou
- see here for Georgia Tech’s radiative transfer course, this is a really good site with .ppt lectures and lab (computational) modules.
Once you digest one of these books, you will have no trouble understanding how this works. However, these texts are pretty heavy going in terms of physics and maths.
There is a big gap between the simple explanations and the radiative transfer texts. The blogosphere has stepped in to fill the gap. Good explanations that I have come across are:
- scienceofdoom
- Real Climate
- Chris Colose
- Skeptical Science
- presumably there are others that I’ve missed?
However, a gap remains in terms of explaining the actual physical mechanisms. Yes, these sites give good explanations of the basic physics of radiative transfer and the Earth’s radiative energy balance, and provide empirical evidence for the existence of the greenhouse effect. But a good mechanistic explanation of the physical processes occurring seems absent, including an explanation of how local thermodynamic equilibrium is established in response to the absorption of infrared radiation by a small number of molecules. I don’t have a full understanding of what the actual issues are with the greenhouse effect skeptics (I suspect that Roy Spencer is painfully aware), but I have just received a copy of Slaying the Greenhouse Dragon, which I will read this weekend.
I don’t think the issue of not or mis- understanding the greenhouse effect is salient just for the public and a few seemingly confused scientists. I have to wonder how many scientists on the PNAS list that supports the consensus (including the biologists and economics) actually have a good understanding of the physical processes and have taken a graduate course in atmospheric radiative transfer.
We need to raise the level of our game in terms of explaining the planetary warming by infrared absorption of CO2 etc. The missing area of understanding seems to be the actual physical mechanism. Lets target an explanation at an audience that has taken 1 year each of undergraduate physics and chemistry, plus calculus. Once we have something that is convincing at this level, we can work on how to communicate this to the interested public (i.e. those that hang out in the climate blogosphere). Willis Eschenbach’s help is needed in translating this for the WUWT crowd.
Thoughts on how to approach this? An excellent start was made on this thread. See Chris Colose’s take here, which explains it in a way that I haven’t seen before.
Moderation note: this is a technical thread and comments will be moderated for relevance.
Judith,
I find many people in science have a hard time to grasp the concept of mechanics in motion on a molecular level. Compression and storage of energy is an extremely complex system as it can employ more than one energy or mechanical response.
A piece of plastic is flexible yet will shatter at a certain temperature below freezing as it carries molecules of water in the process of making the product.
Objects have a center of balance and the more complex objects then have an overall center of balance with all the different components inside having different densities having their own center of balances. These shift in motion, compressing and expanding. Flexible on a molecular level.
Gases, are effected by temperature, pressure and motional energy to change their densities and compress into a whole new form of liquid storing vast amounts of energy.
When physicists discuss the use and abuse of the Second Law of Thermodynamics as applied to climate science I listen closely. The G&T09 article (Falsification of the CO2 Greenhouse Effect), the Halpern (2010) rebuttal and the subsequent retort by G&T leave me “uncertain” as it appears that each author does not speak directly to each objection. Earlier Dr. Curry, you objected to a cartoon depiction of climate mechanics still available on a NASA web site as a way of dismissing an article that argued against CO2’s major role in a greenhouse effect. My experience with turbulence at the boundary of the air:water interface, and some familiarity with the limits of the Reynold’s Number to describe turbulent flow (uniform density for one), in part has me “not so sure” in accepting each author’s arguement wholely. I do not have a unified replacement climate hypothesis for the CO2 driver one in use today. I am intrigued by the moon’s tidal influence upon our atmospheric sea, the sun’s energy output spectrum, the photons that seem to rattle around in clouds, alien cosmic rays helping to make clouds, orbital excursions of planets and their gravitational pull on the sun as well as the limits (equilibrium condition assumptions) and boundaries (tail end of equations which are assumed to be small and therefore can be ignored) of the laws of physics including the conservation of energy. I remain in a “muddle” so I keep plodding through each arguement and sometimes, paywalls. Thank you for your patients. I may sit in the back of the classroom, yet I am still listening.
“I do not have a unified replacement climate hypothesis for the CO2 driver one in use today.”
RiH008, simplistic as my mind is – and perhaps hubristic at the same time – I’d suggest this, and I’d propose that each be taken and studied with an attempt to falsify it:
THE LAND USE WARMING MISDIAGNOSIS.
1. What warming there is is local, having to do with urban heat islands, and this because of land use changes as opposed to atmospheric chemistry. We know there is some UHI, so the questions become how much and does it affect the rest of the globe (i.e., the non-urban stations’ records).
2. It is local because many, many rural stations show no warming at all in the raw data. Global means widespread and more or less ubiquitous, therefore if the heat from urban heat islands is not affecting locations 50-100 miles away, then how truly global is it?
3. The apparent overall warming in some studies is due to incorrect adjustments at various points in the methodology, leaving artifacts of the processing to give the impression of warming when there is no intrinsic warming. True determination of warming can be accomplished by the inclusion of the many thousands of stations currently left out of the GHCN database, meaning that the coverage of the planet is more uniform.
4. The effect of station near-environments has not adequately been taken into account as to micro heat islands, and when that is factored in the warming at those stations will be less than it is currently be thought to be. What the amount is we cannot know now; I predict (along with many others) that this effect will substantially erase the apparent warming trend in the existing studies.
MANY skeptics do not doubt that we have done things that affect the readings on our thermometers. However, this group argues that CO2 is not the culprit, but land use due to population growth. How much that effect is, overall, has not yet been studied – in big part because the demonization of CO2 has swallowed up the vast majority of study grants. We argue that it will dwarf the CO2 effect.
The cure for this warming is threefold: To site met stations properly to correct the erroneous readings – in almost all cases toward the cool end of the spectrum. To also arrive at accurate site-specific UHI values and use them. And to reduce the population of the planet, especially in regards to centralizing population in urban areas.
When all is said and done, CO2 will be found to have been an insignificant player, and all the money saved by not slaying a dragon that was harming no one can be used to improve land use.
And finally, since those rural stations aren’t warming – meaning little to no heat is making its way to them before being dispersed up off the ground – we will find that even the land use changes will have only modest effects.
My hope is that Dr. Nielsen-Gammon will post on this here at more length.
http://blogs.chron.com/climateabyss/2010/11/the_tyndall_gas_effect_part_1.html
Dr. N-G has officially declared the greenhouse effect dead as a way to describe the behavior of gasses in the atmosphere.
Credit to the good Dr. for having the strength of commitment to take this position.
I like the name he has chosen, by the way.
Dr. Curry,
I should have finished my coffee prior to posting the above post. You clearly saw Dr. N-G’s post prior to my post. In my coffee deprived state, I skimmed right past your reference to it.
I still hope he will comment here on his clarification.
I would point out that the various terms using ‘greenhouse’ and now apparently being discarded were all brought to the public square by the climate science community.
If that family of terms are now agreed to be inaccurate, why is that a problem for the skeptical community?
If I understand this fully, I am gratified that the greenhouse effect is being laid aside, finally.
But lest we forget:
It is not just A greenhouse effect we are talking about, but a “Runaway Greenhouse Effect,” that one invented by Carl Sagan to explain the 800-900°F surface temperature on Venus (with its 96% carbon dioxide atmosphere) and then applied for well over a decade by people who claimed it also applied to the Earth (with its 0.03% carbon dioxide). Sagan invented it to spare astronomers the anguish of having Immanuel Velikovsky be right in his exactly correct prediction of that surface temp of Venus. It was, in fact, nothing more than a speculation, but it was seized upon by science – because they had no other aces up their sleeves. It would not do to let the infamous Velikovsky have the last word.
So, the speculation of Sagan about one planet was applied to a planet with a massively different atmosphere. All of the Nitrogen and all of the Oxygen (not to mention the Argon) in Earth’s atmosphere was conveniently overlooked.
In the haste to scare people into seeing CO2 as an imminent threat, we we the public were bombarded with images of melting glaciers and icecaps, and everything up to boiling oceans. And, the global warming community may or may not currently use what they now call merely “the greenhouse effect,” but we all remember it as “the runaway greenhouse effect.” The climate warming community still uses the greenhouse arguments when they talk about climate “sensitivity,” though without calling on the tainted term “greenhouse effect” so much anymore. “Sensitivity” as they use it still means “runaway,” whether they run from “greenhouse effect” or not.
It was a speculation, not a fact, when Sagan conjured it up out of the mists in the 1970s and it remains a speculation. In fact, no one knows why Venus’ surface temperature is so hot. There are hypotheses and little more. In the 1970s there weren’t even good hypotheses, only a guess. When it was used in the 1980s and 1990s as a foundation for the threatened (“runaway”) global warming, it was still a speculation. Being revisionists about the AGW history will not let the (runaway) global warming community soft-pedal their past; we can remember what they tried to sell the world on. And the biggest term was “greenhouse effect”, preceded by “runaway.”
I do recall a couple of years ago on WUWT when this greenhouse was discussed and it was agreed on that “greenhouse effect” was an unfortunate and incorrect choice of terms. Since then – amazingly, and maybe merely coincidentally – the AGW folks stopped using it, forsaking it for “re-radiation.”
I just wonder if we will hear of “runaway re-radiation ” sometimes soon. If so, they don’t have Sagan to be their Galahad. It would have been his kind of exaggeration. (No, I am not a Sagan fan. I thought he was the most boring, most posturing scientist on the face of the planet…)
“It was, in fact, nothing more than a speculation, but it was seized upon by science – because they had no other aces up their sleeves.” should have been:
“Sagan’s speculation was, in fact, nothing more than a speculation, but it was seized upon by science – because they had no other aces up their sleeves.”
feet2thefire, you say “If I understand this fully, I am gratified that the greenhouse effect is being laid aside, finally” but it has not been laid aside. The “greenhouse effect” is still a reality but the IPCC’s speculation about how significant any increase in atmospheric CO2 is seriously exaggerated. Roger Taguchi has provided excellent anayses here, particularly in his comments of Feb. 22, Feb. 7 & Feb. 9 (the last 3 major posts) which I recommend that you read carefully.
The IPCC’s claim that our continuing use of fossil fuels is leading to a “Runaway Greenhouse Effect” causing catastrophic changes in the different global climates (CACC) is nothing but politically motivated propaganda having nothing to do with trying to take over Nature’s job of controlling global climates. There is speculation that the UN’s real agenda include the redistribution of wealth from taxpayers in developed economies, some possibly to go to give aid to underdeveloped economies but the bulk to go towards:
– establishment of a framework for global government,
– enhancing the finances of a privileged few.
Such speculation may not be far from the truth. There are plenty of power-hungry individuals involved in this scam.
Best regards, Pete Ridley
It takes no ‘strength of commitment’ to say what everyone already knows, the ‘greenhouse’ effect is a poor choice of name or analogy. But analogies, by their nature, are usually deficient in many ways. An atom, as taught to me in early science classes, is like a ball. Well, it is, but that’s also a highly deficient analogy, but it still gives you an initial idea to hang your understanding on.
Good Morning,
I have seen no news announcements of a revolution in climate thinking, and a withdrawal of the IPCC-sponsored consensus, so it is clear that what anyone has written so far has not been accepted by the other side. I suggest that any hypothesized explanation on the molecular level should not be considered fundamental — Joe LaLonde’s post above sounds like Descartes on vortices in the ether, explaining everything and nothing. We physicists will always insist upon explanations that work on the direct observational level, like “heat rises”, or “you can’t get more out than you put in” (and pretending you can, if you only imagine two competing large flows, that mostly cancel each other, is intellectual fraud — you are deluding yourself, and anyone you insist upon “educating”).
I consider it proven that Venus’s heat is not due to the greenhouse effect as promulgated by the IPCC scientists, by direct comparison of the Earth and Venus atmospheres over corresponding pressure levels in each. I have done it here, and I afterwards read in Gerlich and Tscheuschner’s recent articles that they specifically recommend doing this.) Not only is Venus’ s atmosphere largely opaque to incoming light (visible freq. range), so the surface is cut out as a source of heat for the atmosphere, but the temperature at corresponding pressure levels of the two atmospheres is very closely in direct (fourth root) ratio with the incident solar power in the two cases. This directly indicates the two atmospheres are heated in the same way, and that must be: directly, by the IR portion of the Sun’s incident energy. Ah, this is why it gets colder as I drive up into the mountains, and why the snow stays, above a certain altitude — the surface is not warming the atmosphere, the atmosphere at altitude is cooling the surface. But don’t forget the ocean, as a heat sink/source, and El Nino et al, as boundary conditions. A pretty mystery to unravel, and you won’t unravel it by quantum mechanics or isolated examples of molecular interactions. Heat transfer is a bulk effect, and essentially, maddeningly diffuse, like water flowing through your fingers, or any sieve you try to hold it with — you can’t direct it, back to the surface for example. Heat does rise (except in a temperature inversion, localized and transient). You can’t trap or slow down IR radiation with air, or keep it from giving up its energy to the air, if it can, as soon as it can. It is just another path for the heat to take, not an obstacle to it. But I sit in an empty room; no one is listening — are they? And I am, thankfully or sadly, not a climate scientist, just an older, independent physicist. No doubt, I have overreached. You’re going to have to figure it out for yourselves, won’t you?
Sounds about right to me Harry.
Given that net LW cools the surface at sea level by ~70W/m^2 we should only be interested in the height in the atmosphere the radiation to space takes place at. The rise in Co2 has theoretically raised that by 1-1.5% or 100 to 150 meters.
Is this a big deal or small potatoes?
I’m sorry, an error in my link (I did it from memory, wrongly), it should be:
Venus: No Greenhouse Effect
Someone needs to tell Hansen and others, since he has been selling the idea of a runaway greenhouse effect ‘like Venus’ happening in on Earth if we do not do what he wants.
The more I think about this, I think the abandonment of the ‘greenhouse’ is not simply a rose by any other name. This was a major selling point of the AGW movement.
No, tallbloke, I can’t agree (though I wish everyone could), the very close Earth/Venus comparison tells me there is no measurable greenhouse effect at all on Venus, or on Earth (which has much less carbon dioxide in the air). At a lapse rate of -6.5K/km, the effect you mention would mean a temperature rise of nearly a full degree, easily measurable and thus wrong, based on what the clear Earth/Venus data tells me. The fundamental disagreement between climate scientists and physicists like myself is the trust the former put into simplistic radiation transfer arguments, which we see has led them into darkness. The simple way I look at it, the temperature lapse rate depends on the bulk specific heat of the atmosphere, and at 400 ppm, carbon dioxide cannot affect that. No doubt climate radiationists would insist that it can, somehow, through its IR absorption, but I would insist that it cannot, because that absorption (and emission) cannot hold back (as they believe it can) the relevant heat transfer demanded by the lapse rate. The bulk properties of the whole atmosphere cannot be affected by a negligible fraction of it — which is what a basic physical intuition would suggest even without hard data. I consider changes in the IR-absorbing constituents of the atmosphere rather as homeostatic controls against global temperature changes, a negative feedback against runaway temperatures, either up or down. As I see it, when the temperature goes up, the oceans release carbon dioxide, which provides an improved heat transfer upwards, and out to space, thus mitigating the temperature change. Rather than speculating on the degree to which the “greenhouse effect” can effect such a change, I think it’s a matter of how big is the homeostatic effect of added co2 (and water vapor) against the change. As a physicist, I suspect it is a large fraction of the unobstructed change itself. There is no equilibrium, of course, so this simple view is certainly not all there is to know.
“The bulk properties of the whole atmosphere cannot be affected by a negligible fraction of it — which is what a basic physical intuition would suggest even without hard data.”
A statement like the above is easy to disprove: Phase changes of water vapor has a tremendous impact on the properties of the atmosphere yet makes up only 1-4% of the total atmosphere (a negligible fraction). Another example where heuristic intuition leads to an incorrect conclusion.
Phase changes of water vapor are localized, and don’t change the lapse rate overall, otherwise we wouldn’t even be talking about a lapse rate as a general condition of the atmosphere. You haven’t disproved anything.
I agree, minute amounts can make a huge difference.
If I leave a bath full of water but with a tap dripping overnight, each drip might be a negligible fraction of the total in the bath but it will still overflow. I can make it an even smaller fraction by using a swimming pool as my example, the drip will still cause an overflow.
Seemingly minute changes in the concentration of CO2 in the atmosphere could have a similar effect.
Louise, your swimming pool example shows exactly the tiny local effect that Harry mentions, as evaporation from the pool surface would greatly exceed the amount of incoming water from the dripping tap. Now, if you are talking about an indoor swimming pool, that is another matter.
Isn’t the whole issue of sensitivity analogous to ‘we don’t know the rate of evaporation’ in this example.
We do know that we have a dripping tap and the drip is getting faster (ie we’re increasing the rate at which we (humanity)release CO2 into the atmosphere) but we don’t know if the evaporation will keep up with this increase.
And when it does overflow it will do so at exactly the same rate as your dripping tap (ignoring any effects due to evaporation). You will end up with a small puddle on the floor, just as if there was no swimming pool in the system at all.
I fail to see the point you are trying to make.
The analysis on your website has serious problems.
The pressure range of your analysis corresponds to an altitude of ca 45-60 km. The Venusian cloud tops that reflect 70% of the incident light are at an altitude of up to 60 km. The ratio of the albedos of Venus and Earth near cancel out the 1.91 incident radiation, so the net radiation is in fact about the same as on the earth, which demolishes your calculation and hence your conclusion.
So all you are doing is comparing the adiabatic lapse rates of the two planets and saying they are the same. Surprise surprise.
For me the Georgia Tech Link goes to the same destination as the pnas-Link.
fixed, thx see http://irina.eas.gatech.edu/irina/EAS8803_Fall2009/Default.aspx
The link to the publication by Gerlich and Tscheuschner does not seem to work.
others?
Miskolzci seems to be a glaring omission here.
http://miskolczi.webs.com/
thx, i’ve added it
Judith
In so stating the problem, you are close to denying the scientific method. Skepticism is ALWAYS possible. e.g. the issue of the magnitude of the effect vs “if it exists”. Correct modeling etc. Compensation by water vapor/precipitation/clouds etc.
Physicists continue to to test gravity, relativity etc as measurement capabilities increase.
Ferenc Miskolczi is one of a handful of world class experts who have mastered the Line by Line quantitative radiation transfer. See HARTCODE – it has 3000 line radiation models with ppm resolution calculations!
See Zagoni The Saturated Greenhouse Effect of Ferenc Miskolczi
He dig into Milne’s 1922 original greenhouse equations and discovered and fixed a major flaw in the boundary conditions – the assumption of infinite thickness. That corrected a major step change in temperature at the earth’s surface etc. See Zagoni p 41-45 etc.
He reviewed radiosonde data and discovered major errors in Kiehl & Trenberth’s 1997 etc See Zagoni p 68, 69
Using HARTCODE, he has discovered that the upward and downward radiation are almost exactly equal.
The major controversy is over his modeling up/down radiation up as about equal and the consequences for the 1D average.
The next step is to quantify the small differences that become significant primarily at the outer atmosphere.
He knows more about greenhouse gas radiation than 99% of your readers/posters. Take his results seriously for the insights they provide and see how to correct/build on them.
The greenhouse effect and its magnitude is one thing, debating over whether CO2 warms the planet through infrared emission and absorption is another; I don’t see any point to debating the latter.
Re: Miskolczi:
If you know a little calculus, you can find the mathematical internal inconsistency in the derivation of his ‘new solution’ to the Milne problem.
If you understand a little classical radiative transfer, you can discern the fallacy of his ‘new solution’, even without doing the math.
If you understand some basics about atmospheric structure (see Nullius in Verba, this thread) you can appreciate the irrelevance of his ‘new solution’ in any case.
If you know some basic physics, you can readily spot the phony energy conservation equation he invokes.
If you understand some aspects of atmospheric radiative transfer, you will see why the data M presents in support of his theory, really does nothing of the kind.
You can do this for yourself.
I recall enough high school calculus to know that a finite atmosphere boundary condition will give different results from an infinite atmosphere. Furthermore, Milne 1922
Perhaps you will honor us by providing the corrected solution for radiation absorption in a finite atmosphere compared to Milne’s 1922 infinite thickness assumption based on Eddington. Please detail the errors in Miskolczi’s 2007 derivation.
Then perhaps you could enlighten us as to the differences between conservation of energy, minimization of entropy, and maximization of entropy of climate.
David – The Milne problem admits only two boundary conditions, generally applied at TOA and taken to be that (1) the outward LW radiation be equal to the total flux generated within the atmosphere (in the case of stars) or the impinging SW radiation (in the case of a planetarty atmosphere), and (2) the inward LW radiation is zero (no LW radiation from space). Imposing a further arbitrary boundary condition at the base of the atmosphere, as M wishes to do, generally causes one of the TOA boundary conditions to be violated (number 2, above, in M’s case), which renders any such solution unphysical. This property reflects a limitation of the Milne problem and the approximations used to derive it. In many atmospheres, this limitation is resolved by the realization that strict radiative energy balance does not apply in the underlying convective region; one can readliy imagine other conditions under which the Milne formalism fails to be a good approximation. Thus, the application of a BOA boundary condition is neither necessary nor correct.
Furthermore, M’s derivation (in Appendix B) is internally inconsistent. To find a functional extremum in his integration constant Bo (as required by his ‘energy minimization’ hypothesis), he sets a derivative with respect to Tau_a (total optical depth) equal to zero, holding Bg constant (eqns B9, B10), and so derives a solution for Bg which explicitly depends on Tau_a, in self-contradiction. In fact, using the ‘solution’ for Bg (eqn B11) in his expression for Bo (eqn B7), one finds that there is no extremum in Bo.
M’s eqn 7 is the phony energy conservation equation; it has no physical basis.
(I should say that, upon first contemplating these apparent flaws, I contacted Dr. Miskolczi by email, to which he graciously replied. Unfortunately, his explanations made no more sense to me than his paper did.)
Further criticisms of Miskolczi’s work, of which you are probably aware, can be found at:
Roy Spencer
Nick Stokes
Paper by Rob van Dorland1 and Piers M. Forster (sorry, can’t find the link right now)
Also, comments by Arthur Smith on various threads, and Neal J. King on Miskolczi’s mysterious application of the virial theorem:
NJK on virial theorem
Finally, I see that my comment above has a condescending tone that I did not intend; for this I apologize. I simply wanted to say that many of the flaws in Miskolczi (2007) are readily apparent to anyone who takes the trouble to carefully examine the paper.
Thanks Pat.
Accepted. Apologies for responding in kind.
I will look at that those derivations more carefully.
Appreciate your clarification for the assumptions SW/LW division at Top of Atmosphere.
Doesn’t Miskolczi also change from an infinite to a finite atmosphere?
Re:
I don’t follow. Why don’t the planetary surface conditions matter? Radiation, conduction, convection at the surface should impact the temperature and SW/LW near the surface.
e.g. Miskolczi assumes 3) a black body interface
(SW Absorptivity/ LW emissivity = 1)
He also assumes
4) that the gas temperature at the surface and the surface temperature are equal.
How do 3) and 4) cause problems to your 2) of inward LW at TOA?
At the extreme, won’t a planetary surface A/E = Zero affect the solution. i.e., no SW surface absorption. Similarly with emissivity of 0.01 instead of 1, reducing LW radiation?
(I presume a quantitative generic case would combine 1+2 and use a line by line radiation model. e.g. assume the total outward radiation be equal to the total flux generated within the atmosphere (in the case of stars) or that impinging radiation (in the case of a planetary atmosphere), plus any planetary internal heat generation.
Radiation, gas composition & planetary mass all affect the atmospheric profile or lapse rate. For an almost complete thermodynamic solution to the atmospheric profile. See:
Prediction of the Standard Atmosphere Profiles of Temperature, Pressure, and Density with Height for the Lower Atmosphere by Solution of the (S−S) Integral Equations of Transfer and Evaluation of the Potential for Profile Perturbation by Combustion Emissions
Robert H. Essenhigh, Energy Fuels, 2006, 20 (3), 1057-1067 • DOI: 10.1021/ef050276y)
David — please see reply below (to avoid margin scrunching)
Pat Cassen
Thanks – see my response following your post below.
my response
See also my posts to A. Lacis at: Comment on “unphysical constraint”
DH response to A. Lacis comment on order of calculations
http://judithcurry.com/2010/12/02/best-of-the-greenhouse/#comment-18271
Pat thanks for the links. I have pulled them and am reading them.
Non-technical summary of G&T here:
http://www.tech-know.eu/uploads/Falsification_of_the_Atmospheric_CO2_Greenhouse_Effects.pdf
Judith,
If you would like to see a couple of write ups on the atmospheric greenhouse effect by a couple of skeptics, please read the following (and some of the comment discussions). Just because some skeptics don’t accept the valid physics (and many supporters of CAGW assume large feedback and tipping points that are not supported by anything real), don’t tend to lump them in one batch. I think many of the points made by G&T and others are valid but incomplete (although there may also be errors, but I don’t specifically know that). I think both sides are tending to talk past each other, and misunderstanding what the other claims.
http://climateclash.com/2010/11/25/g1-the-atmospheric-greenhouse-effect-and-its-effect-on-agw/
http://climateclash.com/2010/11/28/g2-greenhouse-gas-effect/
Thanks for pointing this out, i haven’t gone through this yet.
Judith Curry says:
whether atmospheric gases such as CO2 (and H20, CH4, and others) warm the planet is not an issue where skepticism is plausible
For Miskolczi, this is not the issue. The issue is whether additional ghg’s are going to warm the atmosphere and ground further.
And I’m still awaiting your explanation of how LW radiation can heat the oceans, as your bare assertion of the ‘fact’ doesn’t satisfy my need for falsifiable content.
tallbloke, i wrote a long response on the ocean heating, if you can find your original query, it should be there, it was a lengthy discussion on ocean surface skin temperature and ocean mixing.
Judith, I can’t find your response. All you siad in response to my exposition about the inability of back radiation to heat the ocean on the ‘best case’ thread was:
“I and some colleagues are working on a new high resolution satellite data set of ocean surface latent heat (evaporative), that works under conditions of extreme fluxes found in the high latitude oceans, warm currents, and hurricanes. More on this soon.”
Gissa clue. :)
Here is her response:
Dr. Curry on the Ocean and Radiation
Judith has a good response but there’s an even more important to make than the fact that back infrared radiation can heat the ocean.
That is, increasing the Co2 content of the atmosphere does not primarily increase the greenhouse effect by creating more back radiation to the surface. Rather, increasing CO2 primarily affects what’s happening higher at altitude, and the whole troposphere-surface system pretty much warms in concert as the planet becomes a less efficient emitter to space. In fact, this increase in temperature will generally cause more of the increase in downwelling IR flux than the direct increase in CO2 will– this is particularly true if the boundary layer is already a near-perfect emitter at its temperature (such as in the moist tropics). The additional downwelling IR flux is just one of many terms in the surface energy budget.
The emitter issue seems to be what the sample chapter of Greenhouse Dragon is about. I take it the boundary layer is not a “near-perfect” emitter elsewhere.
You are talking about the TOA equilibrium with the sun and space I take it. The down-welling flux into the ocean will also increase, which if I understand the mechanism correctly, will create more water vapor from the skin of the ocean. All else being equal, this in turn should produce more clouds I think. The clouds could then reflect more incoming SW back into space. This would have the effect of lowering the TOA equilibrium height. I don’t understand why the cloud feedbacks are better understood.
I don’t understand why the cloud feedbacks are NOT better understood.
Jim–
Cloud feedbacks are complicated because there is no simple relation between the amount of water vapor in the air, how much evaporates, etc and cloud cover. Furthermore, once you actually figure out if the cloud forms, its radiative effects dependent on its altitude, optical properties, and has differential day time and night time effects.
I was aware that different clouds = different effects. It just seems what with CERES data, it should have been apparent by now.
“That is, increasing the CO2 content of the atmosphere does not primarily increase the greenhouse effect by creating more back radiation to the surface.”
I don’t entirely agree with that. Just as more CO2 raises the effective height of TOA emission, it lowers the effective height of the back radiation source. These are dual, linked, effects.
Surface temperature is determined as that needed to emit (or advect) the received flux, The received flux is basically insolation (not much dependent on GHG) and back radiation. Back IR has to increase as part of a surface warming mechanism.
The TOA argument is valid too. They are connected.
Nick Stokes–
I didn’t say increasing CO2 won’t increase the downward infrared radiation, just it’s an incomplete argument in all its forms.
First off, if you keep the atmospheric temperature fixed, and put in some CO2 to an atmosphere where the low levels are radiating like an ideal blackbody, how are you going to increase the downward IR flux? The emission will be solely forced by the layers temperature in accordance with the Planck function. If the low levels are sufficiently opaque, the increase in CO2 higher up won’t increase the IR to the surface either, as it will be absorbed before it gets there. In this idealized case, the CO2 still warms the surface, but the only way to think about the problem is by bringing the TOA budget into play and allowing the whole troposphere to warm.
Then, to actually close the surface energy budget, you also need to know how evaporation and sensible heating fluxes respond, not just the radiative ones. If you moisten the Sahara desert and give it an evaporation loss term, the surface will cool even if you bump up the CO2 a bit.
Chris and Nick,
I think the missing link between your arguments and in every argument about the greenhouse effect is the different quality of the two budgets with respect to thermodynamics and the 1st law.
A flux across TOA is able to change the energy content of the whole earth system. So, TOA rules the game. A flux across the earth surface is not able to change the energy content of the earth system. Therefore, the greenhouse effect and the effect of CO2 can be explained without backradiation using the concept of emission height.
The greenhouse effect and the effect of CO2 cannot be explained without the TOA budget and the temperature gradient in the troposphere.
So, I think Chris is right, explaining the greenhouse effect only with backradiation leaves the door open and is incomplete.
Best regards
Günter
Chris,
Back radiation does not heat anything (on the average), much less the ocean. Solar radiation heats the ocean (short wave), and heats the Earth and to some extent the atmosphere. The long wave absorbing greenhouse gases and water droplets move some of the outgoing radiation upward through a series of absorptions and emissions, until they reach a height where they can emit to space from high in the atmosphere (plus some emits directly through transmission “windows”). The effective emission height sets the atmospheric temperature at that height, which then sets the temperature by way of the adiabatic lapse rate. The adiabatic lapse rate results in the ground temperature, including the ocean, to be warmer than without the greenhouse gas. The increased temperature at ground level results in more outgoing radiation than without, and the warmer atmosphere along with greenhouse gases causes back radiation, but the net difference in forward radiation and back radiation is small, with forward radiation always dominating (on the average). The outgoing convective heat transfer, including evaporation are the main source of energy transfer, and the sum of the small net outgoing radiation energy transfer and the convective heat transfer balances the solar input (unless the system is not in balance, and some storage action going on).
In other words, there is back radiation, but it is not a source of average heating, but rather a result of the combination of greenhouse gas and lapse rate as I stated. There is back radiation, but NO back heat transfer.
Thanks Jim. I see that neither Andy Lacis nor Judith Curry actually answered my points and questions. I maintain the view that back radiation is incapable of heating the ocean to any significant degree compared to solar insolation and I’ll be happy to debate it with anyone if they are interested.
The nutshell is:
1) Back radiation from the atmosphere doesn’t penetrate the surface beyond its own wavelength. A lot of its energy goes into evaporating water molecules on the surface, a cause of cooling of the surface. That energy which is mixed into the surface layer soon leaves the ocean again as freely convecting water molecules head upwards due to their lower density. The wave action which mixes solar energy down to lower levels takes place substantially further down than the level back radiation will be mixed in by light breezes.
2)http://www.terrapub.co.jp/journals/JO/pdf/5001/50010017.pdf
“Under low wind speed, the sea surface can be cooler or warmer than the subsurface due to overlying thermal conditions, and the skin layer can be neutral to the transient process between them.”
Low wind speed is the predominant mode of the marine atmosphere.
3) The ocean is on average 3C warmer than the atmosphere. The second law of thermodynamics is on my side rather than the side of those who most often invoke it to dismiss the arguments of others. Heat predominantly flows from the ocean to the atmosphere, not the other way. Atmospheric temperatures lag sea surface temperatures by 3-6 months, clearly demonstrating the direction of causality.
4) The warming of the tropical ocean by the suns energy which penetrates it to 10o metres and more during the lowered cloud albedo period 1980-1998 sufficiently explains global warming without the need to torture the data and ask the atmospheric tail to wag the oceanic dog. The rise of ocean heat content in the 1993-2003 decade calculated from the steric component of sea level rise indicates the surface forcing was ~4W/m^2 and this is much more than co2 could ever hope to achieve.
5) The net longwave radiation results in ~70W/m^2 cooling due largely to the latent heat of evaporation and the free convection of water vapour.
I, too, can’t see how the air can change the temp of the oceans much. It is easy to understand how the oceans can change air temps though. Chris pointed out that clouds/not clouds depends on factors other than water vapor in the air. That seems to leave the door open for GCRs.
My understanding is that the oceans, at depths lower than about 100mtrs is substantially cooler than the atmosphere and quite uniform from the tropics to the poles.
If the atmosphere was capable of heating the oceans, by whatever mechanism, it would have done so long ago since it’s been about 10,000 yrs since the last ice age.
Am I wrong in the above assumption?
My response was some text from my thermodynamics book. I’ll try to look for it, it is a very long post, do you remember what thread this was discussed on? I’m losing track
This is where the local search engine helps. Google provides one free but I don’t know what format the content has to be in. I am surprised that WordPress does not provide something.
Judith, Jim linked it above and I’ve answered there.
Thanks
Hi Judith: Contradicting models and theory, the NODC Ocean Heat Content data presented by Levitus et al (2009) (and as recently updated) does not indicate that there is a noticeable anthropogenic component in the warming of the oceans since 1955. To view this, simply divide the oceans into tropical and extratropical subsets.
The tropical Pacific OHC rises in “steps” in response to the increased DSR associated with the 1973/74/75/76, the 1995/96, and the 1998/99/00/01 La Niña events:
http://i36.tinypic.com/eqwdvl.png
Curiously, tropical Indian Ocean OHC mimics part but not all of the variability of ENSO until the mid-1990s. It then shifts and becomes much more variable:
http://i35.tinypic.com/2pphbf4.png
But if we combine the tropical Pacific and Indian Ocean OHC, the long-term relationship with ENSO returns:
http://i38.tinypic.com/25hdezk.png
The major increases in Tropical Atlantic OHC appear as lagged responses to the 1973/74/75/76 and 1998/99/00/01 La Niña events. The trend is the influence of the North Atlantic which represents more than 30% of the rise in OHC since 1975:
http://i38.tinypic.com/2me2vc1.png
The trend of the extratropical South Pacific OHC is reasonably flat from the early 1970s until the 1997/98 El Niño, when it rises in a step. Note the earlier spikes during La Niña events:
http://i37.tinypic.com/2vhvkwi.png
The vast majority of the rise in extratropical North Pacific OHC occurs the late 1980s to early 1990s:
http://i35.tinypic.com/s3j1h1.png
This coincides with a shift in SLP.
The South Indian Ocean rises in response to the 1973 thru 76 La Niña, dips and rebounds in the early 1990s (curiously the only noticeable reaction to the eruption of Mount Pinatubo), and then shifts drastically higher during the 1995/96 La Niña and 1997/98 El Niño:
http://i34.tinypic.com/hrwuva.png
The North Atlantic OHC is governed by SLP, AMO, and ENSO:
http://i35.tinypic.com/10nb42t.png
I discussed and illustrated the preceding in three posts:
http://bobtisdale.blogspot.com/2009/09/enso-dominates-nodc-ocean-heat-content.html
AND:
http://bobtisdale.blogspot.com/2009/12/north-pacific-ocean-heat-content-shift.html
AND:
http://bobtisdale.blogspot.com/2009/10/north-atlantic-ocean-heat-content-0-700.html
Thanks Bob, I am sending this one to Peter Webster also
The issue is whether they warm by absorbing incident solar radiation, or by absorbing secondary LW radiation from the surface. I say the former, and there is no bouncing and amplifying of heat between the surface and the atmosphere.
OT – tallbloke, if you find Judith’s response, could you please leave a map?
http://judithcurry.com/2010/11/26/raising-the-level-of-the-game/#comment-15904
I can’t help being bothered by the idea that anything is beyond skepticism. For evidence, I invoke the memory of Heisenberg. As nasty as the AGW situation has gotten, I don’t know that it approaches what went on with Heisenberg and Schroedinger. Imagine the necessity of convening all the great physicists of today in one place to have a intellectual slugfest over one issue, neuron to neuron, synapse and dendrite to synapse and dendrite. And then having the resolution be …… you’re both right! Hmmmmm, could be lol.
Try this for the GT paper:
G&T Paper
“We need to raise the level of our game in terms of explaining the planetary warming by infrared absorption of CO2 etc. “
Do you consider people as ever being responsible for the opinions they hold? I presume you’re aware there are a large number of people who hold anti-scientific viewpoints on things such as vaccinations and evolution.
At what point (if any) does the responsibility shift from the scientist to communicate and for the skeptic to listen? Even going one-to-one do you think you could actually change the minds of people posting on this and the other thread who say the greenhouse effect is impossible?
Sharpen up and read the Miskolczi paper. This is peer reviewed science.
That’s not relevant to the question I posed, see the part about listening.
Sharper’s is the fundamental question laid out by this post: is the problem with these “erroneous” papers a something that could be remedied by a lesson accessible to by “an audience that has taken 1 year each of undergraduate physics and chemistry, plus calculus,” or is it ideological in nature?
The premise of this is as flawed as the notion of “Global”.
The climate system is Not static nor will it ever be homogeneous due to all the non-linear aspects and dynamics.
The idea, to understand the issues requires Indoctrination is a fallacy.
Climate Science has failed to communicate because it attempts to define “Global” without proper diligence to the regional aspects of the system and without clearly stated deference to its current limitations.
I presume you’re aware there are a large number of people who hold anti-scientific viewpoints on things such as vaccinations and evolution.
Obviously I’m not Dr Curry, but I think it’s relevant to note that this large number of people with an anti-scientific POV is a minority of the US population; I think the far right anti-evolution “evangelicals” comprise under 20% of the GOP (don’t have the cite for this handy, sorry, but this came from Time or Newsweek some time back), which puts them at some 10% of the US population at best. And even then, many are not anti-science since they object to only that which challenges beliefs, which then reduces this number where it concerns the subject at hand. The GHE doesn’t directly challenge biblical belief the way evolution does.
Your comment is biased, prejudicial and not helpful.
The Miskolczi 2010 abstract:
THE STABLE STATIONARY VALUE OF THE EARTH’S
GLOBAL AVERAGE ATMOSPHERIC PLANCK-WEIGHTED
GREENHOUSE-GAS OPTICAL THICKNESS
by Ferenc Miskolczi
Published in: ENERGY & ENVIRONMENT SPECIAL ISSUE: PARADIGMS IN CLIMATE RESEARCH
VOLUME 21 No. 4 2010, AUGUST
ABSTRACT
By the line-by-line method, a computer program is used to analyze Earth atmospheric radiosonde data from hundreds of weather balloon observations. In terms of a quasi-all-sky protocol, fundamental infrared atmospheric radiative flux components are calculated: at the top boundary, the outgoing long wave radiation, the surface transmitted radiation, and the upward atmospheric emittance; at the bottom boundary, the downward atmospheric emittance. The partition of the outgoing long wave radiation into upward atmospheric emittance and surface transmitted radiation components is based on the accurate computation of the true greenhouse-gas optical thickness for the radiosonde data. New relationships among the flux components have been found and are used to construct a quasi-all-sky model of the earth’s atmospheric energy transfer process. In the 1948-2008 time period the global average annual mean true greenhouse-gas optical thickness is found to be time-stationary. Simulated radiative no-feedback effects of measured actual CO2 change over the 61 years were calculated and found to be of magnitude easily detectable by the empirical data and analytical methods used. The data negate increase in CO2 in the atmosphere as a hypothetical cause for the apparently observed global warming. A hypothesis of significant positive feedback by water vapor effect on atmospheric infrared absorption is also negated by the observed measurements. Apparently major revision of the physics underlying the greenhouse effect is needed.
Is that the same Energy and Environment journal that is thought by some to be rather biased in its approach to publishing? I believe the editor said “I’m following my political agenda — a bit, anyway. But isn’t that the right of the editor?” and “Roger Pielke Jr said in a post answering a question on Nature’s blog in 2007 about peer-reviewed references and why he published in E&E: “…had we known then how that outlet would evolve beyond 1999 we certainly wouldn’t have published there. The journal is not carried in the ISI and thus its papers rarely cited. (Then we thought it soon would be.)”
from http://en.wikipedia.org/wiki/Energy_%26_Environment
There are peer reviewed papers and then there are peer reviewed papers.
Judith commented on E&E previously here http://climateaudit.org/2007/11/15/craig-loehle-reconstruction/#comment-118361
“Re E&E. The reputation of a journal rests in the number of citations it receives, the scientific stature of its editorial board, ts reputation for fair and critical reviews of papers, and its selectivity. E&E scores very low on all of these (with possible exception of the review process, i simply don’t know). Further, based upon their public statements, many of the editors of E&E have an overt agenda with respect to energy and environmental politics. Hence choosing to publish a scientific paper in this journal taints the paper and the author as being driven by a political rather than a scientific agenda.”
Are you sure you want to start a debate on the bias of journal editors?
Nature didn’t publish a solar paper for 5 years.
Steigs paper on the melting antarctic?? Lol.
Science Journal bias is a great target of opportunity for skeptics. Those pesky e-mails and the documented behavior of many AGW promotion journals is well documented.
But does any of that matter? Does it really matter who funded the research or who published it or for what reason it was published? Let’s look at the content. Is it solid or not and why?
On two fronts, it does matter who funded the research and where it is published to an extent. On the other, the science itself is pretty unbelievable on first glance.
The basic premise to Miskolzci’s theory is that the atmosphere ‘knows’ how and when to condense water in order to preserve a particular value of its IR optical depth. There is no physical process that he posits or observes in reality to tell him this other than what he presumes is solid humidity data from several decades ago. All of that despite several leading scientists have told him this data is flawed.
More than that, from a molecular point of view, his theory goes against the laws of thermodynamics. Because water is at a much higher concentration in the atmosphere than other IR absorbing gases that can condense, say acetone, it will take a tremendous amount of water condensation to make a small change in the IR transmission through the atmosphere. Since processes that use the least amount of energy are favored throughout physics, it would seem that the atmosphere ‘would want’ to condense greenhouse gases that are at a much lower concentration than water and absorb IR light inside the water ‘window’. That would maintain the IR optical depth at a specific level while spending less energy overcoming inter-molecular forces in the condensation process.
But none of this is explored nor explained by Miskolczi.
Moreover, because his theory is so vague that it doesn’t define which regions of the IR spectrum are important in these processes, there isn’t a real way to falsify it in the lab, where nothing like what he describes has been observed. Maybe you could convince the guys at JPL molecular spectroscopy lab to take up this cause, but I’d suspect you’d have a hard time getting anywhere with that.
Based on all this I’d say the fact that his work is published in Energy and Environment means it’s garbage.
Miskolczi could not even recognize the difference between emission (a flux of energy) and emissivity (a ratio), at least in one of his original papers a couple of years ago. There’s just so much wrong with his idea, but observations themselves show it to be wrong (just like with Claes Johnson’s paper which states that back radiation is implausible…yet it’s observed everyday). Just stupidity.
The guy was in an $80K job with Nasa as a physicist. His Boss logged into his computer with his credentials and pulled his paper from JGR. That’s why he resigned and published in E&E
http://tallbloke.wordpress.com/2010/01/04/why-the-sun-is-so-important-to-climate/
I see all the usual prejudice being trotted out here.
“what he presumes is solid humidity data from several decades ago. All of that despite several leading scientists have told him this data is flawed.”
If the data is so bad why does this neat correlation appear between specific humidity at the tropopause and solar activity levels?
http://tallbloke.wordpress.com/2010/08/08/interesting-correlation-sunspots-vs-specific-humidity/
It seems that all the data which mitigates against the AGW hypothesis (radiosonde, ISCCP) is flawed, while treemometers and dodgy stats algorithms like Manns reworking of PCA rule the roost.
Zero credibility.
‘If the data is so bad why does this neat correlation appear between specific humidity at the tropopause and solar activity levels?’
Most likely coincidence. Without your proposing a physical model that would explain such a correlation naturally, why should we believe it to be anything but a coincidence?
I think it’s also unfortunate that you are conflating a serious critique of the physical model that Miskolczi presents with an acceptance of any and all other techniques and models. No one mentioned anything about paleoclimate or thermometers or any other measuring devices before the satellite era. You’re simply inferring that because people are not wholesale accepting what you claim.
Make a better argument then maybe you can start making remarks about others’ ‘credibility’.
“No one mentioned anything about paleoclimate or thermometers or any other measuring devices before the satellite era. ”
You cast doubt on the radiosonde data from 1948. No satellites around then.
“Without your proposing a physical model that would explain such a correlation naturally, why should we believe it to be anything but a coincidence?”
I could say the same about co2 and temperature. But then, they don’t correlate as well as solar activity and specific humidity at the tropopause do they?
And I do have a physical model for that correlation, but this is not the thread for it.
bloke,
‘You cast doubt on the radiosonde data from 1948.’
Yes, Miskolczi’s theory necessitates a discussion of the utility of radiosonde data. What does that have to do with other measurement techniques that deal with your claims about others’ ability or inability to accept what you have to say?
‘I could say the same about co2 and temperature.’
Huh? The atmospheric greenhouse effect is a testable and proven model for a causal relationship between temperature and CO2 concentrations in the atmosphere. It’s based on quantum mechanics, arguably the most well tested scientific theory we have come up with yet. So I don’t understand where you get the impression that there isn’t a meaningful physical model relating CO2 concentrations and temperature. It’s called the Beer-Lambert law.
I do agree that an increased greenhouse effect doesn’t explain ALL the variation we’ve seen in surface temps, but that’s hardly a reason to doubt whether the atmospheric greenhouse effect is a physical model.
My doubt concerns the application of theoretical physics to the real atmosphere, the quantities derived, and the assumption that a significant amount of extra IR energy makes it’s way into the deep ocean from the atmosphere.
Ever tried warming up a cold coffee with a hairdryer?
Maxwell
“Miskolczi’s theory necessitates a discussion of the utility of radiosonde data.”
Any references on how to quantitatively correct the radiosonde data?
Otherwise Miskolczi used it as the only 60 year data for humidity available.
Are you sure you want to start a debate on the bias of journal editors? :)
And Wikipedias less than even handed approach to climate change??
Two things that bother me about the way the greenhouse effect is explained have to do with description.
Many people, including NASA and NOAA, claim that greenhouse gases ‘trap’ heat in the lower parts of the atmosphere. That is an oversimplification, however. Because CO2 or CH4 can absorb earthlight and re-emit it back toward the surface, the amount of time that energy stays in the lower portions of the atmosphere increases. But it doesn’t increase to infinity, as is implied by the word ‘trapped’. As a molecular physicist, I think it’s imperative to make sure that the dynamics of each molecule come through in these mechanistic explanations. The lifetime of a vibrationally excited state of a gas phase molecule is on the order of a millionth of a second, if not shorter. That’s hardly trapping.
Also, I agree with a couple other physicists here that there is a bit too much oversimplification in the picturing of these processes. The idea that the climate started at ‘equilibrium’ may be useful as a pedagogical tool, but it does little to help explain the observed data we have. That is, there is a ~1% difference between the incoming and outgoing radiation at the top of the atmosphere as measured by satellites. Most of that 1% is purportedly due to the increased greenhouse effect due to human influence. However, such a conclusion is based on the assumption that before such satellite based measurements were made this difference in incoming and outgoing radiation was exactly 0%! I’m not sure how good on an assumption that is.
From my perspective, the best analogy I’ve read so far came from Roy Spencer who compared the atmospheric greenhouse effect to a blanket. Putting a blanket over your body impedes heat from being emitted out to the surrounding air. That ‘excess’ heat causes your clothes and the blanket to heat up until the rate of the energy in (from your body) equals the energy out (from the blanket to the air). By adding CO2, we make the ‘blanket’ more insulating such that the temperature has to increase to increase the rate of energy loss to ‘the air’ (space).
Is that the only thing at play in climate? Of course not, but it’s hardly disputable physics.
As far as Venus is concerned, the greenhouse effect is very large there, but more importantly, the Coriolis force on Venus is very small. There are only two days per year on Venus. Since the Coriolis force is responsible for a great deal of the atmospheric dynamics on Earth, the large difference in day length makes comparisons between the two planets difficult at best.
Thanks for the technical thread.
If there is a ~1% difference between the incoming and outgoing radiation at the top of the atmosphere as measured by satellites wouldn’t we be able to measure the differences over the last 25 years and correlate the difference to the changes in atmospheric GHG’s?
Rob,
Sure. People have done that. Trenberth was the first (?) in the late 1990’s, but the noise in the measurements is pretty big. Almost the size of the actual measurement itself. So it’s hard to say definitely whether it’s +1%, +0.5% or some slightly smaller or larger number.
But even if we had a real concrete measurement, how do we know what the difference between the incoming and outgoing radiation ‘should’ be? From my perspective, this is where the assumption of climate ‘equilibrium’ comes in. It seems implicitly assumed that ‘equilibrium’ means that this difference must be zero. But surely there are fluctuations in this difference due to internal variability (ENSO, Arctic oscillation, etc.) or other factors (people). So what time scale ‘should’ we have to integrate over to get zero explicitly in an ‘equilibrium’ situation?
I don’t know the answer to that question and I would posit that no one does for sure right now.
But I think as time goes on, we’ll have more and more data to say how that number (radiation difference) is changing and get a better idea of how a human forced increase to the greenhouse effect is changing the energy landscape of the planet.
I would not think the equilibrium issue is really key, since it is a notional concept at best. I would have thought that being able to determine if the difference between incoming and outgoing radiation changed at a rate consistent with the changes in GHG’s, it would potentially confirm or refute positions such as those made by Huffman in an earlier post.
The data isn’t good enough yet to know at what rate the net radiation flux of the top of the atmosphere is changing. As I said before, even if we did have good enough data, it would still be a hard sell to claim that the data confirmed anything at this point because the physical models of the climate do not make specific enough predictions to make meaningful use of such observations. Such models would have specifically predict what ‘equilibrium’ meant in an observational sense.
Also, how many different ways can our current physical climate models give a +1% difference between the incoming and outgoing radiation fluxes? I’d bet it’s more that one.
I wonder if the climate researchers have considered that the difference between the incoming & outgoing radiation has always been there, & is due to the Earth’s internal heat being transferred to the atmosphere? Or did they just jump to the conclusion that our CO2 emissions were the cause?
“So what time scale ‘should’ we have to integrate over to get zero explicitly in an ‘equilibrium’ situation?”
About as long as it takes the solar system to traverse one of the galaxy’s spiral arms and the space between that and the next one.
http://tallbloke.files.wordpress.com/2010/11/shaviv-n-the-milky-waygalaxys-spiral-arms-and-ice-age-epochs-and-the-cosmic-rayconnection.pdf
bloke,
‘About as long as it takes the solar system to traverse one of the galaxy’s spiral arms and the space between that and the next one.’
That’s ridiculous. You’re saying that we have to integrate over millions of years to get a meaningful understanding of the internal and naturally variation in climate on earth to the first few orders?
The very nature of the problem is set in time scales that are less than a ten of a percent of that time period. How can variations with time scales on the order of millions to ten of millions of years substantially affect processes that occur on decade to century time scales? That’s basically the same as saying that the behavior of an excited molecule will depend on which side of the lab I do a measurement.
It doesn’t.
If the period of interest were that long, integrating over 1000 years would provide a constant background to the galactic variations, meaning that it would still be useful to us on a day to day basis. More than that though, what you’re proposing is impossible given the fact that the chances civilization lasts that long are close to zero.
So I would conclude that looking at variations that occur on time scales less that hundreds of millennia does not necessitate accounting for galactic variations. Our galactic background is not fluctuating fast enough to matter on ‘interesting’ time scales.
OK, I was taking the longest climatic variation we can identify to make a point. However, there is evidence, and some glimmering s of mechanism to elucidate climate cycles which occur on timescales which do affect our interpretation of climate trends happening now.
For example, there is an apparent warming and cooling taking place on a millenial timescale, evidenced by archaeological finds on Alpine passes in Europe, where Roman and medieval artifacts have been discovered recently at locations impassible between these periods and between medieval and now. From medieval times there was a descent in temperature to the little ice age, and then rising temperatures to today. This rising trend coincides with an increasingly active Sun from 1670 to 2003. We now seem to be entering a period of solar grand minimum potentially as deep as the Maunder minimum in the C17th. Other solar minima intersperse the deeper ones, with a periodicity in the ensemble of around 180 years.
The work of Charvatova links these periods with the motion of the Sun wrt the centre of mass of the solar system. The mechanism may involve the disruption of the solar dynamo by these irregular motions.
A way to explain the basic effects to a lay audience might be to do a thought experiment starting with an atmosphere with no GHG and then to add just 1 test molecule of a GHG and give a detailed explanation of each additional process which that one molecule can participate in, showing how each process is consistent with Quantum Mechanics, Newton’s Laws and the 1st and 2nd Laws of Thermodynamics, dealing with the various popular objections as you go, while increasing the concentration of the GHG from 1 to 2 to many.
JT,
that’s a great idea. Unfortunately, once you begin mentioning vibrational degrees of freedom of GHG molecules, eyes begin to glaze over. That might even be true in the climate science crowd as much as it is considering a lay audience.
I think the larger point is that those who posit ‘alternative theories’ to the atmospheric greenhouse effect will do whatever they can to convince themselves (and possibly others) that something makes the greenhouse effect wrong. I don’t think that Dr. Curry’s point about poor communication is valid in this case. People just don’t want to believe that it could be true.
Maxwell,
As a molecular physicist perhaps you could help me to understand how the energy from molecular H2O condensation (latent heat) is transferred away from the H2O cluster?
There are only 2 mechanisms – radiation and conduction. Radiation I can understand, although I would like to know the most probable wavelength this would occur at (I could see it being a range of frequencies, depending on the nature of the H bond formed and the cluster size).
What I am stumped by is how conduction could be a direct transfer process. My thinking is that the energy must be released immediately in order for the H bond to form. If it does need to be released immediately, then I cannot see how conduction would work. Is it possible that the latent heat energy is stored in the molecular cluster – perhaps distributed throughout momentarily until such time as a collision with another molecule occurs, for example N2 or O2, to transfer it?
The mechanics of evaporation makes sense to me, but condensation does not.
Kan,
I’d think it would have to be collisions with other gas phase molecules while the water molecules themselves were near other water molecules (condensation is not a single molecule process) or collisions with clusters of ‘stuff’.
My guess is that the second process plays a larger role in condensation just based on contrails from airplanes. For example, the ‘large’ material particles in the jet exhaust immediately cause the highly concentrated water vapor to condense. This process is known as nucleation and is at the heart of many processes like condensation, i.e. micro/nanofabrication growth, crystal formation, etc.
I’d also guess that since these ‘large’ material particles have many, many degrees of freedom, it’s not hard for them to absorb the energy necessary for the condensation of some water molecules. I don’t know how many ‘some’ is, however. But then again, we’re now talking about cloud formation, which may be the most uncertain physical process in climate science.
Hope that helps.
Judith,
I come to this very much as an outsider, so this is really two questions.
Surely it makes no sense to claim the greenhouse effect exists, but place no limits on its magnitude – the size of the effect could be infinitely small, or is the greenhouse certain to have a value of at least (say) 2 deg per doubling in the absence of feedback effects?
I mentioned in an earlier comment the analogy with Venus’ atmosphere, and I wonder if the temperature at 1atm pressure in that atmosphere (far more moderate that the surface temperature at ~92 atm) could be used to estimate the actual size of the greenhouse effect.
David, you appear to be talking about the so-called enhanced greenhouse effect due to increasing greenhouse gases such as doubling CO2. This thread is actually about the primary greenhouse effect, which supposedly makes earth habitable in the first place.
Well surely from a scientific point of view, the basic greenhouse effect and any enhancement due to extra CO2 are the same thing – we are just altering one parameter.
No, these would be the same thing is you assume that the effect dependence on the parameter is monotonic with altering its “concentration”. It is quite possible that the dependence reaches a plateau or has other kind of inflection point. That’s why conflating the primary effect with “sensitivity” is wrong and confusing to many.
Good explanation and discussion here too http://www.skepticalscience.com/argument.php?a=164
thanks, i’ve added this one
Watch out for strangely recalibrated Y axes on that website.
There are three fundamental problems with the greenhouse model as an adequate model.
1) The pure physics only gives a coherent answer in a pure gas without clouds. On top of this, how the surface albedo varies with space and time is maddenly complex. Thus when IPCC supporters say “it is radiation physics you dolt” they are either ignorant or disingenuous. Pure physics does not allow calculations in such a spatially complex system. As I have mentioned before, strain and fracture in pure substances is well-characterized and used by engineers all the time–so why can’t we predict earthquakes? It is the heterogeneity and scale that prevent us and this applies to the atmosphere also.
2) The “pure physics” even if adequate only give 1 deg C or so of warming for a doubling of CO2 from historic levels. The rest is the famous unproven (and assumed) water vapor feedback. If your entire argument of doom is based on a hand-waving assumption, don’t expect anyone to join you in your hysteria.
3) The problem of figuring out heat transfer in a complex multifluid is quite intractable. We know the GCMs don’t handle thunderstorms well as heat pumps. In addition, let us say that part of the process of ENSO type systems is concentrating or dispersing surface warm/cold waters. If warm waters concentrate at the surface, more heat might radiate to space, and conversely when heat mixes rather than concentrating at the surface. How do we handle/compute this? Not “pure physics” at all.
Thus the problem is not just physics but that the heterogeneity and turbulence prevent nice analytic solutions and may create unexpected outcomes.
strain and fracture in pure substances is well-characterized and used by engineers all the time–so why can’t we predict earthquakes?
Um.
Very funny–that’s a prediction? How about when and where closer than “california within 30 yrs”. Thanks for making my point.
That’s your point? Climate predictions are vague in the same way earthquake predictions are vague, for the same reason: the complexity, which you correctly pointed to in your comment.
The complexity doesn’t stop scientists from saying “The likelihood of a major quake of magnitude 7.5 or greater in the next 30 years is 46%” and shouldn’t stop scientists from saying “that climate sensitivity is likely to be in the range of 2 to 4.5°C with a best estimate of about 3°C.”
PDA,
Of course both the climate predictions and the earthquake predictions are right; they both are based upon models. Everyone knows that computer models can’t be wrong!!
Good own goal there, PDA!
Haw haw haw AllenC, ya got me. Yes, computer models can be wrong, as can everything else.
I agree that the way forward is to leave aside any idea how to quantify the correctness of simulations, and how to incorporate additional evidence from direct observation. Rather, let’s just continue to guffaw “COMPUITR MODOLZ R TEH ST00PID!!1!”
This is citizen science at its finest.
If you think the unverified predictions of earthquakes (47% blah blah) are good enough and such vague predictions are good enough for climate change, this is NOT what the alarmists are claiming, they are claiming certainty of disaster. It is possible to MAKE earthquake predictions, but their track record of being right is vanishingly small.
I don’t live in California, but don’t they have more restrictive building codes there because earthquakes are more frequent, and shouldn’t we apply the same thinking to the damage that could be caused by warming?
Damage by earthquakes has been observed for centuries. Damage by CO2 induced heating is still only a hypothesis.
Craig, none of these issues are ‘problems with the greenhouse model’
No one argues that cloud aren’t complex, but they are still physics problems. There are many issues at the interface of dynamics (e.g., what is forcing the air to rise or sink), thermodynamics (e.g., the availability of water vapor), and microphysics, and a fundamental issue is that it’s computationally expensive to model everything relevant at the scales necessary to resolve the finer details. But the fundamental ways the greenhouse effect works is still at play with clouds. They interact with radiation in understood ways, and just because they have an albedo component doesn’t mean the ‘greenhouse’ component is invalid.
Your statement about water vapor feedback just reflects you are ignorant of observations, theory, or how we have come to learn about the water vapor feedback (hint, it’s not “assumed”). Similarly, water vapor distribution is also a ‘physics problem’ (what else would it be, astrology?). Just because something is a feedback, or not part of the “CO2-only” response, doesn’t make it any less valid.
You’re just making things up.
Craig, you write ” The “pure physics” even if adequate only give 1 deg C or so of warming for a doubling of CO2 from historic levels.”
I have no quarrel with what you have written, except for this sentence. I object to the alleged 1C rise for doubling CO2. This number has never been measured. This number can never be measured, since any attempt to do so would be coufounded by any feedback effect. I queried the physics used by the IPCC to estimate this number, and I believe Judith agreed with me that this physics leaves a lot to be desired. There seem to be a number of oversimplistic assumtions made in order to arrive at the number.
But, if the number can never be measured, it must always be subject to the Kelvin Fallacy, and we simply can never know for sure what the number is. And this will never change.
The number of 1C for a doubling of CO2 is much more science fiction than it is physics.
I agree that the no-feedback sensitivity can never be observed (unless one day we make a laboratory Earth) but it can be worked out on the back of an envelope and there are really no big assumptions that go into it. It is, for instance, not at all dependent on the land surface physics and is almost entirely constrained by the radiative forcing for CO2 (which can be measured). It’s also a value of virtually no spread amongst climate models which do more than back of the envelope. It’s one of the easiest pieces of physics in this discussion and can amount to a simple derivative of the Planck function, so I don’t see a reason not to believe it.
Chris Colose writes “I agree that the no-feedback sensitivity can never be observed (unless one day we make a laboratory Earth) but it can be worked out on the back of an envelope and there are really no big assumptions that go into it”
Lord Kelvin worked out that the age of the earth was 10,000,000 years. He used a similar sort of method as you described for estimating global temperatures. He claimed he was right because he had taken into account “all known factors”. In fact the earth is 4.2 billion years old. That is why we call it the Kelvin Fallacy.
I am sorry. If you cannot measure a number, then you have no idea what that number is. Period. That was the physics that I had hammered into my head 65 years ago when I studied Physics 101. It was true then, and it is still true today.
Since when has climate science ever bothered to worry about observations?
Any data that doesn’t agree with the latest theory is ‘adjusted’ until it does. I believe that guys in New Zealand are especially good at this, followed closely by UEA/CRU.
They must be brassed about coming second, since they trained Jim Salinger in the first place.
In fact the earth is 4.2 billion years old.
But I thought “If you cannot measure a number, then you have no idea what that number is.” No idea. “Period.”
It would probably have been better if your Physics professors had not used a hammer.
Sorry, PDA, I have no idea what you are talking about. Ernest Rutherford, as a research student from New Zealand, provided the measured data that proved that the earth was 4.2 billion years old.
Ernest Rutherford, as a research student from New Zealand, provided the measured data that proved that the earth was 4.2 billion years old.
I have no idea what you are talking about. Rutherford was at McGill (which – at least on the Earth I am writing from – is in Canada) when he made the discoveries about radioactive decay that led to the practice of radiometric dating.
In 1929, Rutherford estimated the Earth’s age, in “Origin of Actinium and Age of the Earth,” as 3.4 billion years. It wasn’t until 1953 – 16 years after the death of Rutherford – that scientists began to approach within a billion years of today’s best estimate of 4.55 ± 0.02 billion years.
These are estimates of the Earth’s age, based on analyses of the lead isotope ratio in very old rocks like meteorites. They are not “measurements.”
Rutherford was born in New Zealand. The original sentence was ambiguous. You are both right.
Sure, if you want to interpret the sentence as “Ernest Rutherford, as (a full professor in Canada who was once) a research student from New Zealand, provided (an essential discovery about radioactive decay that when combined, decades after his death, with) the measured data that (was collected by another researcher) proved that the earth was 4.2 billion years old” then yeah. We’re both right.
Is it coffee time or cocktail time in your time zone? Suggest that you have a stiff one anyway, and chill a bit.
Rutherford was a native of New Zealand who was working in Canada at the time he performed the work described. It is not wrong to say ‘a researcher from New Zealand’. Nor is it wrong to add ‘working in Canada’
You are both right. Cool it (if that is still possible in these globally warmed days).
In snowy Surrey UK winter has come at its earliest for about twenty years. And we are all laughing our butts off watching the Loonies in Cancunies screaming at us that we’re forever doomed to perpetually warmer winters. Bring them on!!
“Student” was wrong, as was the attribution of the estimate of Earth’s age to Rutherford, as was the estimate itself.
I’m perfectly cool. It doesn’t upset me one bit to have these sorts of disagreements with strangers, but if it upsets you, I certainly think your Rx is a good one to self-administer.
If this is meant to imply that the geological age of the earth cannot be measured (with error bars) then you are plain wrong – try half-life timespans from various elements found in meteorites
And actually, Professors of Geology use geo hammers :)
PDA Fair enough. However, it does not take away from the Kelvin Fallacy. Kelvin did the calculations, and he was wrong. That is the key point. That is why the estimations for a change in global temperatures may be subject to the Kelvin Fallacy, and are, therefore, totally unreliable.
Rutherford did the calculations, and he was wrong. Does that mean radiometric dating was “totally unreliable?” Of course it doesn’t.
The “point” that scientists have been wildly wrong in the past and so could be wildly wrong about global warming now is both trivial and irrelevant. Of course they could be wrong. Everything we think we know is subject to revision.
Unless you point out the specific errors, though, just repeating “well, they could be wrong” ad nauseam is mere handwaving.
PDA, you are missing the point. If you have replicated measured data, there is no question of who is right or wrong. The measured, replicated data is right. That is what the “scientific method” is based on.
What I am pointing out is that the proponents of CAGW have little replicated measured data to support the hypothesis of CAGW. Craig put up this myth that doubling CO2 causes global temperatures to rise 1 C with no feedbacks. This number can never be measured, and so is completely measingless. As are any other numbers which cannot be measured.
I am not “missing” the point. I am disagreeing with it.
The age of the Earth is a physical property that can not be “measured” in any realistic way. We have no ‘timers’ dating from the moment of the cooling of the molten planetary mass. Its age can, however, be estimated with a fair degree of accuracy thanks to our understanding of radioactive decay.
Likewise, the effect on mean global temperatures of a doubling in carbon dioxide concentrations in the atmosphere is a physical property that cannot be measured. It can, however, be estimated. I’d say that the accuracy is roughly commensurate with that of geology at the same stage of development. Most of his contemporaries thought Kelvin was way underestimating the age of the Earth, by the way.
Reasoning by analogy breaks down at a certain point. If you have criticisms of how climate sensitivity is calculated, be specific about them. But leave poor William Thomson’s ghost out of it, please.
Back of the envelope climate sensitivity.
Change in no feedback temp of CO2 = 5.35xln(540/270) = 1.2C
Change in temperature = change in no feedback temp of co2/(1 – feedbacks)
Feedbacks = (water vapor (+/-) albedo (+/-) lapse rate (+/-) clouds)
Best empirical observations = WV = +0.6, albedo = +0.1, lapse rate = -0.3 clouds = +.15
Change in temp = 1.2/ (1 – .55) = 2.7 C
Climate sensitivity per doubling of CO2 is 2.7. When error bars are included for the feedbacks, the range is likely between 2C – 4.5C with 2.7 being the most likely.
Gryposaurus, where did you get the 5.35xLN{}=1.2C from?
5.35 is the radiative forcing of CO2 based of thousands of lines of atmospheric satellite data calculated by Myhre 1998. LN is the natural logarithm. And 540/270 is the CO2 doubled and original CO2.
540/270 = 2
the LN of 2 = 0.69
5.35 x .69 = 3.7 watts per square metered
= 1.1C +/- .1 with error bars
Chris Colose, please do us skeptics a favor and derive for us the 3.7W/m2 forcing from 2xCO2 on the back of an envelope. I would be also tremendously interested how do you propose to measure it. Please.
This isn’t quite a back of the envelope calculation. You need something along the lines of line-by-line radiative transfer calculations that go through the absorber and temperature profiles and the spectral selectivity of the gases in question. I don’t do this! but Andy Lacis could probably go through this process with you, he did so in some degree in this comment on my blog …also see the Myhre et al 1998 results. Note that this is the forcing, not the temperature change.
“Modeling radiative transfer in the Earth’s atmosphere is a bit messy and complicated, if not outright murky and opaque.” – A. Lacis
“… three vertical profiles (a tropical profile and northern and southern hemisphere extratropical profiles) can represent global calculations sufficiently. These profiles are used for all calculations in this study” – Myhre et al. GRL(1998)
Thank you Chris Colose. Whole three near-tropical profiles, I understand. This must be definitely representative, especially for polar areas. Thanks.
Am I being super-dumb here or could you not conduct an experiment something along the lines of taking a large volume of air w/o any GHGs apart from CO2. Measure its properties. Double the proportion of CO2 and measure again. That will give you a base understanding of the warming just due to CO2. Then introduce various amounts of different other GHGs and you can measure the ‘feedback’ due to each…and in any combination you deem useful.
Not an ideal experiment, I concede, but it probably doesn’t require anything nearly as expensive or difficult as the LHC…and it would give some raw numbers that seem to be so sadly lacking in the whole field of climatology.
It would require some passing facility with experimental techniques rather than just sitting in a computer suite like Harry tearing his hair out, but maybe some passing chemist or experimental physicist could help out in their tea breaks. And they could borrow a statistician to help them interpret the results.
It would be very easy to demonstrate that CO2 emits at, for example, 15 microns in proportion to its amount and temperature. This is also easily seen with the IR spectrometer looking up at the sky. I don’t think the skeptics believe in experimental evidence like this, however, or perhaps they just don’t know about it.
Well I used to do quite a bit of IR spectrometry as part of chemistry. Its a useful way of helping to find out something about what that funny white organic powder you have just made. So I’m tolerably familiar with the principles, thanks for asking.
If you tell me that CO2 emits in the IR at 15 microns, I’m more than happy to believe you. You could even show this on national TV to convince people by tuning an IR camera to that wavelength and wave it around a bit.
But its a waaay long stretch from that to positive feedbacks of 4x or more and hence frying tonight. And very little measured experimental data around. That tells me that theory is in a very primitive state when stood against the norms of ‘proof’ needed in hard science.
My suggestion is a way to focus in on the key issues and do some freaking measurements. This would avoid the Kelvin fallacy. And restore some scientific credibility to the tattered field of climatology.
Would it satisfy you to see clear sky emitting 250 W/m2? For feedback, it is hard to imagine any better experiment than warming some water by a degree and seeing if the vapor above it increases in an amount that maintains its relative humidity, which is saturated at the surface. This is what we are doing to the oceans.
Hi Jim D
It would be a useful starting point. But by itself it proves only exactly what it measures…a point the learned Jim C was trying to make above. Once you feed that number into a theory (I guess the overall radiation balance), then you have to look at the theory as a whole..not just the individual bits and come up with ways to prove the overall theory.
I had a lovely theory once upon a time when the world was young, when summers were hot and winters weren’t as frigging cold as this one (ie in the days before global warming) of a little piece of high atmosphere Chemistry. All the computer simulations gave great results..it was super. But sadly, the experiments showed that it was fundamentally wrong. We canned the theory.
You have to show every bit of the logic. And where the logic chain is weak, invent experiments to test it. Make them reproducible. Show the working. Publish the code. Test each bit individually, then a few bits collectively. (Simple integration engineering this). Record your findings in an auditable way – like in pharma or nuclear or safety-critical engineering.
Then when you have both the theory and the test data to back it up, and have withstood the best objections that the best sceptics can devise, my scepticsm will largely go away. You will have done a good job of the science.
So far…climatology scores very low on all those counts and more. The terrifying thing is that climatologists seem to be so insulated from the rest of science that they don’t realise just how poor a job they have done.
The science is a lot more solid than you think. It was mostly established prior to the AGW theory which just put those established pieces together with the newest CO2 and temperature data. No one complained about the fundamental science until the issue became politicized in the 90’s. It is clear to me that skeptic arguments are aimed at the public, not at the scientists, who they know they won’t sway.
“warming some water by a degree and seeing if the vapor above it increases in an amount that maintains its relative humidity, which is saturated at the surface. This is what we are doing to the oceans.”
But Jim, the oceans have been cooling since 2003. How does extra co2 do that?
Is CO2 expected to explain every wiggle in sub-decade periods? I don’t think so. Wait a few more years before claiming this is climate, or compare this decade with previous ones.
Is CO2 expected to explain every wiggle in sub-decade periods? I don’t think so. Wait a few more years before claiming this is climate, or compare this decade with previous ones.
Granted ENSO is a subdecadal wiggle, with an amplitude of at most 0.08 °C. However the AMO is a pretty major 60-year wiggle with an amplitude of 0.1 °C (i.e. a range of 0.2 °C). I see no sign of either kind of wiggle dying out in the next century, though AMO may well disappear for the duration of the 23rd century before returning.
Feel free to quote me if it doesn’t. ;)
Of course if our descendants are all fried by then it’s moot. My hope is that we’ll have avoided this by being mostly be on nuclear fusion power by 2060, after which the AMO warming should re-emerge from the cancelled CO2 warming which is currently almost completely masking it (but you can see it clearly if you know the trick for removing the mask).
Jim D
A parabolic mirror pointed to the clear night sky has been known to freeze water at its focal point.
When the ambient temperature arounf the dish was well above zero C
What does that tell you?
I am not sure what you think this proves. The sky’s radiative temperature is below freezing? 250 W/m2 equivalent to a cold black body, so this would be expected in that case.
Well every IPCC proponent up to now has claimed that the radiative effects of the “greenhouse effect” heats up the near Earth atmosphere.
The fact that the radiation from the sky can actually reduce the near Earth atmosphere at night has not featured in any of their explanations that I have come across so far.
The radiation from the sky does not freeze water. The water freezes, because the mirror prevents radiation from surrounding ground to warm the water. The parabolic form of the mirror allows for choosing the dominant direction of the radiation that reaches the foxal point to be one of minimal incoming intensity. The water at the focal point radiates at a higher intensity than the incoming radiation and cools.
During a clear night the amount of infrared radiation coming from the atmosphere is reduced and sufaces open to the northern sky (on the northern hemisphere) cool well below the temperature of the surrounding air. With inceased CO2 this effect is a little weaker than before, but it is still there.
Good answer Pekka the dish transmits as well as receives, but perhaps there’s more heat transfer than radiative.
The dish is still in thermal contact from the ground so local air contact and ground conduction supports the waters temperature.
However this is not sufficient to overcome the radiative interactive losses to the night sky.
In the post below as well as giving strong support to Woods experiment they report on a strange almost counter-intuitive effect (which they say has also featured in other reports).
On some cold winter nights the temperature inside the polytunnel greenhouses actually falls below the outside ambient temperature.
Its bulk features like these that make me a little sceptical of the greenhouse effect sustaining a 33C increase in the Earth surface temperature
http://www.hort.cornell.edu/hightunnel/about/research/general/penn_state_plastic_study.pdf
Jim, for your experiment heating the water, make the water body with a depth to width ratio equivalent to that of the average ocean depth versus the height of the atmosphere above it. Then heat the air volume by a degree & see how much it warms the water body. My bet is the result would be a tiny warming of the water.
You are assuming the ocean mixes the heating in a very much deeper layer than it actually does. The deep parts to play much of a role on time scales of years. A shallow ocean is a better approximation in this case.
My whole point is that I think a warming of the air will not produce much warming of either the ocean or the land if the sun didn’t shime on them.
That’s “shine” above. The atmosphere has much less capacity to carry & transfer heat than water or land. Why don’t we hear about the heating of the oceans from the Earth’s interior? After all, the ocean basins are where the crust is thinnest, & there are all the volcanics along the mid-ocean ridges. All climate science papers seem to assume the oceans are only heated from above. They surely would be colder without the heat from below. Ditto the land surface.
Yes, the sun keeps the ocean warm. If the air has more CO2 it keeps it even warmer.
Heating from underneath is not a big factor. The coldest water is at the bottom, and it stays there. We don’t see convection coming up.
Or maybe we could invent a whole new field of ‘experimental climatology’.
That would be very interesting … and could help to settle many of the fundamental disputes between the ivory-towered academics (warmists by and large) and practical engineering types (sceptics mostly) that we see on this blog.
There already is a lot of experimental atmospheric science measuring radiation spectra and such from earth and space. No surprises yet regarding the theory of those spectra. It is well established, and again skeptics don’t even know these field measurements are happening all the time.
Fine. super duper. Triffic.
Now put all that together with some air and do the measurements of what actually happens when you apply that bit of physics onto the chosen subject.
You build a chain of logic step-by-step and test each link by experiment. So far the first link – that gases absorb and emit radiation has been proved. Great. No surprises there – astronomers have been doing that for 100 years. Chemists for as long.
Only about a hundred other links to go.
You have a very odd idea of what ‘sceptics’ do and don’t believe. And why.
Read the ‘denizens’ thread on this blog. You will find that the majority of sceptics posting here are practical experimental engineering types…with lots and lots of real world experience.
And their scepticism is mostly rooted in that background. They have a healthy regard for theories…but and even healthier understanding of how far removed theory can be from practice when it gets out of the computer science lab and into real-world applications…like weather and oceans and clouds and rain and climate and stuff.
My own scepticism started when I tried to find the real experimental data behind ‘The Science is Settled’. And I was appalled to discover that there is hardly any. Just a lot of ‘adjusted’ historical data, some very dodgy statistics and a terrifyingly naive belief in unverified computer models as a substitute for real experiment.
So please don’t jump to conclusions about what ‘sceptics’ believe.
You have a strange idea of what atmospheric scientists do. The modelers, experimentalists and theorists all talk to each other to establish the building blocks. A model that did not match the observations would not last long. I see a lot of skeptics asking for observational proof, and that was what I was answering about. I can’t make you believe data, whether it is Spencer’s UAH, or Jones’s CRU, but they agree with each other independently.
In which case this entire thread is redundant. You can satisfactorily explain the raw ‘greenhouse effect’ with existing experiments.
Go ahead. Since I’ve never had a problem believing in such an effect anyway, I’m prepared to be convinced.
Like I mentioned above, measurements of 250 W/m2 from clear sky (at night) are the raw evidence for the greenhouse effect. Counter-theories fall at this observational hurdle, but still they don’t go away, but just get perpetuated on the Web and even in books.
Lets assume I want to explain to my mate Joe Sixpack exactly why your observation is a ‘proof’ of the ‘greenhouse’ effect. How would I do so? Assume Joe is an intelligent layman. work from 250 W/m2 –> therefore ‘greenhouse’ effect.
I;m not trying to be clever here…pesrsonally I don’t need convincing that there is an effect…but Joe SP might,
(We can cover climate feedbacks, ‘unprecedented’ warming, runaway warming and catastrophies…and their experimental proofs later. Let’s just start with the easy stuff).
Regarding Joe SP, this tells him that people who don’t believe in the greenhouse effect have predicted a measurement would be zero, when in fact it is 250. I think that is all he needs to know to form an opinion on those people.
PS Hell will freeze over before I believe anything at all that comes from CRU.
I read Harry_Read_Me, and as a professional IT guy it is terrifyingly amateur.
Like expecting to hear from an F1 racing team and instead meeting a kiddie with a Dinky toy and big ideas. That far away from ‘world class’. Shocking and disturbing that said kiddies are in charge of the xrawx – sorry ‘adjusted’ data on which all of AGW theory rests. And none of you guys even raise an eyebrow at their sloppiness.
Do you not understand? Not care? Or just believe that it must all be a made-up story by evil Big Oil- funded deniers?
CRU are history as far as I can tell from this press release.
Bye Bye treemometers.
http://www.leeds.ac.uk/news/article/1298/met_office_and_leading_uk_universities_launch_academic_partnership
It is no sufficient that things work in understood ways if you can’t compute it properly and have no way to test your understanding of how to handle the complexity. You say clouds interact with radiation in “understood ways” but 1) it is impossible to simulate this accurately and 2) the GCMs are at such a coarse scale that they use parameterizations of clouds, not cloud microphysics. Just because you think you understand something does not mean you can make predictions.
Craig, you specifically said in your last comment that “There are three fundamental problems with the greenhouse model as an adequate model.”
Now you are jumping to the argument that we don’t know everything about clouds or how they will evolve in the future. These two ideas don’t logically follow and is just a revision of the “we don’t know everything, therefore we know nothing fallacy.”
Chris Colose | November 30, 2010 at 5:45 pm
just a revision of the “we don’t know everything, therefore we know nothing fallacy.”
And this is the ‘all or nothing, one extreme or the other’ fallacy.
The point is we don’t know enough to model the climate in a way that enables them to be made with enough certainty to be useful as policy making tools.
Chris Colose | November 30, 2010 at 1:06 pm | Reply
Craig, none of these issues are ‘problems with the greenhouse model’
No one argues that cloud aren’t complex, but they are still physics problems.
Yes, currently intractable physics problems. Which means 90% certainty is out of the window, off the bell curve, down the plughole.
Judith
From the sceptic viewpoint looking in, it appears that climate scientists over empathise the radiative transfer of energy, almost to the exclusion of the other means of heat transfer.
Yet when I try to follow their logic there seems (to me) to be large gaps.
For instance I am led to believe that at night that radiative transfer from the atmosphere is all that stops the Earth surface from temperatures of the order of -100C
Fair enough, so I pick 15um radiation for a calculation of probabilities.
Picking an atmospheric temperature of 243K, I do a probability calculation using Maxwell Boltzmann statistics.
Absorption by CO2 of 15um from the Earth surface is very likely since virtually all CO2 molecules will be in translational mode only.
The extra energy absorbed is shared out by collision with mainly N2 and O2.
However emission due to subsequent collision is highly unlikely compared to absorption.
1% for CO2 stopping ” dead”
0.25% for CO2 to be left with average KE
Conclusion;
either I’m making a mistake or CO2 in this situation seems to be cooling the surface
See Roy Spencer: Why 33 deg. C for the Earth’s Greenhouse Effect is Misleading September 13th, 2010
But what many people don’t realize is that the 33 deg. C of surface warming is not actually a measure of the greenhouse warming – it represents the balance between TWO competing effects: a greenhouse warming effect of about 60 deg. C (the so-called “pure radiative equilibrium” case), and a convective cooling effect of about 30 deg. C. When these two are combined, we get the real-world observed “radiative-convective equilibrium” case.
David from Roy Spencer
…..”The value of 33 deg. C represents the difference between the observed average surface temperature of the Earth, and the estimated surface temperature if there was no atmosphere.”…..
This is a fairly artificial construct.
What about the storage capacity of the Oceans?
What about an atmosphere without CO2 and H2O radiating in the IR.
To come up with the worst case scenario- a bare rock Earth and then speculate that without IR active CO2 and H2O average Earth surface temperatures would be around 255K is claiming to much for the so called “greenhouse effect”.
What are you trying to say?
Ocean storage has very little impact on average temperature.
(only day-day – season-season averaging etc.)
No CO2 & H2O – no IR absorption / radiation
= no conventional planetary “greenhouse”.
These “what ifs” are a bit artificial.
A more instructive comparison to test the true extent of the Greenhouse Effect would be;
1. Bare rock Earth temperature 255K .
2. Earth with Oceans and Atmosphere butwith no IR radiative gases.
I would guess that 2 would be pretty close to our own climate a bit warmer by day and colder by night.
But nothing like the difference of 33c claimed for the Greenhouse Effect.
The post may be misinterpreted the CO2 and H2O would be there but not IR active.
If we want to convince people of the reality of the greenhouse effect, we should first stop calling it the greenhouse effect – I guess this is the reason for the “?” in the title of the thread. I assume we are all agreed that the “greenhouse effect” is not what keeps greenhouses warm? Although there is much nonsense in the G&T paper, they are correct about this – largely by quoting extensively the experiments of Wood (1909). Greenhouses work by preventing the hot air rising. There are other obvious simple experiments to confirm this – eg open a roof window a bit and most of the heat is lost, which wouldn’t happen if absorption and re-emission of radiation was the main process.
This highlights a major flaw of climate science – it seems to only consider radiative heat transfer and neglect heat transfer by convection.
I agree, the word greenhouse is a misnomer, but I suspect we are stuck with the terminology.
Irreversibly stuck … something about hoists and petards, I think
I think that is too bad. It is difficult to sell the idea that something is an egg, when in fact it is not.
Frankly I think as people get more and more frustrated with a science community that is obsessed with what is in effect marketing, the drift of names, from global warming to global climate change to global climate disruption added ot the idea that what we are told is the fundamental driving mechanism is in fact not at all properly named to the point of being misleading, is not going to do the climate science community any good at all.
Add to that the string of dubious claims and failed predictions, and you have yourselves painted into a corner.
PaulM
R W Wood showed that;
1. A glasshouse only worked by stopping convection.
2. The remaining real residual radiative effect was so small that it could be almost ignored.
Its this second part that most people seem to miss.
Here is a paper that more people should read.
Especially as it comes from a source with no “spin” on the AGW debate.
The way I read the paper is it gives massive support for the conclusions of the famous Woods experiment.
Basically the project was to find if it made any sense to add Infra Red absorbers to polyethylene plastic for use in agricultural plastic greenhouses.
Polyethylene is IR transparent like the Rocksalt used in Woods Experiment.
The addition of IR absorbers to the plastic made it equivalent to “glass”
The results of the study show that( Page2 )
…”IR blocking films may occasionally raise night temperatures” (by less than 1.5C) “the trend does not seem to be consistent over time”
Thus inside a large real greenhouse where all the IR is trapped it made little or no difference to the temperature.
Its this kind of simple bulk effect that makes sceptics convinced that the greenhouse effect is so small that it cant be responsible for the claimed 33C increase in atmospheric temperature
Bryan, do you have a citation or even better a link to this paper?
David Wojick
Sorry all I forgot to post the link.
http://www.hort.cornell.edu/hightunnel/about/research/general/penn_state_plastic_study.pdf
I may comment more later since I only skimmed the short paper.
First, did you notice this comment in the results section: “but again the unreplicated nature of that comparison make firm conclusions difficult to make.”
Second, an important part of blocking radiation is the thickness of the material. That paper is unclear about these values (though I suppose I could research the Dupont materials used). If you have something very thin, adding an even thinner coat of anything may not do much. Common glass is much thicker than Seran wrap, for example. If we have significant thinness, then getting any extra heating suggests there may be something very significant there (contrary to what you are suggesting). Note, that our atmosphere is very thick, allowing IR to be absorbed not just over microns, but repeatedly over miles.
Third, a professor Pratt performed a recent experiment that strongly suggests a greenhouse effect. One point he noticed is that it takes extra time for extra warmth of many degrees C (rise in temp in his experiment setup) to accumulate under various covering scenarios (with some being better greenhouses than others). Waiting an hour, I think, was not sufficient to differentiate the different qualities of coverings, with the better material actually going a little slower in heating up to its final significantly higher temp. In the case of the current experiment, they were interested simply in slowing down heat loss, not in seeing how hot it can get, and they appear to have covered the vegetables in the evening after most of the sunlight strength was already diminished. [Again, they give few experimental details — just like the meager details given by Woods.]
In short, the authors don’t claim any firm conclusion, and the paper lacks much detail and doesn’t explore the problem too seriously (they state this). They certainly make no claims that greenhouse effect is negligible (as you appear to want to suggest from their paper) or that our thick earth atmosphere somehow doesn’t improve the heat retention ability of the environment during the night when all we have out there is super cold space with almost no direct radiation.
Judy – Let me put a plug in for Raymond Pierrehumbert’s forthcoming opus, “Principles of Planetary Climate” (Univ. Chicago), due out in January (I have a draft copy). Like some of your other references, it addresses radiative transfer and greenhouse effect mechanisms in quantitative detail, but also deals with many other climate-related topics. Unlike what seems to be the focus of some of the texts you’ve listed, this one addresses the effects of greenhouse gases not only from the perspective of radiative transfer, but also with a discussion of radiative/convective equilibrium as well as other processes relevant at various levels – surface, boundary layer, free troposphere, stratosphere, etc. I believe that anyone who makes the (sometimes arduous) effort to read through the book will come away with a good understanding of the greenhouse effect as well as the role of specific molecular species (CO2, methane, water, etc.) in mediating the effect.
Does it attempt to quantify the effects of clounds and ocean currents?
I am prepared to believe that Pierrehumbert’s book should be quite good, i look forward to it.
Perhaps things might be easier to discuss if we simply dump the term ‘Back Radiation.’ Scattering would probably be a better term. Scattering is something we see with our own eyes quite often. That glow we see along the beam of our automobile headlights is due to scattering of light. That glow along the beam of other automobiles is also visible and even provides a little illumination of objects at the side of the road. While not being particularly helpful for driving at night, it does provide an example scattering we can all relate to.
Next, can we also dispense with the idea that cooler things cannot add heat to warmer things. All things, including atmospheric gasses radiate photons at wavelength’s and quantities determined by the object’s absolute temperature. Photon’s are not particularly smart. They really have no clue whether they are heading toward a hot or cold place. Whatever absorbs them will receive their energy.
Whatever happens after a photon is absorbed is determined by the specific materials characteristics. It may simply get warmer. It may quickly re-radiate a new photon of the same wavelength in either the direction the original photon was traveling or some other direction (scattered). It may re-radiate a photon of lower energy level and keep some of the energy as heat.
Those two fairly simple concepts allow us to conclude that thermal radiation from atmospheric gasses, or at least part of it, can occur in the direction of the ground and will have a heating effect. The issue should not be whether those effects exist but what their total quantitative impact is.
Does that satisfy non technical folks without violating any scientific principles in describing a ‘green house’ effect? (By the way, I am one of those folks labeled as a skeptic.)
No, it isn’t scattering. It is thermal emission of IR.
Point taken. I do suppose we can say that convection can move heated air upward which can raise the energy level of CO2 molecules to occasionally reach a state where they release a photon to return to a lower energy state. Also, I suppose absorption of an infrared photon could result in a simple kinetic energy increase which gets transferred to nearby gas molecules. Then again, the CO2 molecule could just remain at that higher energy level for a while and then shoot a photon out at a later time. All are fun reactions to contemplate. I’m curious what the higher probability thermal activity of CO2 molecules is at high altitudes.
Gary,
‘Then again, the CO2 molecule could just remain at that higher energy level for a while and then shoot a photon out at a later time.’
That is the dominant process that leads to the greenhouse effect.
A CO2 molecule absorbs an IR photon giving off by the thermally excited surface of the earth (earthlight). The energy in that photon gets redistributed by non-radiative relaxation processes (collisions with other molecules mostly) and then emits a lower energy IR photon in a random direction. A collection of excited CO2 molecules will act like a point source, emitted IR radiation in all directions. Some of that light is directed back at the surface of the earth where it is absorbed and the whole thing happens over again.
All of this is very well understood, though in the context of the CO2 laser. If you’re interested in these dynamics, there is a great literature on the relaxation processes (radiative and otherwise) that occur in an atmosphere-like gas.
Maxell:
That sounds correct to me. I guess it was a little simplistic to label it scattering. I was shooting for a non-technical image and took a liberty with terminology.
Gary,
I don’t think it’s simplistic to label it scattering. Inelastic light scattering does occur in the atmosphere from CO2 molecules. It’s known as Raman scattering in fact.
It’s just that the probability of a scattering event is much, much smaller than the probability of an absorption and then subsequent emission. So I think that’s why some took note of your using the word ‘scattering’ in this context. Because that word is used to denote an entirely different physical process.
Keep thinking though. We need it.
Dr. Curry, I have no scientific dog in this fight so I watch it merely as an issue analyst. I am struck by the fact that you first say greenhouse skepticism is erroneous and not plausible, then add “I don’t have a full understanding of what the actual issues are with the greenhouse effect skeptics.”
This reminds me of Thomas Reid’s famous response to Hume regarding the problem of induction. Reid is said to have said something like “If a man goeth down a road and by and by he falleth into a coal pit, it taketh no great wit to see that he hath made a wrong turn.” There is of course no rebuttal in this colorful response. “You must be wrong” is not an argument.
Thus it might be that in addition to a deeper understanding of the greenhouse effect it might be of some use if we actually understood the skeptics. Just a thought.
For example, so far as I can tell one basic problem is that in addition to radiative transfer there is a lot more going on in the atmosphere. Perhaps we are lacking a good account of the mechanism (as you suggest) just because that mechanism is both complex and ill defined. Then too there is this puzzling “talking past” in which the different sides do not seem to be responding to specific points made by the other. As Kuhn pointed out this problem is often a symptom of deep conceptual and theoretical differences.
Taken together these two problems may help explain the complex confusion that seems to pervade this issue of the greenhouse effect.
When somebody says the greenhouse effect doesn’t exist, i do not regard this as plausible. I have not delved deeply into the arguments made by Miskolczi and others, but on the surface they make no sense.
“I have not delved deeply into the arguments made by Miskolczi and others, but on the surface they make no sense.”
Please take a look at the thread on my blog. There are a couple of links to non-technical summaries which may help with orientation on the technical paper.
http://tallbloke.wordpress.com/2010/01/04/why-the-sun-is-so-important-to-climate/
The Miskolczi makes sense to me and I barely understand this stuff. His is an argument from observation, not from theory. I am not saying he is right just that his is a real scientific argument, the kind that one has to delve deeply into. In fact I know of no serious scientific issue that can be resolved without delving. Science is hard. Perhaps you should just say you are skeptical, not that they can’t be right, given that you have not done the work.
“His is an argument from observation, not from theory”
This is an argument that Miskolczi supporters resort to when the flaws in the theory become too obvious. But it just isn’t true. M used a whole lot of radiosonde data from a database. But it doesn’t include any radiative measurements, or other data that would substantiate his theory. It’s just pressure and gas concentrations, which he then feeds into his computer program for radiation modelling. The “observations” in no way validate his claims.
Nick, as Nullias in Verba points out below, the noddy greenhouse explained by most physicists is for an Earth with no convection in it’s atmosphere. Miskolczi uses gas pressure, adiabatic lapse, and concentrations because these are what matter over most of the atmospheric column. You guys really need to get a handle on the relative scale of effects.
Miskolczi refers to no convection data in his 2010 paper, and it doesn’t seem to appear in his theory. His calculations seem to be entirely radiative, based on his LBL program.
You just said:
“M used a whole lot of radiosonde data from a database. But it doesn’t include any radiative measurements, or other data that would substantiate his theory”
Now you say:
“His calculations seem to be entirely radiative, based on his LBL program.”
So which is it?
If you are going to say he isn’t using empirical radiative measurements, I’m sure you’ll find he is in good company…
Exactly as stated. He has no radiative measurements – his main activity is doing radiative calculations using Hartcode. This needs as input data gas concentrations and pressures, which he gets from the radiosonde database.
He’s not the only person doing theoretical work with models of radiative transfer and empirical data is he? Why do you think this constitutes a fatal criticism? It’s good that a variety of different approaches are used, utilising those longer term datasets we have, even if they are not perfect.
What he has discovered is that there has been a balancing out of effects from co2 and water vapour, and this leaves the field open for other causes of warming. i.e. the empirically measured decrease in tropical cloud cover 1980-1998 which no warmist ever wants to discuss. I calculated that this led to a 4W/m^2 forcing on the surface in the 1993-2003 decade. That was mostly the sun’s energy, not increased back radiation Nick.
There are two textbooks I can think of offhand that give very good accounts of what happens when you enhance the greenhouse effect. Houghton’s ‘Physics of Atmospheres,’ and the best description I’ve seen is not yet available to the public, but within a month or so look for Ray Pierrehumbert’s upcoming text on ‘Principles of Planetary Climate.’ These texts both involve math and physics a bit beyond the typical blogosphere article, but it’s not so technical as, say, Goody and Yung and so I think they are accessible to an educated audience. Pierrehumbert, in particular, makes you think of the greenhouse effect in the context of other atmospheres as well, such as on Mars/Venus, during snowball Earths, and he delves into the runaway greenhouse issue.
Another great book is Grant Petty’s ‘Introduction to Atmospheric Radiation.’ If you’re interested in all the molecular-stuff at a respectable but not overwhelming level of technical detail, this is a must-read (definitely know algebra, just a bit of calculus and physics). It’s probably the best radiation book for an audience making the transition from a few calculus and physics courses to their first atmospheric science exposure. Petty is a satellite expert and so he focuses a lot on spectra from space and you’ll be very good at interpreting them after reading the book, but he doesn’t actually complete the connection to the greenhouse effect, although he could have easily connected the dots to one of the better ways of describing how it actually works.
Any review of these texts will allow the reader to dissect the problems in G&T, Miskolczi, or ‘slaying the dragon’ type reads. None of them even provide respectable objections to the current physics, they are just ridiculous. Some people will say they reflect poor understanding, but IMO they are so bad in their understanding that they reflect an intent to mislead. Our paper, Halpern et al (2010), was a bit off in that wingnut theories typically won’t get the detailed ‘rebuttal’ that we provided, but we (or at least I) felt it was necessary only because of the importance of the topic to the non-scientific audience, but I was unaware of how this article was allowed to get into IJMPB. It only shows if you are persistent enough you can publish anything, especially in obscure journals (like Miskolczi’s original piece in a odd Hungarian journal or E&E)
Part of the issue with the whole ‘blanket analogy’ is that it tells you the greenhouse primarily impacts the “energy out” side of the budget rather the “energy in” part, but that’s it– it doesn’t actually tell you how this works. It doesn’t allow you to appreciate the importance of the thermal structure of the atmosphere, the spectral selectivity in absorption, etc. All of these things can be learned without understanding Partial Differential equations and other sorts of crazy math, but allow you to actually understand what’s going on and connect it to other situations.
Depending on the level you are looking for, I would also again recommend chapters 2-5 of David Archer’s “Understanding the Forecast” (2. Blackbody radiation, 3. The layer model, 4. Greenhouse gases, 5. The temperature structure of the atmosphere), which comes with video lectures and online models related to learning assignments in the text.
This is taught at the first year university level, but does not require much prior work in physics or chem. He also does a pretty good job of discussing the physics at the molecular level, as I recall.
I agree…this is a good introduction to the molecular stuff too that Judith has been talking about as well.
Chris, since the net longwave gives a cooling of ~70W/m^2, mostly due to the concentration of back radiation on the sea surface causing evaporation, please could you explain why more back radiation wouldn’t lead to more evaporation.
Thanks.
As a simple lay-person, I like to keep things simple. Of course, in the ‘climate debate’ hardly anything is simple but try this for size…
As a skeptic (or at least one who is developing that view!), I certainly do not ‘deny’ that the greenhouse gasses have a property which can lead to, er… a warming effect commonly known as ‘greenhouse’. (How anyone got away with coining that term just shows how science can be corrupted by soundbites.)
Anyway, it is the scale of the warming effect of ghgs that most skeptics can’t accept. Please correct me if I’m wrong in that assertion.
All the greenhouse gasses put together amount to 0.04% of the dry atmosphere. This means that 99.96% (Nitrogen, Oxygen and Argon) CANNOT be ‘heated’ by radiation (because radiation is not heat per se) and therefore must be warmed by conduction.
If you add H2O to the mix (I will use an average of 2%), you effectively have, out of a total of 102%, 2.04% being able to absorb radiation, 0.04% being able to re-emit radiation and 99.96% which can only be warmed by conduction. (I discount convection because, in reality, convection merely re-distributes any heat.)
The (C)AGW theory appears to be based on a belief that an increase in the 0.04% (actually 0.028% back in 1850) is likely to cause a significant, nay, catastrophic rise in global temperatures.
A debate on the core physical processes of the Greenhouse Effect is probably long overdue.
Please add to your list of papers those by OG Sorokhtin, GV Chilingar et al:
http://docs.google.com/fileview?id=0B74u5vgGLaWoYTAyYTc4NmUtZDFkMC00ODg3LTgwYzAtOTg3OTJhZjI5MDVk&authkey=CKyD1r8H&hl=en
http://www.climatephysics.com/PDFs/Chilingar%20-%20Cooling%20due%20to%20CO2.pdf
neither link turns up anything?
2nd try full paper (works for me):
https://docs.google.com/fileview?id=0B74u5vgGLaWoYTAyYTc4NmUtZDFkMC00ODg3LTgwYzAtOTg3OTJhZjI5MDVk&authkey=CKyD1r8H&hl=en&pli=1
abstract:
http://www.springerlink.com/content/c47m4x8222886n12/
the full paper on the 2nd reference was apparently taken down, but abstract is here:
http://www.informaworld.com/smpp/content~content=a788582859~db=al
So what have we been doing wrong in terms of explaining this…
It is what you suspect; your target audience has not been targeted. Most information is directed at either school children or climate scientists.
Here is the skeleton of a simple Newtonian approach, no need to start off with radiative heat transfer and atmospheric physics:
1. The rate of incoming heat and outgoing heat at the Earth’s surface is convergent.
2. The rate of heat flow between two bodies is proportional to the difference in temperatures.
3. The direction of heat flow is from the higher temperature body to the cooler. (Sun to earth, earth to space)
4. If (perhaps a big if) we can choose one body as the surface of the earth, and the second body as a spherical shell consisting of the atmosphere at a given height from the surface, then:
5. Any increase in temperature in the atmospheric body will decrease the rate of heat transfer from the surface.
6. The resultant increased surface heat will cause surface temperatures to increase until the out-going rate of heat flow converges to the incoming rate.
What remains is making the case for atmospheric temp increase (#5) and quantifying the magnitude of the effect.
Too simplistic for physicists, yes. But not necessarily unacceptable to the intended audience.
To put some sinew on the skeleton, if the shells are arbitrarily thin, then the higher order terms of the Stefan-Boltzmann equation drop out. Radiative heat transfer becomes proportional to the difference in temperature – similar to convective cooling in a Newtonian ‘body’. Also, arbitrarily thin shells could represent both a Newtonian ‘body’ and an S-B surface. We end up with different constants for convective and radiative heat transfer and a model analogous to an electric parallel circuit.
This seems intuitively sensible, qualitatively correct and all we need are 1st order differential equations to make it work.
Isn’t this better than a greenhouse model?
Of the several problems I see with this approach, the biggest is that it only works when looking at heat transfer between adjacent temperature shells. Otherwise the errors caused by dropping the higher order S-B terms accumulate.
Here is an item I wrote up to try and crunch the whole GHG idea into a paragraph.
The Greenhouse Effect 101 . To balance incoming short-wave solar energy, the earth constantly radiates long-wave heat energy (infrared photons) back out to space. This is how the earth maintains a fairly constant temperature. Some of the outgoing radiation is absorbed & re-radiated back to earth by various trace gases like carbon dioxide, water vapor, methane, & ozone. This gives us the greenhouse effect, & keeps the earth from becoming a ball of ice. The warming effect works according to the laws of quantum physics. When an infrared heat photon of a specific energy collides with a greenhouse gas molecule, that photon will be absorbed & an excited electron will jump to a higher orbit. However, that new electron orbit is not stable & will soon fall back to its “rest” energy level, & emit a photon of the same energy level (frequency) that was absorbed. While the original photons were on their way out to space when they were absorbed, the new photons will be radiated in a random direction. Some will continue up, some will return toward earth. It is this back-to-earth radiant energy that causes the underlying earth to warm to a new equilibrium temperature. Because of its complexity, only computer models can adequately quantify the greenhouse effect. The exact magnitude of this effect caused by gases humans are adding to the air is not yet precisely understood, but all models to date have shown various amounts of warming. None show the earth cooling or remaining the same.
I am Dr Curry’s assumed audience – I took the right courses, plus a few more in grad school, but I am not prepared to do a degree in physics or climate science. As a luke-warmer, I’d like to make a distinction: Not all ‘deniers’ deny the existence of a greenhouse effect. I’ll grant a greenhouse effect to CO2, to what ever degree the relevant scientific community assign it.
What I’m skeptical of, however, is the degree to which adding CO2 to the atmosphere affects planetary heat content and temperatures. We’re not dealing with a sealed flask of gases on a lab bench here. While I do not know the physics of the various and sundry forcings and constraints of planetary temperatures, I do know that in spite of the fact that CO2 levels have gone up and down over billions of years, there has never been a thermal runaway that burned the water off the planet. Why not?
Obviously, there is some kind of thermostat operating – and operating against the effects of greenhouse gases. If Hansen’s tipping point exists now – at the end of Obama’s first term – then why hasn’t it existed in the past? This is where my skepticism is located – not in the existence of the greenhouse effect – which is well-demonstrated – but in the chaotic mix of causes that sum together to give us our planetary climate. I don’t need convincing on the greenhouse effect – I need convincing on the application of the greenhouse effect to measured decadal predictions of planetary climate.
Another very simple analog is a layer of heat insulation. Of course diffusion of heat in an insulating layer is in many ways different from the psysics of radiative transfer of energy in the atmosphere, but the basic idea is rather similar.
When the incoming flux of energy is kept the same, better insulator leads to a higher temperature at the source. In the equilibrium the outgoing heat flux equals the incoming flux, but the temperature gradient is higher to compensate for the reduced conductivity of heat.
Simple, yet false analogs are not what we need. As Dr. Curry indicated in her initial post, the debate is over detailed mechanisms.
Perhaps I should expand a little on the analogy.
In the diffusion of heat the macroscopic diffusion equation is very simple, but on the molecular level the situation is much more complicated. On the molecular level, energy is transmitted in all directions exactly as absorption and emission proceed in all directions. If absorption is strong at all wavelengths the radiative energy transmission proceeds very closely as heat conduction in solid insulator. The principal difference comes from those wavelengths where radiation can get through a large fraction of the atmosphere and even the whole atmosphere without being absorbed. Convection adds to the differences, but even so the dominant effect is very similar.
I think it is very much debatable whether this is a false analog. Certainly it is not complete, but is it really false?
A great deal of confusion is caused in this debate by the fact that there are two distinct explanations for the greenhouse effect: one based on that developed by Fourier, Tyndall, etc. which works for purely radiative atmospheres (i.e. no convection), and the radiative-convective explanation developed by Manabe and Wetherald around the 1970s, I think. (It may be earlier, but I don’t know of any other references.)
Climate scientists do know how the basic greenhouse physics works, and they model it using the Manabe and Wetherald approach. But almost universally, when they try to explain it, they all use the purely radiative approach, which is incorrect, misleading, contrary to observation, and results in a variety of inconsistencies when people try to plug real atmospheric physics into a bad model. It is actually internally consistent, and it would happen like that if convection could somehow be prevented, but it isn’t how the real atmosphere works.
This leads to a tremendous amount of wasted effort and confusion. The G&T paper in particular got led down the garden path by picking up several ‘popular’ explanations of the greenhouse effect and pursuing them ad absurdam. A tremendous amount of debate is expended on questions of the second law of thermodynamics, and whether back radiation from a cold sky can warm the surface. It can, but whether it can or not is actually completely irrelevant to the real greenhouse effect. It doesn’t matter, because back radiation isn’t what causes the surface to be as warm as it is anyway.
The greenhouse effect requires the understanding of two effects: first, the temperature of a heated object in a vacuum, and second, the adiabatic lapse rate in a convective atmosphere.
For the first, you need to know that the hotter the surface of an object is, the faster it radiates heat. This acts as a sort of feedback control, so that if the temperature falls below the equilibrium level it radiates less heat than it absorbs and hence heats up, and if the temperature rises above the equilibrium it radiates more heat than it is absorbing and hence cools down. The average radiative temperature for the Earth is easily calculated to be about -20 C, which is close enough although a proper calculation taking non-uniformities into account would be more complicated.
However, the critical point of the above is the question of what “surface” we are talking about. The surface that radiates heat to space is not the solid surface of the Earth. If you could see in infra-red, the atmosphere would be a fuzzy opaque mist, and the surface you could see would actually be high up in the atmosphere. It is this surface that approaches the equilibrium temperature by radiation to space. Emission occurs from all altitudes from the ground up to about 10 km, but the average is at about 5 km.
The second thing you need to know doesn’t involve radiation or greenhouse gases at all. It is a simply physical property of gases, that if you compress them they get hot, and if you allow them to expand they cool down. As air rises in the atmosphere due to convection the pressure drops and hence so does its temperature. As it descends again it is compressed and its temperature rises. The temperature changes are not due to the flow of heat in to or out of the air; they are due to the conversion of potential energy as air rises and falls in a gravitational field.
This sets up a constant temperature gradient in the atmosphere. The surface is at about 15 C on average, and as you climb the temperature drops at a constant rate until you reach the top of the troposphere where it has dropped to a chilly -54 C. Anyone who flies planes will know this as the standard atmosphere.
Basic properties of gases would mean that dry air would change temperature by about 10 C/km change in altitude. This is modified somewhat by the latent heat of water vapour, which reduces it to about 6 C/km.
And if you multiply 6 C/km by 5 km between the layer at equilibrium temperature and the surface, you get the 30 C greenhouse effect.
It really is that simple, and this really is what the peer-reviewed technical literature actually uses for calculation. (See for example Soden and Held 2000, the discussion just below figure 1.) It’s just that when it comes to explaining what’s going on, this other version with back radiation getting “trapped” gets dragged out again and set up in its place.
If an increase in back radiation tried to exceed this temperature gradient near the surface, convection would simply increase until the constant gradient was achieved again. Back radiation exists, and is very large compared to other heat flows, but it does not control the surface temperature.
Increasing CO2 in the atmosphere makes the fuzzy layer thicker, increases the altitude of the emitting layer, and hence its distance from the ground. The surface temperature is controlled by this height and the gradient, and the gradient (called the adiabatic lapse rate) is affected only by humidity.
I should mention for completeness that there are a couple of complications. One is that if convection stops, as happens on windless nights, and during the polar winters, you can get a temperature inversion and the back radiation can once again become important. The other is that the above calculation uses averages as being representative, and that’s not valid when the physics is non-linear. The heat input varies by latitude and time of day. The water vapour content varies widely. There are clouds. There are great convection cycles in air and ocean that carry heat horizontally. I don’t claim this to be the entire story. But it’s a better place to start from.
Of course, given the number of competing claims and assertions in this area, all this just looks to most participants like another crank version and gets ignored, even by sceptics. I am not hopeful. It would require more ‘official’ climate scientists to stop using their simplistic version and be a bit more careful, and would take a while to percolate into the public consciousness. Probably they don’t because they know what people would say.
My apologies for the length of this comment.
(This was supposed to be a reply so I am reposting it as one, to maintain continuity.) Very nice, Nullius (may I call you Nullius?). This at least gives the flavor of the complexities, and helps explain the confusion that is obvious wherever this topic arises. I am particularly interested in the idea that some calculations “use averages as being representative, and that’s not valid when the physics is non-linear.” The challenge of non-linearity pervades climate science, so it is not surprising to find it here too.
While this is one way of looking at the effect and while this may well be the way atmosphere is analyzed, this does not explain the effect. The basic physical process that leads to warming is the absorption and emission of radiation. Any explanation must start from that fact.
You stated that purely radiative calculations are self-consistent. They give also quite reasonable results. A simplified atmosphere with convection is likely to lead essentially to the same result. This is hardly a coincidence. I think that there is more truth in the purely radiative calculation than you indicate. It is just another way of looking at the same effect. It has the great advantage that it is based more directly on the basic physical effect.
(I am not an atmospheric scientist, but I am a physicist. These comments are largely based on my intuition as a physicist.)
Again I continue my argument.
My understanding is that convection is not essential for understanding the greenhouse effect. The lapse rate is determined by the stability condition of the atmosphere. If the lapse rate would not be correct strong instabilities would be created, but when it is correct they are not essential for explaining the effect. Therefore it is correct to explain the greenhouse effect looking only at the radiative energy transfer. Minor corrections are needed for precise results but not for explaining the effect.
No, convection is not a ‘minor correction’ and a convective atmosphere has a completely different temperature profile and heat flux balance from a purely radiative one. The purely radiative argument – as described repeatedly by climate scientists – is simply not what happens in the Earth’s atmosphere.
I was not clear enough on what I ment. My idea was that the temperature profile remains essentially the same and changes in the profile are “the minor correction”.
Perhaps my later posts (from Dec 1) lower in this chain explain better, what I have in mind.
It’s not quite that straightforward, it is like asking why the temperature of a pan of boiling water on the stove is 100 C. The answer given is that it is because the gas is set to 2, which liberates so many Watts of heat, which enter the bottom of the pan and increase its temperature. So if I turn up the gas to 4, will the temperature of the water increase to 200 C?
Instead, what I am saying is that the reason the temperature of water is 100 C is that it is the boiling point of water, and that more heat only increases convection, which carries the heat away faster.
As an explanation for why the water is hot, the gas is a good starting point. As an explanation for why the temperature is 100 C, the gas argument misses the point entirely. It doesn’t control the temperature.
The radiative calculation gives the wrong result. The temperature profile of the atmosphere would be exponential, not linear, and the average surface temperature would be around 60 C (IIRC). Both are contradicted by the evidence. The controlling mechanism is not back radiation.
I am not sure, whether you read my later message.
It is clear that one cannot explain the temperature profile of the atmosphere or even the change in the temperature profile by radiation only.
Still one may be able to explain the warming of the earth surface through the analysis of the radiative processes with a minor complementary addition from the stability condition.
(Here I naturally consider only the basic effect forgetting many types of feedback.)
Yes, this is exactly what the climate scientists do. They explain only the pure radiative process, and then describe convection as a “minor correction”. Except that from the point of view of the dynamics, it isn’t minor – it actually dominates the effect.
With convection, the basic mechanism is as above, and the radiation is a minor correction. (It just reduces the amount of convection necessary to maintain the adiabatic lapse rate).
You don’t actually need to involve radiation internal to the atmosphere, and given all the fuss and argument and scepticism it raises, it’s positively counter-productive to use the radiation argument. So why use it?
Why use the radiation?
Because CO2 affects the radiation and (in practice) only the radiation.
“Because CO2 affects the radiation and (in practice) only the radiation.”
Yes. But that’s already incorporated into my model. More CO2, being opaque to longwave IR, increases the thickness of the “fuzzy layer” and hence the average altitude of emission to space. The relevant radiative property of CO2 is indeed included. Irrelevant and distracting properties are ignored.
When I say “the radiation argument” I mean the pure radiation, non-convective argument.
In any case the whole effect of CO2 is radiative. That is the only direct effect. Everything else is adaptation to the changes that this basic effect creates.
If one wishes to convince scientists with sufficient background to understand the explanations, one must base the whole argument on this. Whatever else is needed about the atmospheric physics, is addtional.
In a stationary situation the net energy flux through any surface is zero. This fact guarantees that there are many different equally correct ways of describing the same effect. The question is, which of these ways is easiest to explain to educated people who are not atmospheric scientists.
Please, I’m not saying that the direct effect of CO2 is not radiative. But just because the first step in the chain is radiative, you can’t then say that all the rest of the chain of effects in the mechanism are purely radiative too.
If you want to convince scientists with sufficient background to understand, you have to use the correct mechanism. If you use the wrong mechanism, and then some sceptic comes along and points out the flaws and contradictions in it, they’ll become sceptical too. They’ll start asking why they’ve been fed this line of hooey for all these years, and why none of their climatology colleagues said anything.
I should know.
As I stated below, if I understand the argument you two are having: Pekka is saying that increasing the thermal resistance for a given heat flux will require higher temperatures and that analogously explains the greenhouse effect. Nullius is saying that the additional piece that is missing without taking into account the physics behind the nearly constant lapse rate is that the resistance increase comes from a thicker layer, not from a change in the insulator’s conductivity.
May I ask, if more CO2 increases the thickness of the “fuzzy layer”, does it actually increase temperature at say 1mtr height?
I believe the answer should be yes – because the radiating height is at 255K and if that point moves higher, it increases temperatures of all points between that height and earth’s surface.
Yes, it turns out CO2 will warm all layers of the atmosphere below the tropopause
Hi Chris, my question is: has it warmed all levels of the atmosphere below the tropopause? I’m only asking because I don’t know and I was just wondering if measurements had confirmed this.
And the predicted hotspot?
For data, see figure 1 here. The answer is that the measured trends are almost all positive, but I think that the error bars are such that this probably cannot be relied upon above 2 km.
The tropical hotspot is not a consequence of greenhouse gases, but of water vapour changing the lapse rate. The theory of water vapour feedback says that warming from CO2 alone should increase the amount of water vapour in the atmosphere, which reduces the lapse rate (the rate at which temperature falls with altitude). The temperature at the 5 km emission level acts like the pivot on a see-saw. The temperature there rises due to CO2, the temperature below it rises but not as much, due to the see-saw levelling out, and the temperature above it rises even faster than CO2 alone requires.
The absence of a hotspot is evidence that the feedbacks are probably smaller than the climate models suggest. It doesn’t say much one way or the other about whether GHGs are responsible for the late 20th century rise.
The hot spot is another reason why a proper understanding of the greenhouse effect requires discussion of lapse rates, not just radiation.
For a recent discussion of the hotspot, see this
Perhaps hunter has already read it.
And the follow up here, of course. Although that one does get rather technical and doesn’t present the data by altitude as clearly.
Pat – That is an exceptionally detailed and informative analysis of the tropospheric amplification (“hotspot”) issue. What emerges is that the main problem in accurate assessment is probably not statistics but instrumentation bias due to instrument changes over time. The most direct measurements (but also most vulnerable to instrumentation errors) come from radiosondes. All other sources are indirect, and tend to disagree with each other. Tropospheric amplification has been well documented over short intervals but remains problematic over longer ones, altough this discrepancy lends itself better to a measurement trend bias problem than a physical explanation.
The “hotspot” is not specific to GHG-driven warming, but is an expected feature of surface warming from any cause, and does not originate in climate models but in the basic equations of climate physics, including the quasi-exponential Clausius-Clapeyron equation. It is not a reflection of feedbacks in general, but of a particular negative feedback, the lapse-rate feedback. In that sense, one could argue that if the discrepancies are real, negative feedback is weaker (and hence positive feedbacks more dominant) than is ordinarily estimated. I don’t consider that argument to be plausible, because I expect the eventual resolution of the issue will reside in improved methods for quantifying long term trends. It is also possible that a true physical process underlies a small part of the discrepancy, but since the evolution of instrumentation has progressively reduced the discrepancy over time, measurement issues probably dominate. Interestingly, although some indirect measurement techniques (e.g., MSU data) still show some distance between recorded and predicted data, other techniques show none – including thermal wind equation methods and recent observations on SST warming-related changes in convective theshhold.
Excellent summary, thank you. These complexities of the convective sitution is a lot of the reason for my scepticism about the ability of the current models to give worthwhile results. It is also the reason why I take any sensitivity calculation with a big dose of salt. The Earth’s climate system is a heat engine, and if some variable like the latitudinal position of the jet streams alters a small amount, the effect will make a 30% change in the level of co2 causing a 1.7W/m^2 forcing seem pretty tiny in comparison.
Tallbloke,
The discussions by Nullius, which are basically the same as mine, tell why there is an atmospheric greenhouse effect. They do not tell anything about feedback, which is the real issue of the big debate. The main issue of feedback is whether it is large positive, small positive or negative. The result is that a doubling of CO2 may cause several degrees C per doubling, or a fraction of a degree C per doubling. I think it is a fraction of a degree C. I don’t know what Nullius thinks.
Leonard, we might listen if the ‘counter-arguments’ were not ones from ignorance, straw man attacks ,or other such fallacious lines of thought.
Chris,
Please give examples of what you are talking about. If it is my opinion on the amount of feedback, this is the opinion of Roy Spencer and others, and agrees with actual heating rates measured, without having to balance two large effects (heating from CO2 plus feedback with aerosols) to get a small result. If it my analysis of how the atmospheric greenhouse works, I will elaborate as much as you wish. You attack my statements with no support at all.
Based on your history elsewhere of what you post, I find no use in discussing this with you.
Chris,
Sounds like you are afraid to discuss facts. I had a nice discussion with scienceofdoom, and I think he is closer to my position on this model now. I am presently debating Tom Curtis on climate clash (on more general issues) and he seems to be a very smart person. What is your problem?
This is what always happens when we get close to the heart of the issue. Closing of ranks, and minds. Aerosol feedbacks are a figleaf to cover a failed theory. Some aerosols warm, some cool. There is no tropospheric hotspot , which would have to be there for the atmosphere to be responsible for ocean temperature increase, and instead it’s the ocean which drives the atmospheric temperature. This is easily demonstrated by observing the lag between ocean temp change and the following atmospheric response.
It’s the Sun heating the ocean through lowered tropical cloud albedo 1980-1998 which caused the warming. The empirical data tells us this, but some people just pull their blinkers a bit tighter when confronted by the fact.
“Aerosol feedbacks are a figleaf ”
Someone here, I forget who, introduced me to the term “theory-saving” to describe this kind of argument, and I rather like it. In strict terms, I suppose it’s “counter-parsimonious” :-)
Chris,
Inevitably at this point, on other blogs, someone would be posting links to the Song of Sir Robin to highlight your choice.
Nullius,
You got it exactly right. This is what I keep telling Chris and others, but you told it more clearly, so they may pay more attention.
I think another way to look at it analogously is that when you have a constant current flow (radiated heat) at steady state through a resistive material (atmosphere) with a certain resistance per unit length (equivalently related to the lapse rate), adding more CO2 is equivalent to making the resistor longer resulting in a higher potential difference (equivalently temperature difference between earth’s surface and the radiating height) across the resistor. It is not however equivalent to making the resistance per unit length higher (i.e. increasing the lapse rate) for a certain fixed length of resistor. For Pekka’s example above, it is equivalent to making the insulating layer thicker not changing the material conductivity itself.
Nullius, Thank you very much for your comment. I appreciate its tone and I feel like I learned from it. Your explanation does make a great deal more sense to me than the greenhouse explanations I have heard before. I take it from your later comments that you have been burned at some point regarding these issues and I would like to thank you for going once more into the breech and contributing.
Can I just say what a pleasure it is as a nonscientist to read such a lucid explication? Whether they agree with your science or not, Believers have much to learn from your prosaic style.
The prize for the best comment on the thread goes to Nullius in Verba (3:13pm).
This morning I was going to post more on convection and its apparent neglect but I don’t need to because NV has done it much more clearly and thoroughly than I could.
The bottom line is that you do NOT need absorption of LW radiation by GHGs to explain the surface temperature of the earth.
Everyone should read his comment, then read it again.
Tomorrow I am going to open a new greenhouse thread, pulling what I regard to be the most lucid explanations of the various positions in this.
Paul,
We need to be careful on this point. The greenhouse gases (mainly H2O) are opaque to IR, which is why the IR-visible surface emitting to space is not the solid surface, but higher up. The fact that they are GHGs is important. It’s not purely a pressure effect, either.
A completely transparent atmosphere would give an average surface temperature of -20 C, and convection (which would still occur given uneven illumination) would result in an atmosphere that got even colder than this with altitude.
There are thought experiments that I’ve gone through in previous debates in which it is possible to get a greenhouse effect without greenhouse gases – substituting various sorts of high-level clouds instead. There is also a variant on Willis Eschenbach’s ‘Steel Greenhouse’ in which the planet is surrounded by a totally opaque steel shell with a convective atmosphere underneath it. (Willis usually posits a vacuum beneath it in his version.) But I hadn’t discussed them, and they’re a bit more complicated to analyse.
Please expand on ‘increasing CO2 makes the fuzzy layer thicker’. CO2 is still measured in a few hundred parts per million, and some worry about whether the few is three or four. How does even an increase from 300 ppm to 600ppm provide the heating that is claimed? The increase in CO2 of the order of one ten thousandth only.
Latimer,
Even though CO2 (and water vapor and methane) is present in small amounts, it is an effective absorber of certain wavelengths of long wave radiation, with the amount of absorption related to the concentration. There is a distance near the ground that results in 50% absorption (of those wavelengths) for CO2 that is a few hundred meters. This is an exponential type absorption. Twice the distance and 50% of the remainder is absorbed, and so on. The gases that absorb also emit. If you went 10 path distances, less than 0.1% gets through, so the energy is pretty much absorbed. However, as you go higher in the atmosphere, the lower gas density results in that absorption distance increasing, until at some height, the radiation is not absorbed and goes to space. This is not a thin layer, but spread out. Adding more CO2 shortens the absorption path, and slightly raises the effective height of outgoing radiation. That is what is meant by a fuzzy layer of outgoing radiation.
The fat content of skimmed milk is about 0.3%, or 3,000 ppm, and yet it is effectively opaque to the eye. If you dilute it by a factor of ten, do you believe intuitively that you will be able to see through 10 km thickness of the stuff?
It’s a common question, and quite reasonable, but hopefully the milk example should help the intuition.
Ummm
Fat molecules are much bigger than CO2 molecules…and form large clusters. I think that milk is effectively an emulsion or a suspension, not a solution of fat molecules.
But we are talking about (effectively) a gaseous solution of N2, O2, VH4 H2O etc as well as CO2. I don’t think that your analogy stands.
Sorry CH4. I don’t know of a vanadium tetrahydride. But I had an undergraduate tutor who would have revelled in trying to make it – and probably have blown up his lab in the process.
Fat molecules are bigger, yes, which will increase their area by a factor of ~50 (order of magnitude). Feel free to dilute further to account for that.
It is also true that it forms an emulsion of droplets, but this only means that the gaps between the droplets are even bigger.
It’s only meant to be a simple example to aid intuition.
OK -I think what you are trying to say is that if i looked at the atmosphere at some particular IR wavelengths, then a bit of CO2 would act like a dye, and would make the whole planet look black.
Fair enough…I understand that bit. But what about the water vapour that is present in vastly greater concentration and is also a GHG? Or the methane that is (apparently) a far more potent (even more blackerer) GHG than CO2. Once all teh wavelength at a particular frequency is being absorbed by one of the gases then adding more of another gas doesn’t get to absorb more radiation. there aren’t deeper and deeper shades of black.
I’d add that like others, I very much like your clear style of explanation, but in this case I think a few diagrams would help immeasurably.
The pictures and related explanations of John Nielsen-Gammon might help even more.
This link has been given in this discussion at least twice before, but it is worth it. Unfortunately the third part of the presentation is still missing and a major part of the argument should be there.
Each of the greenhouse gases (or Tyndall gases if J. N-G. gets his wishes fullfilled) is influencial exactly because they are effective at different wavelenghts. Water wapor covers most, but leaves a major gap for the others.
Nullius in Verba:
Why does “Increasing CO2 in the atmosphere make the fuzzy layer thicker, increases the altitude of the emitting layer, and hence its distance from the ground.”
Very nice! This at least gives the flavor of the complexities, and helps explain the confusion that is obvious wherever this topic arises. I am particularly interested in the idea that some calculations “use averages as being representative, and that’s not valid when the physics is non-linear.” The challenge of non-linearity pervade climate science, so it is not surprising to find it here too.
” Our general argument consists of the following elements:
…
2. the analogy to a greenhouse”
Can you quote any scientific source in the last 50 years or so that has based the argument on the analogy with a greenhouse?
Does NASA count as a scientific source?
“Certain gases in the atmosphere behave like the glass on a greenhouse, allowing sunlight to enter, but blocking heat from escaping.”
http://climate.nasa.gov/causes/
less (IMO) on the issue of climate than I would like. lol
Well, it is badly put by whoever wrote it (although it’s true that glass has those properties). But there are any number of patient explanations that greenhouses and the GHE are different. For example, contrary to this post’s claim that
“The IPCC reports never actually explain the physics of the greenhouse gas mechanism.”
the AR4 does have a FAQ 1.3 on that, and they say:
“The glass walls in a greenhouse reduce airflow and increase the temperature of the air inside. Analogously, but through a different physical process, the Earth’s greenhouse effect warms the surface of the planet. “
I was not sure, were you making a joke about the quality of the IPCC report or are you suggesting it is a good explanation?
The quote is not the explanation – it’s an intro remark. The FAQ itself is brief, and not a completely detailed explanation. But it isn’t nothing.
Yes, I agree that “Analogously, but through a different physical process,” is not quite “based on […] the analogy with a greenhouse”. But it’s not an explanation, is it?
It’s also noticeable that the “like a greenhouse” argument doesn’t evoke the same level of vituperation from climate scientists as the typical sceptic argument.
Not when communicating to the public on their public outreach sites, they have made some real boner mistakes in this regard. I have no idea who they have writing this stuff.
True. You and I can look at it and immediately see it as nonsense. It has evidently churned out by some poor PR type who’s been told to “knock up some outreach pages on climate change”. But Joe Public is only going to see the name “NASA” at the top of the page and he’s going to assume his tax dollars have been well spent. I mean, they launch space rockets to Saturn, don’t they?
More, he’s going to assume that the thousands of scientists scouring the web for inaccuracy (it’s amazing how fast they pop up when some new sceptic paper or argument hits the net) would have seen it and let NASA know and insisted that it be corrected. After all, that’s the sort of diligent fact-checking and public peer review by which scientists assure us of the quality of their work.
The poor PR hack didn’t just make it up. These explanations abound for a reason. Some scientist told them that. Many others shrugged and let it pass. Such carelessness and lack of principle is why we are where we are today.
Not peer-reviewed, is it ?
Simple, document properties lists authors.
Randal Jackson, Cecelia Lawshe, Justin Moore, Joshua Rodriguez
google each name with the word nasa, they are web developers
I doubt web developers write the technical content.
Nasa is dumbing down a simplistic analogy to convince the masses.
After reading Vaughan Pratt’s little history, I sort of think we should keep GHE.
I didn’t went through all the comment, but it seems that there are two main points:
1-) Co2 is the main driver of climate.
2-) Water vapor is the main driver .
The biggest problem to solve which one is true, is that there exist no experiment that can be repeated time and time again showing the same or similar result.
The use of computer model thus becomes necessary, but since there is a lot we don’t understand about the atmosphere, they require some assumption about these unknowns.
So everyone agree that Co2 and water vapor are GHGs. But no one agree about these assumptions that cannot be proven wrong or right by anyone.
What doesn’t help to understand the physics is the uncertainty associated with all the data set and mainly the surface temp, sea and land.
The question is, how can we know anything if we can’t be sure of that the data used is good enough. Well other than Co2 and water vapor are Ghgs.
Sylvain,
It is the Sun that is the overall driver of climate. Greenhouse gases cause a slightly higher overall level in ground temperature, and water vapor is the main greenhouse gas. Clouds are also very important factor. Other greenhouse gases like CO2 and methane, and aerosols, also affect the details. The ocean currents (which have long period cycles) and location of land are also major factors (land shifts over long enough times). It gets even more complicated, since many of the processes involved are non linear chaotic process, and result in unknowable long range results. Did you ever hear of the butterfly effect? Computer models are basically a joke for long range forecasts of even trends.
Part of being a scientist is knowing how much weight to place on ideas as they progress from hypothesis, to experimental testing, to provisional theory, and eventually established theory. Though I am skeptical of the IPCC consensus, most of the alternative theories you cite aren’t worth mentioning.
The appropriate path forward for Claes Johnson’s hypothesis is to identify a physical situation where the standard theory of atmospheric radiation makes different predictions than his theory. Then do the experiment (or review the existing evidence). Claes Johnson hasn’t even proposed such an experiment. Until then, his theory isn’t worth mentioning because there is plenty of experimental evidence supporting of the standard theory (particularly observation of downward long wavelength radiation, DLR, expected to be emitted by GHGs).
In their reply to Halpern, G&T agree that DLR from the colder atmosphere to a warmer earth is compatible with the 2nd Law, as long as more radiative energy is flowing in the opposite direction. Therefore, they do not object to the fundamental mechanism behind “greenhouse theory”. (The nature of their remaining objections is not clear to me.)
As for Slaying the Dragon, I got as far as: “Redirecting radiant energy back to the source cannot increase its temperature”. If that energy can be absorbed (as DLR can), this statement is incompatible with the law of conservation of energy! Do the authors confront this dilemma?
Frank
…….”In their reply to Halpern, G&T agree that DLR from the colder atmosphere to a warmer earth is compatible with the 2nd Law, as long as more radiative energy is flowing in the opposite direction. Therefore, they do not object to the fundamental mechanism behind “greenhouse theory”….
This radiative interaction however does not HEAT the colder Earth surface.
The Halpern group rebuttal mistook this for “the photons not arriving at the warmer surface.
Hence their rebuttal completely missed the target and so G&T paper has not had a serious challenge.
This is unfortunate since science only progresses through constructive criticism.
I’m sorry but did you even read our paper? That was never our interpretation.
Yes I read the final draft.
Further months before publication I had a blogging exchange with Joal Shore on WUWT.
I pointed out that the on the existing draft interpretation was comletely unreasonable.
Its a pity that so much effort went into a missed opportunity.
So what is your principle objection to G&T?
Frank, can you please give an example in the real world of when reflecting radiant energy back to the source can increase temperature?
Frank – you say you are “skeptical of the IPCC’s consensus.” If you get a moment, please could you briefly state the nature of that skepticism. Thanks
Frank,
I asked a specific question and am looking for an answer.
Was there a Doctor (of physics) in the House?!?
During the question and discussion portion of the House Science & Tech…Hearing on Climate Change held November 17th, some fleeting comments on atmospheric physics seemed alarming. Lindzen had a different understanding of responses around saturation vapour pressure than Cicerone (55:55-58:30). Lindzen also had an understanding of how molecules reacted to infrared radiation that differed from his colleagues and that left him wondering aloud if the testimony of his panel-mates had much worth (discussion leading up to 1:20:47).
http://www.cspan.org/Watch/Media/2010/11/17/HP/A/40918/House+Science+Technology+Subcommittee+Hearing+on+Climate+Change+Science.aspx
(N.B. The host of this blog was part of a subsequent panel, but I would have liked to have heard her thoughts.)
D Gemmell
Lindzen was correct, but the smear at his colleagues was hardly justified. First of all, bringing up things like “dipole moments” is hardly necessary in a congressional testimony. In fact, it’s only the 3-atom gases that are vitally important as greenhouse gases on Earth, as the 2-atom molecules he mentioned are decidedly higher-order effects. When we think about the terrestrial greenhouse effect, in addition to clouds, nearly 100% of the effect can be approximated by thinking about water vapor, CO2, ozone, methane, and nitrous oxide. Humans have made some CFC contributions as well but it’s pretty small. O2 and N2, which is the bulk of the atmosphere, don’t have the properties to make a dipole moment.
There’s always some caveats to the 1-sentence descriptions of what makes up greenhouse gases, and so forth. For instance, there are opacity features, especially for water vapor, that don’t come from ‘lines’ but from ‘continuum absorption’. There are also situations where the diatomic gases can in fact behave as greenhouse gases. This is particularly the case in very dense atmosphere like Titan, and is important as well on the gaseous planets in the outer solar system. Hydrogen is the predominant greenhouse gas in the context of the solar system. For solar-like stars, the dominant source of continuum opacity in a stellar spectrum (at optical wavelengths) comes from H- (Hydrogen with a second electron in the bound state)
I think if Dr. Lindzen matched smear-for-smear his schedule would be blocked out for the next several years.
If you can give me quotes from their written testimony or oral testimony, I can respond, but not sure what you are referring to?
I could not find a transcript so I only offer, with apologies, this highly edited report:
Inglis inquired about how much warming would result from a doubling of CO2, which in the course of their responses and explanations about CO2 and additional forcings from water you heard this:
Cicerone (56:00-): “…disproportionate amount of evaporation increase as we warm a body of water…A fact of physics…which Dr. Lindzen denies…”
Lindzen(56:41-): “…Clausius–Clapeyron relation…the saturation vapour pressure…for water as a function of temperature…[but] the atmosphere…is almost never saturated…[water bottle and cup prop example]”
Cicerone (57:21-):”…I know the relation he’s speaking of [but] I don’t understand what he’s saying.”
(One would have to watch the video to see Lindzen’s bottle and cup demo to see what confused Cicerone.)
Lindzen stated that because the atmosphere isn’t always saturated the Clausius-Clapeyron relation was not applicable. Cicerone replied that an approximation could be used and despite Lindzen’s protestations one couldn’t hold back the vapour pressure of a liquid despite the saturation of what it is evaporating into. (58:30 the subject is dropped, but not necessarily resolved)
Later:
Baird (1:19-): “How does a relatively small trace element impact…temperature?”
Lindzen: “…there is no simple relation between the amount of a constituent and its ability to absorb radiation…CO2 is a significant absorber, I differ with my colleagues about the reason why, it’s the permanent dipole moment that is important…[other explanations about why CO2 absorbed radiation, involving numbers of atoms, had been offered previously by other panel members] I don’t know, it makes me wonder about their testimony. But still, it is possible for a trace gas to be important…”
“Crimes against humanity”
Lol
Judith, if you’d like to convince this skeptic of the fundamental correctness of AGW, first offer a proof that the adiabatic lapse rate is an equilibrium configuration with zero convective flux so that +/- deviations lead to +/- convective fluxes. My own math indicate that, for an ideal gas in a gravitational field, the configuration of maximum entropy is isothermal and the adiabatic profile requires a significant convective flux for its support.
The assertion of ‘convective equilibrium’ is a convenient AGW ‘trick’ to keep convective flux at the zero level and leave radiative transport dominant. I’ve no quibbles with the basic Schwarzschild flux calculations. Of course, when I calculate the net radiative flux at the surface and the tropopause (MODTRAN), the latter’s twice the former. Radiative surface cooling to be sure, but how do I then restore this steady energy deficit without a steady convective flux and still claim the profile to be adiabatic? And then, if convection can balance a substantial radiative cooling flux, why should it not be able to also influence much smaller GHG increments?
Richard Lindzen has repeatedly stated the essential question of skeptics is climate sensitivity. (I’d add a phrase on the effects of convection on sensitivity.) A clever youngster, once told there’s 250W/m2 coming out of a tropopause 65K cooler than the surface, came up with an Ohm’s Law sensitivity of 3.8W/m2/K and, then given a 5W/m2 forcing for CO2 doubling, deduced a temperature increase of 1.3K. Anyone think they’re smarter than a 5th grader?
Quondam,
I started out thinking the equilibrium configuration with zero convective flux would be adiabatic, but found the approximation I was using was not correct. You are correct it would be isothermal based on maximum entropy.
However, the day/night and latitude variation of solar heating, along with planetary rotation and evaporation and condensation, generate strong mixing. The solar heating is mostly absorbed at the ground (and seas), so heated air at ground level causes buoyancy, which causes large convection currents upward. These currents carry most of the energy upward. The result is that for the Earth, there is no chance for isothermal to dominate. In fact, if you initially had an adiabatic lapse rate and zero radiation and convection occur (and assuming rotation did not matter), it would take MILLIONS of years to convert the adiabatic profile to isothermal due to the very low thermal conductivity of air. It doesn’t take much mixing at all to maintain an adiabatic lapse rate. Your argument does not show anything about AGW.
Leonard,
My own estimate of relaxation by thermal conductivity is about 10^4 years, but that assumes uniform temperature gradient configurations. Thermodynamics indicates nature likes to get things done as quickly as possible (max. entropy, etc.) and if that entails inhomogeneous configurations with regions of higher than average lapse rates, sobeit. Suppose we have an pure N2 atmosphere. Surface heating of the atmosphere will heat it and turbulence spreads it around, but once in the air, that energy has no where to go – no IR absorption, no IR emission – and the entire atmosphere warms to the surface temperature ca. 255K. Roy Spencer blogged on this point a year or so ago. The questions I ask: If we step the surface temperature, how long does it take for the change to reach the 10Km altitude? Is there a difference between plus and minus steps?
Quondam, there would be a huge difference. With a plus step, warm rising thermals would take the change up into the atmosphere very quickly, but with a minus step there would be no convection so it would take ages.
Quondam,
Excuse my comment on millions.That was for Venus. Earth is more than an order of magnitude less. Also the exact level of residual gradient enters the calculation.
“My own math indicate that, for an ideal gas in a gravitational field, the configuration of maximum entropy is isothermal and the adiabatic profile requires a significant convective flux for its support.”
I had a little trouble with this concept a while back also. How I resolved it was to think about what constituted a significant convective flux. I imagined smaller and smaller altitude differences until reaching molecular thermal motion range. Convective flux, though small, is still in effect at that level. Adiabatic temperature profile is self maintaining at the atmospheric molecular level. It is not necessary to have big updrafts and downdrafts.
Anyway, that is how I have it worked out.
If an atmosphere was transmitting to sunlight but a near perfect optical absorber for Earth’s thermal radiation, but still had the same location of outgoing radiation to space as the Earth, the average ground temperature would be the same as present. The radiation up would exactly balance the back radiation at the surface and near surface, and all of the energy from solar heating would be transported up to radiate to space by convection only. This is the case of what it would be like with much more CO2 and other greenhouse gases, but note the critical assumption of where the radiation to space occurs.
Note that back radiation and even amount of greenhouse gases did not matter. Only the LOCATION of outgoing radiation and the fact of the adiabatic lapse rate. THE BACK RADIATION DOES NO HEATING ON THE AVERAGE. It is a result of, not cause of the atmospheric greenhouse effect.
The only important effect of adding some CO2 to the present Earth’s atmosphere is to raise the location of outgoing radiation a small amount.
There may be feedback effects, but even they only change the effective outgoing height a small amount more or less.
So, the CO2 and water vapor feedback will warm. The more CO2, the more warming, the more feedback, until a new equilibrium is reached. But then, the oceans cool, which in turn cools the atmosphere, and also absorbs extra CO2. This reduces the CO2-related warming. The oceans have to be the proximate driver of air temperature because air has such a minuscule heat capacity compared to the ocean. So then the question becomes what determines the temperature of the various parts of the oceans. That probably would be the large ocean currents and solar SW radiation. So the currents cause delayed effects from changes in insolation. Then the question becomes what controls the incoming SW? GCRs? Clouds? Something else?
Your chain of logic broke apart after sentence 2. Why do the oceans have to cool?
Nothing ‘controls’ the incoming SW except for the sun and the distance to the sun. The degree of planetary reflectivity (albedo) modulates the fraction of that incoming energy that is absorbed, but there’s no reason the albedo is going to act to stabilize the climate.
I was thinking about Joe Bastardi’s prediction that we would undergo an era of cooling due to negative AMO and PDO. If there are volumes of ocean water surfacing that are less warm than we have experienced lately, then we could cool due to the ocean cooling the air. (I really don’t see how the air could cool the oceans except over a very long span of time, do you?). Galactic cosmic rays could modulate cloud cover, which would the modulate the heat absorbed by the oceans. More or less heat absorbed would determine the water temperature in various ocean currents, which could submerge and re-emerge to heat or cool again.
Chris,
Your comment that “there’s no reason the albedo is going to act to stabilize the climate” is interesting. You are positive cloud formation due to some warming is not going to act as a negative feedback by changing albedo? What do you base this certainty on? Roy Spencer and Lindzen seem to think otherwise.
I’m glad your entire position is based on what two scientists think in the face of the whole community, but there’s just no evidence for it (and generally they think on the OLR side of the equation anyway, not the albedo). The papers they have certainly have not convinced anyone, and for good reason. There’s also some papers showing low clouds thinning in a warmer climate. Another example is the Clement paper, but mostly the observational and paleo record just doesn’t work with your implied sensitivity. It’s not a settled topic but the magic stabilizing ideas are just wishful thinking
Chris,
Take a look at this. His statement of CO2 rise is off (15% not 20%), but this is not important for the remainder:
http://www.palisad.com/co2/eb/eb.html
He also has a slide show at:
http://www.palisad.com/co2/slides/siframes.html
Judith – I have questions on this but they would be off topic. Could we have a thread on what we know/agree/disagree about clouds please?
This is coming eventually. Will have a series on climate sensitivity, then will dig into water vapor/lapse rate and cloud feedback processes. There will be a long series on clouds and interactions with aerosols. In the new year.
If we get an increase in cloud cover equivalent to permanently whitening the area of the US, we would get a one degree C cooling out of it (1% albedo increase). I think we would notice if this was happening, but I won’t say it is impossible, because increased haze did this to cause the, maybe, 0.4 C cooling up to the 70’s, and new areas are industrializing now. This effect could offset the 3-4 degree CO2 effect by maybe another half degree, in my view.
The problem you are having communicating the back radiation component comes from your using the idea that less cooling = warming,
and less warming=cooling…
With the addition of more CO2, the back radiation slows the exit of surface heat 24/7 like insulation in a house wall, during the night the minimum temp drops slower so is higher at sunrise, since the dew point is the factor to consider for the specific heat content, the less the near surface air cools over night the higher is the resultant dew point the next day (that can result on average) as more moisture is left in the air, (was not precipitated out as fog, dew, mist or rain, snow).
The increase in latent heat does not show up on a thermometer, as the sun increases the temperature (thermal input) the next day the higher specific heat from what ever increase in dew point is left over (above the initial lower CO2 sample) allows the air to absorb more Jules for the same increase in temperature you had the day before (results in greater latent heat, and higher dew point), which allows more convection to form as the increased moisture content is + feedback for convective forcings.
The slight increase in convection leads to a greater probability for more overall cloud cover than the initial conditions, which is an immediate (next day) feedback that increases the albedo, slowing the heating from less SW absorbed, just enough to keep the dew point and resultant specific heat content of the air mass regulated.
If the night dew point increase causes less night time low level clouds and fogs, it allows more time for radiant heat to be lost before the sun rises, then increasing the SST in the day before clouds return in the afternoon.
Colder ocean surface temperatures from up welling, do not cool the air above it, it only warms up more slowly, so the air ends up cooler from less heating, and slightly less outgoing radiation. IF the dew point is higher than the upwelling SST then condensation from the air mass will form on the surface, leaving the heat of condensation in the skin of slightly less saline concentration.
The only way volumes of sea water down wells, is from the formation of sea ice, forcing out the extra salt that increases the density of the 2 to 4C degree (more saline) denser down flows that drive the polar cold ends of the global sea currents, Convection stops the less dense/saline skin of warmer (due to heat of condensation of water vapor out of the air) sea water from down welling.
It is when the ocean surface temperature starts to climb above the dew point, that the vapor pressure drives moisture into the atmosphere carrying the increase in latent heat and some temperature increase.
In the models there is no compensation for the ion content of the near surface air containing the sea spray moisture droplets, and aerosols from plant respiration, which can shift the balance in the distribution of particle size of droplets in the fogs, and clouds that form, the greater the mutual static repulsion between drops as the overall static/ion charge builds the smaller the droplet size, the more transparent the fog or cloud is to solar SW passage.
When the solar wind density increases, the increased magnetic flux increases the homopolar generator fields in the geomagnetic fields, which ends up increasing the positive ion content along the equator. Increasing the resultant pole – to Equator + standing charge gradient on the Earth which reduces the cloud density in the mid latitudes, allowing more solar SW to reach the surface.
By this mechanism the increased solar wind activity (with no or little change in TSI) can cause resultant warmer SST’s, driving short term increases in severe weather tornadoes and hurricanes. The North / South declinational tides of the moon shift the global atmospheric meridional flows in phase with the magnetic pole rotation of the sun and hence the polarity of the solar wind shifts in phase with the declination peaking around culmination, which can be shown to account for the increased production of tornadoes at 3 days either side of culmination.
Ion production and discharge globally by homopolar generator processes give an ion assist additional to the thermal gradient across frontal boundaries that form in the mixed air masses that combine to form the tidal bulges, to drive the local precipitation rates above usual, generating narrow frontal boundaries with tornadoes, drechieos, flash floods, and other severe weather types.
Very interesting analysis Richard, and given support by Dst measurements of the horizontal magnetic field. The positive component correlates with solar wind speed, and the negative component correlates with solar activity.
http://tallbloke.wordpress.com/2010/11/24/earths-magnetic-field-mimics-solar-activity/
I’m just a layman lurker, but I get tired of the entire “CO2 absorbs infrared” bit. Of course that’s true. What’s important is the net effect, and that’s far more complex.
For example, increased CO2 increases plant growth. Does it increase it enough to offset the slight warming effect of the CO2 as plants absorb more solar energy in the production of biomass? Does anybody care? As an erstwhile motorcyclist, I know the temperature difference between green fields and bare dirt can be pretty dramatic.
You get tired? Imagine how tired scientists get every time someone thinks they’re the first one these things have occurred to. No, Pops, nobody’s considered the net effect, except maybe (Solomon 2009), (Peng 2004, (Tao 2008), (Morgan 2007), (McCabe 2007), (Cai 2008)…
Solomon 2009: asserts irreversible changes due to increases in atmospheric CO2.
Peng 2004: simulation models show decrease in rice yields due to increased night-time lows.
Tao 2008: incorrect URL provided.
Morgan 2007: changes in plant varieties due to warming.
McCabe 2007: warming may create water supply shortages.
Cai 2008: impact of rising temperatures on inflows in Darling-Murray Basin.
At this point I begin to wonder what question you thought you were addressing with these references. So I’ll repeat: what is the net effect on global climate of increasing atmospheric CO2? Does it get hotter or cooler, or no change?
I also get tired of chasing irrelevant references.
warming.
On what basis?
It looks like I’m not the only one who wondered about this – check out this paper from NASA…
NASA quantifies Negative biomass feedback
See also:
Bounoua, L., G. J. Collatz, S. O. Los, P. J. Sellers, D. A. Dazlich, C. J. Tucker, D. A. Randall, 2000: Sensitivity of Climate to Changes in NDVI. J. Climate, 13, 2277–2292. doi: 10.1175/1520-0442(2000)0132.0.CO;2
Please pardon my ignorance.
My laymans understanding so far, (having read numerous articles and literally thousands of comments on both sides of the debate) is as follows..
There are only 2 ways a greenhouse warms earth (earth includes it’s atmosphere, which is part of the system, only less dense than the surface).
1-) Reduction of the atmospheric window, where radiation escapes directly from the surface to space.
2-) GHGs delaying the escape of radiation to space due to the so called trapping or back radiation.
So some questions.
Has there been any observations that demonstrate the atmospheric window has reduced during this latest warming period?
If so, by how much has it reduced and how does this reconcile with the measured rise in global Ts and the Keel Trenberth energy budget?
Considering radiation travels at or about the speed of light, how long is the above mentioned delay due to back radiation in an atmosphere of a few kilometres. Seconds? minutes? weeks or years?
If the answer to the above is any longer than hours, why do Ts plunge so dramatically during clear sky nights, and why is the ground always warmer than the atmosphere?
As an addendum, do the radiative properties fo GHGs behave differently during daytime to nightime? If not, why would an EGHE manifest itself mainly in the rise of minimum Ts i.e. mainly at night? Why wouldn’t they “do their work” at all hours of the day?
thankyou in advance
Changes in the Earth’s radiative fluxes are hard to measure but there’s been some work done on this, e.g., Harries et al., 2001 and some of the follow up papers he has done, e.g., Chen et al 2007
Thankyou. I hope they’re not behind a paywall
I would ask the skeptics whether they agree with the following statement: A rotating sphere at the earth’s distance from the sun with an albedo of 0.3 will have a radiative equivalent temperature of 255 K. Yes or no?
Hopefully, if they know basic physics they will say yes.
OK, so why doesn’t the earth’s surface temperature average -18 C, but nearer +15 C?
Explain this your own way.
Now in reality, the radiative temperature of the earth is 255 K, but it comes from the atmosphere. Note that radiation can only come from an atmosphere with IR-active gases, such as H2O and CO2, not from pure N2 or O2 which are transparent to IR. On their own O2 and N2 would leave the surface to radiate at 255 K.
The rest of the explanation is that since the earth has to radiate at 255 K, and there is an atmosphere helping to do that, and we know the atmosphere gets warmer as you go deeper (actually because of convection and compression), the surface will be warmer with this type of atmosphere than without.
Jim D,
You seem to have not been reading the comments. Several skeptics have discussed the atmospheric greenhouse effect, which is real, but the actual issue is the nature of the feedback, not if is there a CO2 effect. There are some skeptics that think there is not a greenhouse gas effect, but most who are scientists agree there is one. Locking in on outliers of either side of the issue is chasing straw men.
Unfortunately I read most of the 200 comments, but the item at the top and most of the links listed there were related to complete denial. I expect JC was going to have a separate thread on feedbacks once we get this and maybe other basic building blocks established first, and I will contribute on it when that time comes.
Jim D, OK, it can be hard to find the quality comments among the dross, but please read the comments by Leonard Weinstein and by Nullius in Verba. You do NOT need IR-absorbing gases. You just need an atmosphere. NV’s argument is in terms of convective lapse rates. If you prefer a radiative argument, think of the atmosphere ‘back-radiating’ to the earth (warm N2 radiates as much heat as warm CO2!), and the heat getting back into the atmosphere from the earth by thermal convection. In other words, think of the standard GHG argument but with the earth -> atmosphere heat transfer by convection instead of IR absorption.
See comment above.
http://judithcurry.com/2010/11/30/physics-of-the-atmospheric-greenhouse-effect/#comment-17275
So you look at radiation codes like MODTRAN (find the U Chicago site where you can play with it), and you think they are part of the big plot, despite these theories being developed decades ago? These adequately quantify the greenhouse effect. It is well understood at the molecular level. Why look for something else? First you have to show that MODTRAN is wrong despite matching spectroscopic measurements. Then you can come up with an alternative theory.
N2 doesn’t radiate anything. Where do you get that from?
At the expense of embarassing myself I’ll give it a shot.
yes or no?….Yes
Why 15C and not -18C?….Conduction???
That was a very interesting question.
I have one that is also (to me at least) just as interesting.
A rotating sphere etc etc but with a non-GHG gaseous atmosphere. (Say N2 and O2 only) Given enough time, what will the temperature be?
ooops, just to clarify that question, “what will the Temperature of the atmosphere be?”
The temperature will be ideal. No humans. No CO2. Paradise as envisioned by Hansen et al.
Apart from the plants – notable by their absence. Or most any other form of life.
Haha ha Latimer, I like the humour.
Still, it’d be nice if someone could help me with the answer. I assumed (yes assuming is dangerous and I barely have high school education) the physics involved would be much simpler than when GHGs are involved.
Anyone willing to help with an answer would be much appreciated.
The global temperature will be constrained to be no greater than 255 K (with modern albedo). There’s been modeling experiments done that remove most of the greenhouse effect (like the Lacis et al. results) and the temperature drops even further than that.
Thnx CC. Your answer surprises me, -18C.
How does the atmosphere lose it’s heat if it can’t radiate to space, at least nowhere near as efficiently as if it contained GHGs?
(I probably shouldn’t be taking up time and space on a technical thread).
I would have assumed that the GHGless atmosphere would accumulate heat until it reached the same T as the surface.
I’ll see if I can access Lacis et al
Baa,
To explore this further,
You can see all of this by starting with the most basic energy balance equation:
S*0.25*(1-a)=σT^4
where S is the solar constant (roughly 1370 W/m2), a is the albedo (~0.3), 0.25 is the cross-section to surface area geometric ratio that must be accounted for (this will always be this value unless the object of interest is not spherical), σ is a constant, and T is the emission temperature. The left hand side is the incoming absorbed sunlight, and the right hand side of the equation is the outward power output (energy per unit time) per unit area. Solving for T yields ~255 K. Note that since we are dealing with no opacity, the emission temperature is the surface temperature.
I’ll note that both the atmosphere and the surface become very cold in the limit of no infrared opacity. If the atmospheric opacity is very small, the ratio of the temperature at the top of the atmosphere (TOA) to the temperature at the bottom of the atmosphere (BOA) will be about one. As the atmospheric opacity increases, the atmospheric temperature gradient will increase, and TOA:BOA temperature ratio will decreases, going to zero in the limit as the opacity approaches infinity.
As opacity increases, the emission temperature will stay the same (~255 K) except that it is no longer the surface temperature, but rather some temperature encountered high in the atmosphere. In the real world where we have to deal with varying degrees of opacity depending on the wavelength of interest, the primary source for low opacity (highly transparent) wavelengths (the so-called atmospheric window) is near the surface. The primary source of flux for high opacity (low transparency) wavelengths is in the high atmosphere, ranging from perhaps the middle troposphere near the wings of the spectral lines to the stratosphere at the center (at least for CO2, ozone works a bit different). In a simplified “grey” atmosphere where we sort of average over the the spectrum, this average emission height is about 5 km (call this height H) in the modern atmosphere. You can thus extrapolate down the adiabatic lapse rate (L) to achieve the surface temperature.
T_s = T_e + (L*H)
and so T_s > T_e in the presence of an IR absorbing atmosphere. Physically, the decreased flux from the opacity is causing a total decrease in the outward energy term of the planet. If there’s no greenhouse effect, this doesn’t happen and the surface must equilibriate with the only incoming energy term, the absorbed shortwave radiation.
Thankyou for so much detail, and I apologise for the late reply.
ok, so my planet with a GHGless atmosphere would have a uniform T from ground to TOA of 255K?
{You said above “If the atmospheric opacity is very small, the ratio of the temperature at the top of the atmosphere (TOA) to the temperature at the bottom of the atmosphere (BOA) will be about one.”}
Whilst researching the constant (SB Constant) I came across this in Wiki…
“With the average emissivity set to unity, the effective temperature of the Earth is:
TE = 254.356 K or -18.8 °C.
This is the temperature of the Earth if it radiated as a perfect black body in the infrared, ignoring greenhouse effects.”
Which agrees with you. But then this, from the same paragraph…
“If we wish to estimate what the temperature of the Earth would be if it had no atmosphere, then we could take the albedo and emissivity of the moon as a good estimate. The albedo and emissivity of the moon are about 0.1054 and 0.95 respectively, yielding an estimated temperature of about 1.36 °C.”
Do I have this right Chris, a virtual earth with an atmosphere of N2 and O2 only yields T=255K, but one with no atmosphere at all yields T=274.36K? meaning an atmosphere of N2 and O2 is cooler?
How can this be? Surely the N2 and O2 molecules receive some energy via conduction, with no way to emit that energy (non-GHG) therefore accumulating from the ground up until it’s T is uniform from BOA to TOA, and also receive some energy via direct sunlight (diurnal bulge?)
Chris all this may be quite tedious for you, if so, I fully understand.
Ooops looks like I overdid the bolding (he says sheepishly) sorry JC
“but one with no atmosphere at all yields T=274.36K?”
The second calc used a different albedo – the moon’s – which is lower. Also emissivity=0.95. Both changes make it warmer.
Baa Humbug,
Not tedious at all. I like that you are phrasing your queries as questions, rather than bold assertions about the status of climatology and the morality of the scientists who study it.
The albedo is an intrinsic property of the planet/moon (depending on cloud cover, land surface characteristics, and particles/molecules in the atmosphere itself)– it has nothing to do with the distance to the sun, so I’m not sure why we would assume the moon is a good analog to Earth’s no-GHE albedo parameters. It could be, but that would just be by coincidence. Albedo is also a function of the climate itself. Snow, ice, and clouds have humidity and temperature thresholds at which they form and dissipate, making them potential feedbacks to climate change, effects which are largely not operable on the moon.
The atmosphere affects the planetary albedo in a variety of ways. First, you get direct reflection from aerosol and clouds. The albedo on Earth is dominated by cloud cover (as you’d see just by looking at a visible satellite image from space. The clouds are very reflective). Some ~5% of the planetary albedo is also due to Rayleigh scattering of air molecules. Then, there are also the affects that atmospheric opacity to downwelling shortwave radiation limits the amount of downwelling shortwave radiation reaching the surface and, finally, atmospheric opacity to shortwave radiation upwelling from the surface that limits the amount of shortwave radiation reflected by the surface that escapes to space (the globally averaged shortwave absorption in the atmosphere is about 20% of the incoming stellar flux).
The land surface (especially snow and ice) are also very reflective, but the land surface contributes only a small fraction of the total planetary albedo. In fact, even in these ice-covered regions, the local albedo is generally dominated by clouds.
In simulations of a greenhouse free atmosphere by Lacis (as well as other papers), the albedo of the planet actually increases substantially. This is, in part, due to the prospect of a runaway icehouse planet, with most or all of the oceans freezing over. This increases the total planetary albedo to over 30%, resulting in temperature even colder than the 255 K value above.
I’m sorry, it looks like I didn’t explain my thought process too clearly. p.s. I wear white T-Shirts in summer.
My virtual planet with an amosphere of non-GHGs would necessarily be one without ice, vegetation etc A similar surface of rock and dust as per the Moon, hence I can see why Wiki uses the Moon as an example of albedo and emissivity properties.
If Wiki is correct (with the moon essentially being the same distance from the sun as is Earth) then a T profile of 1.6DegC would be close to the mark, but probably a little high due to Rayleigh scattering you mentioned.
So, being God, I’ve created a new Earth consisting of rock and dust, an atmosphere of N2 O2 (we’ll disregard Argon etc for this purpose).
My Earth has a T of about…say 0DegC? uniform throughout the atmosphere and surface, meaning no wind, no weather.
I’m now ready to add some GHGs to the atmosphere, but before I do, have I gone wrong somewhere along the way so far?
Baa: I don’t seem to be able to directly reply to your last comment, so hopefully you spot this.
Your underlying premises are not correct. Certainly if the Earth were a bare rock, the albedo would probably be similar to the moon or Mercury in this regard, in terms of albedo. But the land surface can still be different. The albedo on Mars for example is more than double that of the moon, even with a thin atmosphere. Dustiness helps. The albedo of tundra, granite, limesone, desert sand surfaces, etc are all generally higher than ~0.1.
But why does a greenhouse gas-less atmosphere imply no ice? The Earth is some 2/3 ocean, which have plenty of room to freeze over. The moon isn’t. So there’s no reason to take your GHE-free virtual Earth to be similar to that of the moon offhand, and as I stated before, the albedo doesn’t really care that there’s a similar distance to the sun between the two objects. What’s more, if we want to remain in the realm of some degree of realism instead of a complete virtual world, there will also be some hydrologic cycle at work if you took away the non-condensable GHG’s (CO2, CH4, etc) and clouds. You can’t tell the water vapor and clouds to go away in real life, even if you can shut them off in a model. In a wide variety of papers (Pierrehumbert, the Lacis paper, Voigt and Marotzke) all get a snowball in a CO2-less atmosphere, for example, and the albedo increases.
There’s another point to be made too. For airless bodies like Mercury or the moon, the radiative balance equation S*(1-a)/4=σ*T^4, doesn’t hold a lot of meaning. This is just because the right hand side is non-linear and there’s very large diurnal temperature gradient (of several hundred K). In this case, talking about an ‘effective temperature’ doesn’t really give as much insight, as compared to a hemispheric temperature, or even the temperature at a specific point, depending on the problem at hand.
Thankyou Chris, I very much appreciate the time and effort you’ve put in to help me.
I’ve learned a little more.
Try this one
except for the annoying style, its a good start.
Eli,
I read your writeup, and want you to consider the following. If the altitude of outgoing radiation is higher, the temperature of the gas at that higher altitude (and it is actually spread out, but we are both using an average) has to be the same as it was at lower altitude or the amount of outgoing radiation would be lower than absorbed solar radiation! The adiabatic lapse rate is a GRADIENT, not a level of temperature, and fixing the temperature at one location sets the levels. The balance of incoming and out going solar caused heating sets the temperature at the effective outgoing level (255 K). However, we are only talking about 150m or so increase in altitude for outgoing radiation. The same temperature at the higher altitude plus the lapse rate times the higher altitude is the cause of the higher ground temperature. An example of why this is so can be seen in an ideal model:
If an atmosphere was transmitting the same amount of sunlight through an ideal atmosphere to the surface, but the atmosphere was a perfect optical absorber for Earth’s thermal outgoing radiation, but still had the same location of outgoing radiation to space as the present average location on Earth, the average ground temperature would be the same as present! The radiation up would exactly balance the back radiation at the surface and near surface, and all of the energy from solar heating would be transported up to the altitude, to radiate to space, by convection only. This is the case of what it would be like with much more CO2 and other greenhouse gases to completely fill the absorption window, and cut the absorption path to essentially zero. However, note the critical assumption of where the radiation to space occurs. I know this is an unreal idealized model, but correct with the assumptions, and shows the point I was making.
Note that back radiation and even amount of greenhouse gases did not matter. Only the LOCATION of outgoing radiation and the fact of the adiabatic lapse rate (I did have to assume the same lapse rate, which is radiation independent. It is -g/Cp but modified by water vapor condensation). THE BACK RADIATION DOES NO HEATING ITSELF ON THE AVERAGE. It is a result of, not cause of the atmospheric greenhouse effect. You can look at the back radiation as a cause of heating, but that is confusing cause and effect.
We are considering interlinked phenomena. In many cases it is just semantics to argue on what is cause and what effect.
For a surface the backradiation is one of the causes for its temperature. In that sense it is a cause.
The change in the altitude of tropopause may be considered as a cause or explanation for the warming, but it is not the basic cause, but must be explained by something else. For the warming from an increase of CO2 the change in radiative energy transfer is a much more basic cause.
My hope is that a proper way of handling the radiative transfer explaines the change of the altitude of tropopause (and also a simultaneous small change in the temperature at tropopause) so that one can finally come back to offering the radiative processes as the correct approximate explanation of the whole effect (excluding feedbacks) without the need of discussing the temperature profile of the atmosphere.
Pekka,
Back radiation does no heating (on the average). The outgoing radiation is always equal or larger (on the average) than back radiation. Back radiation is an energy transfer, but it is the NET radiation transfer that heats, and the net radiation is always out (on the average). Convection plus the net radiation together transfer the absorbed solar energy to the TOA to radiate to space. That is the mechanism, and claiming the back radiation HEATS the ground is simply wrong.
Leonard,
I made the statement for a surface, not an more extended layer (but similar issues apply to more extended layers as well).
The energy balance determines the temperature of the surface. The back radiation is part of the incoming radiative energy coming to the surface and thus contributes to its temperature. The other components of the balance include emission of radiation by the surfaceas as well as conductive and convective transfer of heat.
The incoming radiation including back radiation are components not affected directly by the temperarture of the surface, all other components are affected byt its temperature. Back radiation is affected by the temperature of the gas.
“the temperature of the gas at that higher altitude (and it is actually spread out, but we are both using an average) has to be the same as it was at lower altitude or the amount of outgoing radiation would be lower than absorbed solar radiation!”
No, it doesn’t have to be the same. There is the atmospheric window. As the emission altitude rises, the whole atmosphere and surface gets somewhat warmer. More energy escapes via the AW. Somewhat less escapes via GHG emission. So the temperature at the new emission point (after GHG increase) is higher at that altitude but lower than it was at the previous emission level.
The surface warming that increases outward IR via the AW comes from down IR. This has increased because the emission level for down IR has been lowered.
Nick,
As greenhouse gas concentration increases, the atmospheric window DECREASES slightly (band broadening). Also the EFFECTIVE height of outgoing radiation is not based on a single height, but an average, consisting of broad areas of different height for each gas, and the atmospheric window. Obviously this is a gross simplification to call it a single height, but since both the reduced window and increased CO2 effective height would increase, my statement (as limited by the crude averaging) is essentially correct. Including all the complex details might cause some temperature change, but not much.
Based on an earlier post by Nullius in Verba (Nov 30, 3:13 pm) and the following posts by him and myself, I try to formulate better how this non-atmospheric physicist understands the situation. I hope this helps in finding more widely understandable explanations.
There are several related issues:
1) Ultimately we need to know the relationship between the surface temperature and outgoing radiation to the space.
2) The bulk of the radiation comes finally from the upper parts of the atmosphere as the troposphere is opaque to most infrared wavelengths.
3) This is the basis for Nullius in Verbas statement that the radiating surface is high in the atmosphere.
4) Some wavelengths penetrate better through troposphere. Therefore there is also direct radiation to the space from the surface of the earth and lower troposphere.
5) The stratosphere is not convectively mixed. Thus the radiative energy transfer dominates in the stratosphere.
6) The effective radiative temperature of the earth as seen from space is about -20 C. The earth is radiating less than it would at -20 C at wavelengths dominated by the highest troposphere and more at wavelengths penetrating well through the troposphere.
7) The temperature of the tropopause is determined by the energy balance of the earth.
8) The altitude of the tropopause and the temperature difference between the surface of the earth and the tropopause are interlinked through the lapse rate, which in turn is determined by the stability condition of the atmosphere and the physical properties of atmospheric gases.
9) Additional CO2 influences the transfer of radiation at those wavelengts where CO2 has absorption, but the absorption is not fully saturated at all relevant distances. Thus it influences the direct radiation from the surface of the earth and the lower troposphere reducing its share in the total outgoing radiation. Stratospheric CO2 influences also the radiation from the top of troposphere and this is effective at wavelenghts where the absorption of CO2 is too strong for the radiation to penetrate far in the troposphere.
10) Any explanation of global warming must specify through which mechanisms the changes in the absorption of infrared radiation influence the parameters of that basic explanation. If the altitude of the tropopause is an essential parameter, it must be linked to the changes in the radiative transfer, and furthermore, possible changes in the temperature of the tropopause and the lapse rate must be analysed.
Explaining global warming may require going through the whole “basic greenhouse effect” with many complications, but it may also be possible to explain the warming as a change in the energy balance without a full description of the atmospheric temperature profile. I hope this more straightforward approach can be formulated in a way that may also be considered correct, while not comprehensive.
The sunny face at point 8 is not intentional, but created automatically by the web software from 8 and ).
I sometimes think it’s an indication that 7 points is as far as you will get anyne else to read. ;)
Sun only provides the energy for heating the Earth. Energy is stored in the oceans and taken back and forth by ocean currents, and this process takes decades and even centauries. Ocean currents are not constant, and are affected by number of factors too. There also volcanoes, geo-tectonics and astronomy (Milankovic).
Some of these come together in the North Atlantic as:
http://www.vukcevic.talktalk.net/CET-NAP.gif
and central Pacific as:
http://www.vukcevic.talktalk.net/PDOc.htm
Do not be mislead: part of the heat affecting today’s temperatures have arrived here from the sun, long before any of us were born.
In long term (within Milankovic formula) the energy from the sun is probably nearly constant , it is just its distribution in time and space that varies, it is all down to the ‘mother Earth’ what she does with it.
Humans and CO2 are nothing but a flee in the elephants tail.
The long term storage of solar energy in the ocean is exactly the reason why equilibrium based calculations won’t give us accurate sensitivity deductions from observation.
Would it be impolite to observe that after 24 hours and 250+ comments from some of the finest brains on the planet – and with the greatest knowledge of this subject available – that we are no nearer coming up with an explanation at any of the levels that Judith asked for:
‘… At an audience that has taken 1 year each of undergraduate physics and chemistry, plus calculus. Once we have something that is convincing at this level, we can work on how to communicate this to the interested public (i.e. those that hang out in the climate blogosphere). Willis Eschenbach’s help is needed in translating this for the WUWT crowd.’
I started out on this one thinking ‘yeah OK – basic greenhouse effect – no probs with that – well understood stuff’. But now I’m less, not more, convinced.
Surely it can’t be that difficult? To explain the absolute basic 100% foundation of everything about global warming because of CO2. The sine qua non. (And don’t call me Shirley :-) )
Nullias in Verba has the best so far IMO.
But Nullias in Verba is not explaining at all the basic first step: How does the CO2 cause the effect. Stating that it makes the fuzzy layer thicker is not a correct explanation. The correct explantion must involve the energy balance.
The thicker fuzzy layer is not the cause, it is an effect of the change in the radiative energy balance from reduced direct radiation from the surface and the lower atmosphere.
I’m predicting that it will take another thread to get this focused. It has been illuminating to hear the skeptical arguments laid out and debated. It will take a little more cogitating to get where we want to be :)
judith given the way skeptic “arguments” spin in a thousand different directions, it might make sense to do a single thread at a time.
Like putting G&T to rest. and moving on to the others. It quite a struggle to
get people to focus and follow an argument through. Perhaps a guest post from Lindzen, spencer etc on RTE.. or working engineers explaining how they use that physics.
tomorrow i am collecting some of the main arguments into a new thread, to try to get some focus. creating the new skeptics discussion thread at least sent the noise to a different location.
It would be good have a thread on each of the major “topics” that either completely disbelieve that GHG’s have a “warming effect” (vs greenhouse) as well as separate threads on those that show the degree of impact that GHG’s have vs other potential causes. It might then be really interesting to seeing “polling” , both of readers and your associates as to their acceptance of various positions. Just a thought
Steven
Refocus please.
The problem here is not that there are a zillion different sceptical arguments. It is that there seem to be a zillion different basic POVs about how the ‘greenhouse’ effect works.
In other words, nobody seems to have a really convincing and defendable position of the basic physics. Some look at complex radiative transfer models, others at the ideal gas law, energy balances etc etc.
But none of them have yet been able to come up with a reasonably simple explanation that we can all agree on about how and why it works.
I don’t doubt that such an effect exists in some shape or form, but it is very disturbing that something so absolutely basic to the whole global warming argument is so poorly understood in detail.
It is not really a tenable scientific position to say ‘we have studied all other factors in detail and can reject them all as being important factors in the climate change we believe we have data to confirm. So (by lack of anything else) it must all come down to this thing we call ‘The Greenhouse Effect’. But when we come to look in detail at the Greenhouse Effect, we find we don’t actually understand it at all. But we did understand all the other factors in absolutely enough detail to reject them as causes. Honest!’
It is just not very convincing.
Don’t blame sceptics for the very poor quality of the basic scientific understanding. The alarmists job is to prove their case. Our job is to point out flaws in the alarmist argument. And this is a big one.
Agreed.
It just goes to show the intransigence with which some hold their preferred beliefs and the futility of trying to fashion a broadly understandable explanation when the responses go back and forth between a rejection on the basis of over-simplifying and rejection on the basis of being too complex to understand without doing an UG course in physics.
As someone noted earlier – when do we hold individuals responsible for their own errorneous beliefs?
It just goes to show the intransigence with which some hold their preferred beliefs and the futility of trying to fashion a broadly understandable explanation when the responses go back and forth between a rejection on the basis of over-simplifying and rejection on the basis of being too complex to understand without doing an UG course in physics.
There is never going to be one “correct” explanation which is at the right level for the public – some people are capable of grasping a more complicated explanation than others, some people are simply more inclined to take the time to try to understand the subject in greater detail. The most valuable thing for a layman such as myself is to have explanations at various levels available so I can educate myself to a level I feel comfortable with – but that’s because I find it interesting, not because I think I neccessarily need to have a more detailed explanation in order to understand the essential principles of the GH effect and how they relate to the case for AGW in general.
As someone noted earlier – when do we hold individuals responsible for their own errorneous beliefs?
Exactly – Judith’s statement
“The fact that such papers are being written by scientists who take themselves seriously and are being published implies to me that scientists have done a poor job of explaining and making the case for warming of the planet by gases such as CO2. ”
seems to me to be not just unduly harsh on herself and other scientists who accept that the GH effect is real, but also incredibly naive.
Tosh.
The problem here is not that of ‘trying to fashion a broadly understandable explanation’. It is that nobody seems to have a defendable explanation at all.
Do not blame sceptics for pointing out that just about everything we’ve heard on this thread so far has big holes in it. If the explanation of any theory doesn’t hold water and can’t be defended against simple criticism by non-experts, then the problem lies with the explanation, not with the nature of the critic!
Focus your attention on the science, not on the sceptics. If you guys really can’t come up with a proper explanation of the greenhouse effect your case will take yet another damaging blow.
Latimer,
The fact that no one on this thread has presented an explanation that is to your liking does not mean that no explanations available. Go and read one of the standard text books on the subject if you are really interested. Also read Science of Doom’s comment below (or visit his website – I’m sure there is something on there about it).
It seems to me the experts here are doing just fine at defending the criticisms by non-experts. The problem is they can do so until they are blue in the face and people will still not change their minds.
Latimer,
Nullius has clearly explained it. The explanation had to be simplified, because there are many local complexities (day/night, clouds, rotating planet, storage sited like the oceans, long period cycles, etc.), but his (and my) explanation is the basics, and correct. He is also correct saying that people on both sides of the issue get it basically wrong most of the time. When I read over many of the comments I feel I am in grade school, with people with short attention spans.
Well I’m glad that you have spoken and have self-certified that you are completely right. And I’m sorry if some of us are too ill-educated to still have a few questions that we’d like answered. And that you find this an inconvenience.
Strangely enough I was under the impression that this was part of the purpose of this thread..to come up with an explanation of the greenhouse effect accessible to reasonably scientifically literate laymen who are not professional scientists.
Obviously I was mistaken in this understanding … maybe I should go back to ‘grade school’ (whatever that is – is it an American expression?) and work harder on my attention span. Toodle pip
I never see the heat generated in the earth’s core discussed as a parameter for climate modeling, or for accounting in energy equations. Is this because I’ve been unobservant, (and if so can anyone point me to a useful link?) or because the effect of the earth’s own supply of energy upon the atmosphere is generally agreed to be negligible?
I keep coming up with a mental model of an equilibrium-seeking dialogue between two originators of energy – on the one hand a very great one, the sun, separated from the earth’s surface by a great distance, most of it nearly void and (pace the cosmic winds) capable of only one of the 3 forms of heat transfer – radiation – and on other hand a much lesser one, the earth’s core, separated from the earth’s fluid integuments by a smaller distance largely consisting of material capable of conducting and, in its molten phase, conveying heat, but not of radiative transfer.
The “fluid integuments” – ocean and atmosphere, are capable of all three forms of heat transfer but, in the case of radiative transfer, frequency-specific “lacunae” impair this capability, interrupting the energy flux and causing it to reside as sensible heat. The complexity and nonlinearity of the resulting system is owed entirely to its fluid components, of which there are three – ocean, atmosphere and the molten portion of the earth. Yet I see occasional references to submarine vulcanism, a lot more to supermarine vulcanism, but not to other ways in which the earth’s core’s energy product is delivered to the surface. So my mental model has a missing pole, as it were.
I’m sure this is a naive model, but I hope it is sufficiently coherent for me to ask the question above?
It’s not a bad question, just an energy source term that is many orders of magnitude smaller than the incoming stellar energy, and even an order of magnitude smaller than the forcing terms we talk about with respect to climate change. This isn’t true on the outer planets but once a solid crust forms, the flow of heat from the interior of the Earth to the surface is really insignificant (heat diffuses very slowly through solid rock). For example, this source puts it at ~0.075 W/m2. Pollack et al 1993 did a study of this over about 20,000 sites and found a similar value. Actually, even Fourier came to this realization in his early work.
Corrected Pollack link
http://www.agu.org/journals/ABS/1993/93RG01249.shtml
He did a study of sites on land where the crust is much thicker than the seabed and the temperature differential is lower. Also, there are many more active volcanic vents on the seabed than on the land surface, and we know little of their energy output variability.
Not saying this is a principle cause, but needs further investigation.
Another good explanation here http://www.skepticalscience.com/Stratospheric-Cooling-and-Tropospheric-Warming.html
Consider the polar night, no sunlight. Conditions become statically stable (little to no turbulence, absolutely no convenction). Radiation and horizontal advection are the only things operating. The temperature profile is much closer to isothermal, no sign of dry or saturated adiabatic lapse rates.
See Curry 1983 (this was actually part of my Ph.D. thesis) to understand how the atmospheric temperature profile and the surface temperature evolve under these conditions. In fact i ignore horizontal advection, so this is just pure infrared radiation. It would be really interesting to rerun these experiments using doubled CO2 (which I unfortunately don’t have the time to do.)
For some observed wintertime profiles in the arctic, go to the University of Wyoming atmospheric soundings site, click on PABR (Barrow, Alaska) (for type of plot I suggest GIF: Stuve), the current surface temperature is about -25C, and the tropospheric temperature is about -55C. This is a relatively boring wintertime sounding (and it isn’t real cold yet). Click on YRB, Resolute, you see the temperature profile at 800 mb is warmer than the surface, but overall close to isothermal. Check out Cambridge Bay (YCB), the temperature at 650 mb is the same as the surface temperature. Note, these are early winter temperature profiles, gets much more interesting in January (and even more interesting in Siberia). Often the vertical profiles get very jagged and irregular, arising from horizontal advection and residuals from previous cloud layers, but these profiles are pretty smooth and look to be dominated by IR.
So these cases represent pure greenhouse effect (infrared radiative transfer) in action.
“It would be really interesting to rerun these experiments using doubled CO2 (which I unfortunately don’t have the time to do.)”
Well there might be people, who find the time. It looks like stuff, Fraedrich and Lucarini and others in their vicinity should be interested in.
If you wish to see the effect of CO2 increase in the near polar cases, be sure to use the local insolation rather than the global average. In winter I suspect the Solar insolation is so low (near zero at the poles) that the entire atmosphere and ground would be much colder unless horizontal advection replaced the lost energy. An isothermal (or even inverted) lapse rate would mainly be due to lost ground radiation through the long wave “window”, without solar replacement heating
Judith
Your link to the University of Wyoming atmospheric sounding page site is broken.
I was able to track down their site. I wrote this post about how to generate your own DIY temperature sounding profile for citizen scientist.
Apologies for not having read all the comments on this, so this may have been said already :-
Judith, you say “these arguments refuting atmospheric warming by CO2 are being made by scientists that take themselves seriously on this issue” and things like “The G&T paper has been rebutted by Halpern“.
You talk about a rebuttal as if it disproved the paper it rebuts. Well, the way I understand science, it doesn’t. It is perfectly normal for scientists to put up opposing positions, and for the disagreement to continue for years. How do these disagreements get resolved? In the end only the actual science – ie. the evidence – can do it. You have to keep going back to the underlying science until incontrovertible evidence has built up.
And even then new evidence can show up that overturns it again…..
I don’t take issue with mainstream physics on the basic effect, understanding it roughly, enough to sort of “park” there, still ready to move away if needed.
To the extent I see it as provisional, it’s more with the on-lookers curiosity as to what modellers may need to do in order to accomodate proxies/geo-sciences and solar-cosmos-science empiricism if necessary.
Still I’m not sure any of these known listed physics-maverick opinions would be vindicated necessarily by whatever that might turn out to be. Parts of someone’s perhaps. Also not about basic-physics-explanations as being key to what overall listening to skeptics should amount to. But this I get it will come later.
There is even still some confusion around about the so common acronym AGW, whether it means any part or most of the modern warming coming from raised CO2.
Sorry, heretic not maverick was the word I meant to write there.
Tallbloke, I am trying to think of other ways to explain the ocean heating issue.
Take a single column ocean mixed layer model (I recommend Clayson’s model that includes the details of the skin layer also) http://journals.ametsoc.org/doi/pdf/10.1175/1520-0442%282002%29015%3C1805%3ASOACSC%3E2.0.CO%3B2
Force the model with observed solar radiation; surface air (10 m) wind, air temperature, humidity (the model calculates the sensible and latent heat flux). Then run two experiments where you use the observe downwelling infrared radiation flux, and then you perturb the downwelling IR flux for more and less CO2.
If I am correct, then the surface temperature and upper ocean heat content will warm/cool by adding/subracting CO2 (more/less downwelling IR). If you are correct, the surface temperature will remain unchanged since the IR heating simply causes increased evaporation and latent heat flux. Again, I do not have time to do this (I am already way overstretched by this blog), but I am highly confident of the answer based upon all of the simulations using the mixed layer model that Clayson did in her Ph.D. thesis (I am her advisor). I realize that this is an appeal to experience and inside info, but all I have time for. But this is testable.
Re your idea that that increased surface heating results in increased evaporative/latent heat flux. The latent heat flux is driven by surface wind and the difference between atmospheric surface specific humidity and saturation specific humidity of the ocean surface (which is a function of the skin surface temperature). There is no particularly direct relationship between surface temperature and latent heat flux, and latent heat flux is driven more by wind and atmospheric humidity. Take a look at some global climatologies of ocean surface latent heat flux.
http://coaps.fsu.edu/scatterometry/meeting/docs/2008/oceanography/grodsky.pdf
The largest values are actually over the western boundary currents like the Gulf Stream. Instantaneous (daily) maps show that storms dominate the latent heat fluxes.
So here are some ways to test your ideas. Based upon my background knowledge (which is quite extensive in this particular area), I don’t think your idea on this is correct. Like I said previously, unfortunately I don’t have time to do the calculations.
I have a couple of questions on that.
1. Do you remember what value or values of the ratio of ocean heating by SW vs LW?
2. You mentioned models. Has any of that been confirmed by ARGO floats or other real measurements? And on ARGO floats, I keep reading that the raw data isn’t published. Is that true and, if so, why?
The Kantha and Clayson ocean mixed layer model has been validated extensively by observations, including research quality observations conducted during ship campaigns. It is the best one on the “market.”
Re the ratio of SW to LW, that depends on the location. The KC model has been applied extensively in tropical latitudes (high SW) and high (north) latitudes (low SW).
If you want more documentation on this, let me know and I will provide further refs.
Regarding the ARGO floats, I don’t know anything about the details of this situation. I agree that the raw data should be made available, along with clear documentation of the processing that went into the processed version.
I can’t get to it until the weekend, but I would be interested in more information on the model. I can’t afford to get papers behind paywalls, so it that is the case, just say so and I’ll move along.
Oh my, everything is behind paywall. Kantha and Clayson have written two textbooks. The only paper not behind paywall is one on my web site:
http://curry.eas.gatech.edu/currydoc/Webster_JC9.pdf
Anyone who has a serious interest in these papers (or any others that i mention) and you don’t have free access to them, send me an email and i will email a copy to you.
Seamen tell us vast areas of ocean around the tropics (about 8deg north and south from memory) are called “the Doldrums” because the seas are usually very light with little or no wind.
This would confirm the KC model would it not?
Judith, thanks for this more detailed response.
I’m surprised the ‘experiment’ you propose hasn’t been done already. Would it be appropriate to contact Carol Anne Clayson to ask?
My knowledge and ideas are evolving as I deepen my study into oceanology. Of primary interest to me is that the reduction in humidity since 1948 as measured by radiosonde balloons may well have offset any increase in radiative flux from co2. Miskolczi’s work with HARTCODE, leaving aside his ‘saturated greenhouse’ theory confirms this. This renders the co2 perturbation moot in the real atmosphere it seems to me, and I don’t understand why the radiosonde measurements are ignored by mainstream climate science. They can’t be all that bad, or the interesting correlation betwen specific humidity at the 300mb level and solar activity I discovered wouldn’t have such a good fit.
The question then becomes, “what caused the warming?”. The obvious answer is the Sun, and the reduced albedo empirically measured by the ISCCP cloud project. It is much easier for the sun’s shortwave radiation to warm the ocean than it is for downwelling longwave radiation.
At night, when there is no shortwave, the skin temperature is 0.3C lower than the subsurface according to theory. (See Science of Doom’s latest post in comments http://scienceofdoom.com/2010/12/05/does-back-radiation-heat-the-ocean-part-three/#comment-8003 ) Doesn’t this indicate which way the flow of energy is going? He quotes extensively from Kawai and Wada 2007.
Tallbloke, think of this, get rid of all the CO2, what will happen to the ocean temperature then? will it stay the same, with reduced surface evaporation? Nope, it will cool.
Re the skin temperature, i discussed this at length in my original reply to you. I agree that running some experiments with kantha-clayson ocean mixed layer model would help demonstrate this to you, but clayson is swamped and we pretty much already know the answer based the sensitivity studies that have already been conducted using the model.
Explaining the warming in the ocean for the past 50 years is one issue; there could be multiple causes. Saying that adding more CO2 to the atmosphere won’t warm the ocean is altogether another issue. So it seems that you are conflating two issues here.
Judith,
thanks for the followup reply. The effect of co2 in the atmosphere is logarithmic. Remove all of it, and it will for sure affect the altitude at which the majority of radiation to space occurs. However, what I have been saying is that the increased ‘back radiation’ from post industrialisation co2 level increase isn’t going to cause the ocean to cool more slowly to any significant degree. I’m not saying there will be zero effect, I’m saying it won’t account for the 0.15C the top 1000m of the ocean must have warmed in the 1993-2003 decade to account for the steric component of sea level rise measured by satellite altimetry after the estimated melt volume and other minor factors are subtracted out. The figure I got for that was more in accord with the sort of ocean heat content figures Levitus et al were proposing in 2000 from XBT readings. The figures from Levitus et al 2007 and other oceanography teams are inconsistent with the satellite altimetry. I suspect they may have been fudged to bring the surface forcing into line with the 1.7W/m^2 co2 forcing promulgated by the IPCC and to sideline the solar contribution. Maybe you can shed some light on the issue?
Judith,
I have noticed not a single person has addressed the oceans salinity changes.
http://www.whoi.edu/page.do?cid=897&pid=12455&tid=282
This is not caused by AGW but by pressure as the changes are on the oceans surface.
It would effect how much solar radiation penetration in the oceans and change the surface reflecting of solar energy.
Through known experimentation, this process is impossible through the evaporation process as ALL the salt would be effect and not just the surface salt.
I am having trouble with the “nesting” of replies. PDA on November 30, 2010 at 8:32 pm | writes “Likewise, the effect on mean global temperatures of a doubling in carbon dioxide concentrations in the atmosphere is a physical property that cannot be measured. It can, however, be estimated. I’d say that the accuracy is roughly commensurate with that of geology at the same stage of development.”
Fair enough. Would you give me the logic as to how you arrive at the accuray with which the estimate of rise of global temperatures as a result of doubling CO2, without feedbacks, has been made. If you have no experimental data, how on earth can you estimate how accurate the number is? How do you know that the way the estimate has been made does not have unknown factors which make the estimate just plain wrong? I am sorry, but William Thompson cannot be excluded from this discussion.
The real atmosphere has feedbacks. The concept of otherwise real atmosphere but no feedbacks is an artificial construct, which can be defined in many different ways by choosing which physical effects are included as feedbacks and which in the no-feedback part.
Because it is an artifical concept its users can choose the definition. It is defined in such a way that calculation is based on known physical principles well understood and reliable. All the significant uncertainties are put into the feedbacks.
This approach is perfectly legitimate and may be useful. This chain has indicated clearly that there are many different ways of interpreting the same knowledge on this no-feedback atmosphere. I am not the only one involved in an argument while possibly agreeing fully on the final result of the calculation. In these cases the argument concerns the way of interpreting the logic of the calculation: What is cause and what effect or how the physical effects should be presented to make them understandable to as many as possible?
Pekka Pirila writes “Because it is an artifical concept its users can choose the definition. It is defined in such a way that calculation is based on known physical principles well understood and reliable. All the significant uncertainties are put into the feedbacks.”
I have never read such a load of scientific nonsense in my life. I thought this was Judith Curry’s blog where we talked proper science.
Judith,
Question?
If CO2 is the cause of the “greenhouse effect”, why are we currently having record breaking low temperatures in Canada and Europe?
Joe – ‘cos measurements of temperature over small time periods (days, months, years) are weather, not climate. Climate trends should be looked at over at least 30 year periods
Louise,
If the planet was warming, then we should NOT be having any record lows at all.
Joe,
That’s a complete misunderstanding of AGW.
There is no basis for your assertion. If you can find any research suggesting this, than please share it.
Joe – imagine three groups of children:
100 6 year olds
100 7 year olds
100 14 year olds
(all of these children share the same day of the year they were born).
It is very likely that the average height of the six year olds is less than that of the seven year olds but it is also very likely that some of the six year olds will be taller than some of the seven year olds. However, it is also very unlikely that there will be any six year olds that are taller than any of the fourteen year olds (but not impossible).
In the same way, an occasional record low (and I’m not aware of any recently) does not disprove global warming.
Or alternativelyl – we know that the population is getting taller, therefore there should be no very short individuals?
Joe,
The high/low distraction does not prove or disprove AGW.
Including time period of thirty years.
The warming claimed for CO2 is way less than 1 deg C over the whole 20thC. Record lows and highs are at individual points, where temperatures go up and down by many degrees from year to year. Over a long period of time, one could expect (if the AGW hypothesis is correct) the frequency of record low temperatures to decline slightly, and of record high temperatures to increase slightly. Regardless, both will likely continue to occur for many years yet.
And talking of “long period of time”, don’t take the 30-year suggestion seriously. Given that the Pacific oscillation (PDO) has been taking about 60 years for a complete cycle, and has taken 100+ years in the past, a 30-year period is totally inadequate for most climate considerations. In fact, it has the potential to be the most misleading period that you could possibly select (witness the last 30 years of the 20thC).
If I understand it correcly the basic explanation is that incoming short wavelength radiation penetrates the CO2 in the atmosphere while outgoing long wavelength radiation gets blocked by the CO2.
However clouds (and water vapour) also have a significant affect on both the incoming and the outgoing radiation.
Regarding ModelE climate experiment simulations I have read that ; “there is really nothing that is being assumed about cloud and water vapor feedbacks, other than clouds and water vapor behave according to established physics.” Andy Lacis
http://pielkeclimatesci.wordpress.com/2010/11/23/atmospheric-co2-thermostat-continued-dialog-by-andy-lacis/
I’m sorry to go all technical but can a turbulence model be described as established physics? Can an empiricial model for wall heat transfer be described as established physics? I have a strong feeling that all the elements understood within the term “established physics” are in fact subject to large amounts of uncertainty.
I think it is fair to say that cloud behaviour is certainly not fully understood and is linked to many things including turbulence.
Because turbulence is involved does this mean that all cloud effects can disregarded as merely fluctuations around a mean value set by the CO2 concentration? This seems a somewhat gross oversimplification.
“Tennekes, more than any other individual, challenged the models that climate scientists were constructing, saying models could never replicate the complexity of the real world. ”
http://www.nationalpost.com/story.html?id=9bc9a7c6-2729-4d07-9629-807f1dee479f&k=0
I know this reply isn’t specifically scientific but I do feel that it relates directly to the premise of this post ie: that you feel it is important to explain the mechanics of the so-called “Greenhouse Effect” to as wide an audience as possible and to explain the confidence in said mechanics in the face of alternative explanations.
Honestly, I think the “Greenhouse Effect” is a premise that is (almost) universally accepted by science and layman alike. As one of the latter – at least in terms of science – I’m aware of the ‘nuance’ that seems to exist between atmospheric physicists and Engineers – especially in relation to the 2nd Law of Thermodynamics – on this subject, but philosophically this is not an argument that is even necessary to the debate concerning the the main area of contention in the AGW debate, even amongst scientists, I would contend.
It is possible, for instance, to argue that space time is essentially “flat” and that “curvature”, even spheres, whilst perceptually the way we interpret our universe are perhaps a more of an interpretational anomaly we see and measure simply because of our limited three dimensional senses. However interesting these concepts are – and I think they’re fascinating! – I, along with most people, am quite happy to discuss the future of space exploration, accepting that the World – and other celestial bodies are spherical. Every logical argument requires a premise of some sort!
In a similar way, it is quite possible – and perfectly acceptable I believe – for any relatively informed and critically equipped person to both understand and discuss the evidence for positive feedback mechanisms within the climate system, or the possibility of external cosmic radiation affecting reflective cloud cover, or albedo, or enso, or the effects of phytoplankton on CO2, or any other variable within our climate which may have a bearing on the relative “temperature” of our planet…..without any deeper understanding of the primary “Greenhouse Effect” than the same broad acceptance that the work of Galileo enjoys within Astronomy. The fact that a lack of intimate understanding of the primary physics of CO2 doesn’t preclude an informed opinion within this debate is often – quite deliberately in my opinion – obfuscated by those who try to exclude those without a physics degree from the discussion.
In short, I’m quite happy to accept the premise of the “Greenhouse Effect” and move on.
@Saaad
‘I think the “Greenhouse Effect” is a premise that is (almost) universally accepted by science and layman alike’
Prior to this thread, even I, buried deep in my lair at Sceptic Central (*), would probably have agreed with you.
But the more people begin to argue about it, the less it seems is actually understood. I don’t believe in ‘consensus’ as being a valid way of making scientific progress, but I am aghast that 100 years after Arrhenius the mechanisms of the effect can still not be clearly and unambiguously described.
And yet it is the absolute bedrock of all ‘warming theory’. It is the only game in town. All other things have been eliminated so the only possible thing that can explain warming is the ‘greenhouse’ effect because of CO2. Or so we have been told for over thirty years. TINA – There Is No Alternative.
One of the common errors causing planes to crash is that when an in-flight emergency occurs the crew get too busy doing their own little bit of emergency handling (eg radio, engines, navigation etc) that they are distracted. The crash does not occur because of the emergency but because everybody forgot to fly the the d…d aircraft.
Can it be that for the last hundred years, belief in the greenhouse theory has been so prevalent that everyone has taken it as read. But nobody was actually flying it? It begins to look a little like it.
(*) No – there isn’t really a place called Sceptic Central, and I am not buried in it. It is a figure of speech. I am actually in Surrey in my study watching the snow come down and worrying about how to pay (not be paid by) Big Gas when the winter bill comes through the door. Do not leap to unwarranted conclusions.
I take your point Latimer. I was not meaning to imply blind acceptance of the premise of GHG theory as per Arrhenius. Rather, I was suggesting that to have a meaningful debate about the current perceived points of “uncertainty” within the science at the policy end of things, we must at least allow for some sort of agreed premise from which to proceed. Despite the many threads of discussion above, I still think Arrhenius is a sound first principle, even accepting your caveats.
Between this thread and the post by climatologist Dr. Nielsen-Gammon over at his Climate Abyss blog, my acceptance of the greenhouse effect is substantially reduced as well. It is also interesting that, like the melting glaciers and the very name of the crisis, when pressed hard by skeptics, it turns out that things climate have been mis-named, mis-represented or over hyped. This list is growing, is only growing under skeptical pressure, and is significant: it deals with the basic claims of the AGW community.
What else needs to be closely scrutinized?
hunter his post says nothing. I’d read some more basic texts first.
Steven,
I have come to respect Dr. N-G quite a bit over the two years or so I have been reading him.
I am not certain how you can say he said ‘nothing’. The two posts on what he calls the Tyndall effect seem like good primers and help get past the (mis)use of greenhouse.
Alan Siddons writes in ‘Slaying the Dragon’ that the sun nevers sets in the climate models. Is this true?
??? each location has the appropriate diurnal cycle, but the sun is always shining somewhere on earth.
That is true, but,
What Alan has claimed in the book is: If we take a point source (sun) and shine it on the sphere (earth), half of it is recieving energy at a given point. This energy is simply divided by 4 and spread out over the entire sphere (the earth) in the models.
To quote:
“It is important to understand that radiant energy models don’t deal with sun and earth conditions as they actually exist. If a somewhat realistic model were used, the earth would naturally be hottest at the noon equator, coldest at the poles, but beyond that what – wouldn’t it be close to absolute zero on the shadow side?
Such a problem is hard to solve, especially considering that the earth also rotates, thereby adding the complication of exposure duration vs heat-retention. Modelers therefore find it much easier to avoid these difficulties by imagining that sunlight has equal strength all over the planet. They do this by diminishing sunlight’s power to a quarter of its actual value.
…
342 is what a modeler takes as the energy impingin on every square meter of the planet at once.
All at once. Keep that in mind. Like the summer sun in the Arctic, a modeler’s sun never sets”
This is only a small excerpt from a sample chapter. Siddons develops his concepts further.
I just wanted clarification on this little point about radiant energy models.
Ohmigod! This insight by Siddons will pretty much mean that the coffin of CAGW no longer even exists – it’s nothing but nails now. Devastating.
How was this egregious blunder overlooked for so long?
I’m convinced. “Slay the Dragon” is now on my must read list.
Sounds like he read the blogs on how to calculate T=255K using the solar constant divided by 4 and got confused about what a climate model means versus back of the envelope calculations. I don’t think he even knows why you’d have to divide by 4.
This is completely incorrect. Siddons is talking about simple energy balance climate models (the stuff where you estimate the equivalent black body temperature). This has nothing to do with how all this is treated in numerical global climate models.
Like I said, Dr C, Siddons does not tell that this is how the sun in ‘modeled’ in GCMs. (only in ‘radiant energy models’).
The chapter title is “The weakness of a constant irradiance model’. He cites Kiehl-Trenberth as an example of this kind of model and points out one of its weakness, derived starting from the passage quoted above.
Sounds like he is channelling G&T.
So,
Is this how the earth is heated in radiant energy models? Is Alan Siddons correct in saying this?
I’m not an expert, but ….
“Earth is heated by a sun that never sets in radiant energy models …” sounds like a bad and erroneous way of stating that K&T energy budget diagrams try to match the average incoming energy to the average outgoing energy at equilibrium and that the average incoming heat flux amounts to a quarter of the solar constant. In any case, the phraseology of somebody who states that the night side of the planet should be at absolute zero is not worth analyzing at depth.
This is quite interesting.
You havent even read what Siddons wrote and yet you, and others too, have managed to say funny things.
“Tyndall needed no equations, but only simple logic, to see what many since him overlooked: it is at night that the gases are most important in blocking heat radiation from escape, so it is night-time temperatures that the greenhouse effect raises the most.”
From aip.org
Shub,
Nobody is arguing that the greenhouse effect raises night temperatures – it is the reason why day/night swings on the moon are 250 degrees and much smaller on earth, I don’t know why you are posting this. But one can still look at the heat flux averaged over day and night and argue for it to be conserved. Let’s put this another way. Assume that you have a resistor in parallel with a capacitor. Let’s assume that you have a current source that pulses on and off periodically with exactly the same “ON” and “OFF” time over each period. As you increase the value of the resistor, the voltage swings on the capacitor become smaller. But if you were to average the incoming current, it would be exactly equal to the mean voltage across the capacitor divided by the value of the resistor. In other words, the average is conserved whether or not you assume that the incoming current source was a pulsing source or whether it was a current source that was always “ON” with a value equal to the average current over the averaging period. For the earth system, the sun’s heat flux is equivalent to the current source for the electrical system.
Tyndall followed with rich Victorian prose, arguing that water vapor “is a blanket more necessary to the vegetable life of England than clothing is to man. Remove for a single summer-night the aqueous vapour from the air… and the sun would rise upon an island held fast in the iron grip of frost.”
from aip.org
In summa,
Please read what Siddons has to say, instead of just going after the excerpts I quoted, quite bereft of their context.
Is this meant serious? I honestly can’t tell. Do you honestly believe this?
But Curryja,
Haven’t you herd of people being told to stick their head where the Sun doesn’t shine? (Please excuse, I couldn’t help this).
Not sure what he means by the sun not setting.
SUBROUTINE DAILY(end_of_day) 3,9
!@sum DAILY performs daily tasks at end-of-day and maybe at (re)starts
!@auth Original Development Team
!@ver 1.0
!@calls constant:orbit, calc_ampk, getdte
USE MODEL_COM, only : im,jm,lm,ls1,ptop,psf,p,q
* ,itime,itimei,iyear1,nday,jdpery,jdendofm
* ,jyear,jmon,jday,jdate,jhour,aMON,aMONTH,ftype
USE GEOM, only : areag,dxyp,imaxj
USE DYNAMICS, only : byAM
USE RADPAR, only : ghgam,ghgyr2,ghgyr1
USE RADNCB, only : RSDIST,COSD,SIND, dh2o,H2ObyCH4,ghg_yr,
* omegt,obliq,eccn
USE DAGCOM, only : aj,j_h2och4
IMPLICIT NONE
REAL*8 DELTAP,PBAR,SPRESS,SMASS,LAM,xCH4
INTEGER i,j,l,iy
LOGICAL, INTENT(IN) :: end_of_day
C**** Tasks to be done at end of day and at each start or restart
C****
C**** CALCULATE THE DAILY CALENDAR
C****
call getdte(Itime,Nday,iyear1,Jyear,Jmon,Jday,Jdate,Jhour,amon)
C**** CALCULATE SOLAR ANGLES AND ORBIT POSITION
C**** This is for noon (GMT) for new day.
CALL ORBIT (OBLIQ,ECCN,OMEGT,REAL(JDAY,KIND=8)-.5,RSDIST,
* SIND,COSD,LAM)
Judith:
This is a good resource:
http://maths.ucd.ie/met/msc/PhysMet/PhysMetLectNotes.pdf
a fairly lucid description of the “greenhouse” effect.
Te is known as the effective emission temperature. It is determined solely by the insolation and the planetary albedo. On Earth, Te is much colder than the observed global-mean surface temperature of 15◦ C or 288 K. The difference must be due to the atmosphere. The warming effect of the atmosphere, known as the greenhouse effect, is best understood as
follows. The atmosphere is opaque in the infrared, which means that the mean emission level is lifted off the ground. The mean temperature at the emission level (i.e. the mean brightness temperature) must be Te in order for emission to match absorbed insolation. But the atmosphere has a positive lapse rate, and so the temperature at the ground must be
greater than Te .
In general, an atmosphere must satisfy 2 conditions in order to provide a greenhouse effect: it must absorb radiation radiation in the spectral range associated with black body radiation at temperature Te , and it must have a positive lapse rate. An atmosphere with a negative
lapse rate (temperature increasing with height) will have a surface temperature colder than Te . This in known as the anti-greenhouse effect, and actually occurs on Earth in the polar regions during winter, as evidenced by Fig. 5.17b.
Basically, the very first step is to get people to recognize and accpet that the earth is warmer than it would be with no atmosphere.
Steve,
Did you not read the very clear discussion by Nullius in Verba Nov 30 at 3:13 pm, and my similar but less well stated version on Nov 30 at 6:30 pm (this is out of order as it was a reply). I also gave links to more detailed discussions (including mine) at Nov 30 10:46 am.
These all clearly state what you are trying to say.
no, I read from the bottom up
Dr Curry,
Thank you again for putting up with this blog. While obviously a burden to keep up, it is a wonderful resource for those of us who are trying to get a better grasp of the relevant factors, It is a public service of the best kind.
One housekeeping item.
The very wide margins that are used in this blog make it more difficult to follow the thread of a discussion. This topic for instance when cut and pasted into Word takes 123 pages. Would it be possible to change the format to something akin to that used in Climate Audit, so that the full width of the page is employed?
For what it’s worth, I’ve got my illustrated explanation of the Tyndall gas effect (more generally sort of known as the greenhouse effect) written up and posted. Since I divided my time today between helping students and writing this entry, some of this may be redundant, but oh well.
i like it (unfortunately i’m not your target audience), lets see what the reaction is.
I’m not sure if I’m a “target,” but I like the “Tyndall gas effect” better than greenhouse gas or greenhouse effect.
I hesitate to consider myself a ‘target’ for Dr. N=G, since he lives in Texas and I have questioned him on more than a few occasions. ;^) But his two posts on what should now be called the ‘Tyndall Gas Effect’ are very good primers and clear up the difference between what is happening in the atmosphere and a greenhouse. And since I am probably a good example of a non-scientist interested in climate and other science issues, I guess I am a target. Should I duck?
Judith,
You say :- “However, whether atmospheric gases such as CO2 (and H20, CH4, and others) warm the planet is not an issue where skepticism is plausible.”
It seems to me that, within certain limits, skepticism of this statement is perfectly plausible. I tend to agree that a doubling of CO2 would likely cause a small increase in temperature, if all else is perfectly unchanged. But, a doubling of CO2 should cause other changes, relating to plant growth, transpiration, evaporation, clouds, animal growth, etc, etc.
Why is it so plausible or logical to consider some sort of false future where CO2 is increased, but all else remains exacly the same? Isn’t it plausible that an increase in CO2 may possibly cause a small change in atmosheric water vapour, or clouds, which couteracts the theoretical laboratory effect of CO2 increase on temperature ?
Peter, your statement goes far beyond what I said, into the realm of feedbacks. I will have a series on sensitivity and feedbacks, starting hopefully before the end of the month.
For a primer on feedbacks that I wrote while you wait for Judith, see
http://www.realclimate.org/index.php/archives/2010/09/introduction-to-feedbacks/
And Part 2, a bit more advanced
http://www.realclimate.org/index.php/archives/2010/11/more-on-feedbacks/
Thanks Chris
How about the Martian galactic rays too?
:-)
Physics of the atmospheric greenhouse effect: What exactly is the question mark about?
Some have complained that the greenhouse effect is inappropriately named. But they don’t insist that a butterfly be named something else, given that it is neither a fly, nor is it made of butter. English is English for whatever that is worth. You arrive at the words and their conventional meanings because the words get defined by those who use them.
But “serious” arguments against the (greenhouse) theory by the likes of
Gerlich and Tscheuschner, Claes Johnson, and Miskolczi? Perhaps the word “serious” was meant to suggest that the authors of these papers were being sincere in what they were writing, and therefore “serious”.
I could also entertain the possibility that they might be writing their stuff as a “spoof”, just to see who might be taken in. You use equations, make the language sound authoritative by including the right shop talk and buzz words, then come up with some outrageous conclusion. I have seen this happen before in the social sciences,winding up on the Op-Ed pages of the New York Times.
Actually, the Gerlich and Tscheuschner, Claes Johnson, and Miskolczi papers are a good test to evaluate one’s understanding of radiative transfer. If you looked through these papers and did not immediately realize that they were nonsense, then it is very likely that you are simply not up to speed on radiative transfer. You should then go and check the Georgia Tech’s radiative transfer course that was recommended by Judy, or check the discussion of the greenhouse effect on Real Climate or Chris Colose science blogs.
The technical books by Goody and Yung, Thomas and Stamnese, and Liou are a bit heavy going. I would recommend the more readable paperback text by Grant Petty (A First Course in Atmospheric Radiation, available from sundog publishing for $36). It does not answer all questions, but does have a lot of good and useful material.
If the authors Gerlich and Tscheuschner, Claes Johnson, and Miskolczi are not “spoofing”, then I am rather curious about their thought processes as to just how it is that they arrive at such erroneous conclusions. Did they bother to check their results against the published literature? Radiative transfer has been around for a long time, so there are thousands of relevant papers to compare their results against. If they found differences with published results, they should have checked to see what errors they may have made. Perhaps it is that they somehow feel that they have arrived at some new understanding that has been missed by everybody else.
The notion by Gerlich and Tscheuschner that the second law of thermodynamics forbids the operation of a greenhouse effect is nonsense. The notion by Claes Johnson that “backradiation is unphysical because it is unstable and serves no role” is beyond bizarre. A versatile LW spectrometer used at the DoE ARM site in Oklahoma sees downwelling “backradiation” (water vapor lines in emission) when pointed upward. When looking downward from an airplane it sees upwelling thermal radiation (water vapor lines in absorption). When looking horizontally it sees a continuum spectrum since the water vapor and background light source are both at the same temperature. Miskolczi, on the other hand, acknowledges and includes downwelling backradiation in his calculations, but he then goes and imposes an unphysical constraint to maintain a constant atmospheric optical depth such that if CO2 increases water vapor must decrease, a constraint that is not supported by observations.
A useful starting point to get a better feel for how thermal radiation works is to consider the classical isothermal cavity maintained at a fixed temperature T. Radiation emitted through a small pinhole from this cavity is always going to be isotropic Planck radiation at temperature T whether the cavity is empty, or if there is absorbing or reflecting material within the cavity. From this concept, it is straightforward to develop equations for how much an absorbing layer within the cavity of specified optical depth and temperature T will emit, since the sum of the layers emission and transmission must be equal to the Planck radiation coming through the pinhole. The same emission and transmission equations apply for the absorbing layer in question if removed from the isothermal cavity and placed in atmospheric context that is in local thermodynamic equilibrium.
Mr Lacis, I take issue with your 2nd paragraph only.
True, that insect is neither a fly nor made of butter. Nor is a pineapple an apple or the fruit of a pine tree. However, being thus named has no consequences on geopolitics or global economies.
The average person in the street who isn’t interested in studying the science hears the term “Greenhouse”, recalls their knowledge of or visit to a botanical greenhouse and says “yeah, it gets bloody hot in those places”. And coupled with statements such as “we can’t keep pumping this POLLUTION into the atmosphere” decides that there IS a problem and reflects this at the polling booth. (Recent elections in OZ with substantial increases in Green party support).
Words are bullets, especially in a field like science. I for one expect, nay demand, true and accurate descriptors.
And when very very highly educated people shortcut their descriptors, I want to know whats on their agenda. I want to know if they are impartial seekers of truth or advocates.
No, The Greenhouse Effect is not a good descriptor. I know what makes a marketgardeners greenhouse hot and it ain’t CO2.
…..”The notion by Gerlich and Tscheuschner that the second law of thermodynamics forbids the operation of a greenhouse effect is nonsense.”…
In their paper G&T make clear that only some of the “greenhouse theories” fall foul of the second law.
Some other fall foul of the first law and multiple other mistakes.
In fact one of G&Ts complaints is they cannot find a version of the “Orthodox Greenhouse Theory”.
You have recommended a number of textbooks relating to climate physics.
Do these text books (and in general UG courses in climate science) include the Carnot Cycle and the Second Law of Thermodynamics?
I’m certainly not “spoofing” when I say that Ive found an incredible ignorance about the direction of heat flow in the atmosphere amongst supporters of the IPCC position .
Statements such as “backradiation heating the Ocean” are not hard to find.
Bryan, FYI, basic thermodynamics is part of the undergraduate curriculum in climate science (and in the earth and atmospheric science departments that teach climate science.) I have written a textbook on Thermodynamics of Atmospheres and Oceans, and there are about a half dozen similar texts on the market. Most meteorology and atmospheric science departments teach a full course in thermodynamics (applied to the atmosphere) at the undergraduate level, which is a required course in the curriculum.
Thanks for the reply.
I’m reassured that thermodynamics is being taught.
However I asked specifically about the Carnot Cycle.
It forms the core of analysis into heat engines and refrigerators.
Its conceivable that since neither are found naturally in the atmosphere that it might be omitted.
However this would be a mistake as it also is also the introduction to analysis of the Second Law.
I have come across a number of proponents of IPCC position who have interpreted the Second Law as;
“its alright for heat to flow from low to higher temperature as long as more heat flows from high to low temperatures at the same time.”
Which of course is wrong.
I used to agree with you, that the name is not important. But when the AGW community has a pattern of shifting names under pressure and also indulges in the entire ‘denialist’ and ‘conspiracy’ schtick in dealing with skeptical challenges, I think names are a bit more significant than just place markers.
Also, as we watch the list of failed predictions about the global warming crisis grow, it is good to take time to revisit what the AGW community has told us over the years and decades.
A Lacis
I think you have misread Miskolczi. He starts with the data, calculates each of the radiative parameters across an atmosphere 150 layers deep in 9 different directions. He calculates a full Planck weighted optical depth.
From that he fits the data to curves to come up with simplifying relationships. That he turn interprets in light of entropy maximization principles. From what I understand, he does NOT a priori impose “an unphysical constraint to maintain a constant atmospheric optical depth”.
Rather he develops subsequent theory to model and explain the atmosphere behaving effectively in that way to explain the very stable global optical depth actually observed over the last 61 years including all available moisture, temperature and CO2 data.
See my detailed response to your posts in Judith’s best of the greenhouse summary.
See Essenhigh’s thermodynamic model of the atmospheric column
Comment on “unphysical constraint”
comment on order of calculations
I think you read his process backwards – He starts with the data and radiative evaluations, not the simplifying assumptions and entropic explanation. Look forward to your feedback – over at the summary page.
Its good to see more discussion on Miskolczi’s paper. It is not easily understood, and ranks IMO as the one skeptical analysis that is worth some detailed discussion. I’ve read the paper, felt that it didn’t make much sense, but I didn’t spend much time on it.
I have not seen this book discussed
Global Warming and Global Cooling, Volume 5: Evolution of Climate on Earth (Developments in Earth and Environmental Sciences) , O.G. Sorokhtin, Leonid F. Khilyuk Ph.D. Ph.D. , G.V. Chilingarian
http://www.amazon.com/Global-Warming-Cooling-Developments-Environmental/dp/0444528156/ref=sr_1_1?ie=UTF8&s=books&qid=1291223589&sr=1-1
Probably somewhat late to comment.
Nullius in Verba said on November 30, 2010 at 3:13 pm:
A great deal of confusion is caused in this debate by the fact that there are two distinct explanations for the greenhouse effect: one based on that developed by Fourier, Tyndall, etc. which works for purely radiative atmospheres (i.e. no convection), and the radiative-convective explanation developed by Manabe and Wetherald around the 1970s, I think. (It may be earlier, but I don’t know of any other references.)
Climate scientists do know how the basic greenhouse physics works, and they model it using the Manabe and Wetherald approach. But almost universally, when they try to explain it, they all use the purely radiative approach, which is incorrect, misleading, contrary to observation, and results in a variety of inconsistencies when people try to plug real atmospheric physics into a bad model. It is actually internally consistent, and it would happen like that if convection could somehow be prevented, but it isn’t how the real atmosphere works.
1. I would like to comment on “when they try to explain it“.
In atmospheric physics text books and papers on the subject, when climate scientists “try to explain it” the explanation is correct.
Perhaps someone did it incorrectly once, but I haven’t found it yet in any technical publications discussing this subject.
Many websites set up to explain to the general public in media-friendly sound-bites probably do explain it badly. Or non-technically. Or completely wrongly.
But I believe it is important to differentiate between the two worlds.
To criticize how climate scientists describe atmospheric physics based on what NASA or the Met Office explain it via their marketing departments on their public websites seems somehow unfair to me.
Or even to criticize how someone technically competent tries to explain a complex technical subject to a non-technical audience by saying “you made it too simple”.. Equally you could say “you made it too complex”..
Wonderful if Moving on.
2. Another comment that can, and has, caused confusion is the somewhat false dichotomy of “good” vs “bad” explanations of how the “greenhouse” effect works.
The “real mechanism” as Nullius and Leonard Weinstein describe is correct – as more “greenhouse” gases are present, the effective height of radiative cooling to space increases. And because temperature decreases with height due to adiabatic expansion, a higher altitude for this radiation = less radiation = less ability to move heat out of the climate system and therefore = “a heating”.
This explanation is the one you find in the atmospheric physics textbooks, and the papers.
However, the idea that “back radiation” is irrelevant is not really correct. It is essentially a complementary effect.
How is it possible for surface temperatures to increase under this model? Surface fluxes must balance. Yet solar radiation is still the same. A higher surface temperature will cause a higher convective flux and a higher radiative upwards flux. (Increase in energy from the surface).
How is this possible? There must be a balancing surface item. The balancing item is the back radiation. More “greenhouse” gases will cause more downward radiation (lowering effective altitude of downward radiation).
It isn’t one vs the other. One is a consequence of the other. The “controlling mechanism” is the radiative cooling to space which is determined by the effective height of the radiation. Downward surface radiation from the atmosphere increases as a result. All are linked.
(Note these explanations are all prior to any feedbacks).
Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity, by Manabe and Wetherald was published in 1967.
scienceofdoom
Good post and the outlines of a testable proposition emerges.
The consensus of this thread seems to be that as you say;
………” The “real mechanism” as Nullius and Leonard Weinstein describe is correct”……….
However you would like to include the effects of the postulated increased CO2 as increasing the greenhouse effect at near surface lifting the layered structure of the atmosphere up.
If you can supply evidence that the magnitude of the CO2 increase causes energy density at near surface atmosphere to increase correspondingly then you have a case.
The proof would need to be in appropriate units such as Joules per cubic metre rather than a mere assertion.
Bryan,
The adiabatic lapse rate is a gradient not a specific temperature. Thus if the temperature at the “effective” altitude of outgoing radiation that matches the absorbed solar radiation is raised, the ground temperature will increase from the adiabatic lapse rate times altitude plus outgoing gas effective temperature. Near the ground, that higher resulting temperature will result in more radiation from the ground and more back radiation, but the only radiation HEAT transfer is due to the difference of outgoing radiation and back radiation. Thus on the average there is no back radiation HEATING, but there is back and forth energy transfer. Confusion of the difference of energy transfer and heating is the cause of most of this confusion. The increased back and forth radiation is an EFFECT, not cause of the increased heating.
Bryan,
in my sentence “Thus if the temperature at the “effective” altitude of outgoing radiation that matches the absorbed solar radiation is raised, the ground temperature will increase from the adiabatic lapse rate times altitude plus outgoing gas effective temperature”, I meant to say: Thus if the location where the temperature at the “effective” altitude of outgoing radiation that matches the absorbed solar radiation is raised, the ground temperature will increase from the adiabatic lapse rate times altitude plus outgoing gas effective temperature
Leonard
I fully appreciate that the lapse rate is a gradient.
Its no coincidence that the dry lapse rate involves the constant 9.81 the magnitude of the acceleration due to gravity.
The lifting of the tropopause would be because the lapse rate was further reduced by condensation and convection mainly.
However scienceofdoom (if I understand him properly) was proposing that because of increased CO2 we would have a stronger “greenhouse effect” thus increasing surface temperatures.
Increased surface temperatures while not changing the lapse rate would increase the height of the tropopause.
This is because the molecular KE of gases at surface boundary had increased.
Now this is a perfectly rational proposition and further it seems testable.
It seems that an analysis of past records of the height of the tropopause and how it varies with;
1. Surface temperature
2. Humididy
3. CO2 levels in the atmosphere
There are a number of other factors I’m sure.
However it does seem possible that the relevant driving factors could be teased out from data we already hold.
Hi there, scienceofdoom,
We’ve had this discussion before, of course. I still respectfully disagree.
(Respectfully because I’ve learned a great deal from your excellent site.)
“a higher altitude for this radiation = less radiation = less ability to move heat out of the climate system and therefore = “a heating”.”
The ability to move heat out of the climate system is exactly the same, the heat being radiated out of the system is exactly the same: it’s the heat that is being absorbed by the system and is fixed by insolation and albedo. The only difference is that it is at a higher altitude. The higher it is, the thicker the sandwich of air between there and the ground, which when multiplied by the lapse rate gives the surface temperature.
“A higher surface temperature will cause a higher convective flux and a higher radiative upwards flux. (Increase in energy from the surface).”
I’m not entirely sure, but by emphasising the word “from”, I suspect that you’re still making the assumption that convection can only transport heat upwards, never downwards. Convection (in the sense of a bulk air movement induced by temperature differences) can transport heat both ways. “Convection” refers to the entire cycle.
“The “controlling mechanism” is the radiative cooling to space which is determined by the effective height of the radiation.”
The controlling mechanism for the temperature of air at the average emission altitude (the IR-visible ‘surface’ of the planet) is as you say. The controlling mechanism for the temperature at the solid surface of the planet is the altitude of the average emission level, and the lapse rate between that point and the surface.
So long as the temperature profile of the atmosphere is adiabatic, and hence linear, the temperature at any point is related to the temperature at any other point as a simple function of the gradient of the line and the difference in heights and nothing else. Unless the back radiation can affect one or the other of these, it cannot possibly have any effect.
The one part of my model that I have left deliberately vague is the determination of the average emission height, which involves not just the concentrations of the greenhouse gases but their temperature and density profiles. If the level of back radiation affected the tropopause height, say, and hence the thickness of the moist turbulent layer, it could affect the heights of emission from water vapour. Or maybe convection across the full range of altitudes would be impossible without it. But I don’t see any other way for it to have a critical effect. A linear function has only two parameters. dT = MALR*dz. Which of these does back radiation affect?
I like the way scienceofdoom puts it and I think the difference lies in transient versus steady state behavior. I think the point is that if backradiation did not warm up the surface more, you would not have energy balance at the top of the atmosphere and therefore, if you assume a system where you suddenly turned the sun on, you would have less energy leaving the system than was entering it until you reach steady state.
In other words, I believe that the derivation of a constant lapse rate implicitly assumes steady-state behavior i.e. it doesn’t take into account the start-up energy buildup within the earth system to achieve a mean “stored energy” state.
http://en.wikipedia.org/wiki/Lapse_rate
Hot air rises, cold air descends. Which direction is energy transported in each case? I suggest the directions of mass and energy fluxes need not be the same.
Hot/cold relative to what?
Consider a completely transparent atmosphere of pure Nitrogen/Oxygen on a planet with a hot surface at the equator and a cold surface at the poles. Radiation to space all occurs from the surface. The air immediately in contact with the surface is at the same temperature as it by conduction.
What happens? Does it convect?
If it is static, what force keeps the dense cold air at the poles from flowing towards the hot light air at the equator? (And the air at altitude from flowing out towards the poles?) If convecting – rising at the equator and descending at the poles, from which it will be radiated, which way is the heat flowing at the poles? Or does all the air rise and never descend again?
Nullius,
By Wikipedia definitions, I am referring to natural convection while you have proposed a forced convection pump.
The steady-state solution to your posed problem is more than adequately given by thermal conductivity. Gradients are several orders of magnitude below those required for convection. Thermal profiles are isothermal vertically with a slight warming at higher altitudes increasing with latitude. An atmosphere ca. 10Km thick is assumed for an earth-sized planet and rotational effects are ignored.
“Convection” versus”forced convection pump” is a question of differing definitions. I was trying to keep things simple.
I’m interested to know more about your steady state solution. Can you say specifically: what force keeps the dense cold air at the poles from flowing towards the hot light air at the equator? And the air at altitude from flowing out towards the poles?
And what is the gradient required for convection?
Nullius,
Just a back of the envelope calculation. First, visualize a film 1 unit thick and 1000 units long on a level hot plate with a horizontal temperature differential of 100K. With that aspect ratio, the obvious first guess is a uniform vertical temperature. To refine the picture, as you indicate, cooler air of higher density will try to slip under warmer air adjacent, but it will also be warmed by the underlying hotplate and thus we have a competition between thermal and viscous diffusion. The dimensionless Prandtl number, for air about 0.8, indicates these processes are closely matched and consequently horizontal and vertical temperature gradients will be similar. The given surface gradient 10^-2 K/Km, applied vertically, yields a 0.1K vertical temperature difference and a lapse rate well below that needed for turbulence.
Are you saying the force that keeps the cold air from slipping under the warm is viscosity? Or that it does slip under, but then gets warmed up? (i.e. the temperature field is static, but the air is not?)
If the latter, isn’t that a convective cycle rather than a static solution?
I’m saying we’ve discussed a problem equivalent to energy and mass transfer through a capillary layer (L/W = 1000) connecting two reservoirs of different temperatures and ill-defined pressures and for which viscosity limits mass transport.
My ‘research’ indicates that definitions of convection can cover a range from molecular diffusion to turbulence. Personally, I favor a more restrictive definition which would not include capillary flow. If I used the words ‘static solution’, I intended steady-state or stationary.
As to the hypothetical GHG-free planet, I’d first look for solutions involving a thin fluid layer on the surface of a rotating sphere.
Capillary flow? You’re saying that we would have a 10 km thick boundary layer? I think I must be misunderstanding in some fundamental way what you’re intending to say.
Your definition of “capillary” makes no sense to me. The dimensions of the atmosphere (10 km x 10,000 km) are the same whether the atmosphere contains GHGs or not, so if the transparent atmosphere is a capillary layer, then so is Earth’s actual atmosphere. Personally, I’d define ‘capillary’ as one in which capillary forces had a significant effect on the flow. Nor do I understand why you’re restricting the definition of convection. For the purposes of this discussion, it’s the bulk motions of air caused by temperature-induced density changes.
You haven’t said why you think viscosity limits mass transport, and I’m still not clear on whether you think the air would move or not.
If the air is stationary then pressure at the surface must be constant, or there would be unbalanced horizontal forces. Hence the mass of air over each square metre must be the same. If temperatures are different over hot and cold areas, then their densities will be different, and you will need a much taller air column over the hot areas to balance the pressure over the cold areas. But with nothing but the vacuum of space to hold it up, any such column would spill out on top of the cold air, raising the pressure there and inducing circulation. You can’t get the same pressure at the bottom and the same air column height at the top with different densities.
Saying “I’d first look for solutions…” gives the impression that you don’t yet have a solution. (Incidentally, if the air is not moving, then the rotation has no effect.) But you said above “The steady-state solution to your posed problem is more than adequately given by thermal conductivity.” Do you know of a solution or not?
Nullius:
Your last paragraph is crucial. The whole disagreement is removed, when its meaning is properly understood. There are different ways of looking at the same phenomena and they meet in understanding your last paragraph.
OK, I’m a bit of a simpleton, I guess, but I see it this way. The visible radiation from the Sun heats the ground which in turn radiates infrared radiation upwards. Much of this radiation is captured by CO2. This heats the CO2. The pressure in the lower atmosphere is such that the CO2 almost immediately bangs into another molecule and heats it. So the “heat” captured by CO2 rapidly heats the air around it. Now, the only way this cannot heat the atmosphere is if the heat were instantaneously dissipated into space. Since this cannot happen instantaneously, the CO2 in fact heats the atmosphere and causes warming. The details of how this heat gets spread around from this point don’t really matter.
Jim – my understanding is that what you say is absolutely correct, except for”Much of this radiation is captured by CO2”. As I understand it, only one very narrow band of radiation is captured by CO2. There is a serious question, therefore, about the magnitude of the effect. It only matters if it is reasonably large, ie. enough to significantly affect climate. This can be tested : if it is reasonably large then the heat generated as you describe in the tropical troposphere (and see IPCC report AR4 fig. 9.1 panels (c) and (f)) will be measurable. It isn’t (http://onlinelibrary.wiley.com/doi/10.1002/joc.1651/abstract, http://www.pas.rochester.edu/~douglass/papers/addendum_A%20comparison%20of%20tropical%20temperature%20trends%20with%20model_JOC1651%20s1-ln377204795844769-1939656818Hwf-88582685IdV9487614093772047PDF_HI0001).
The effect that you describe therefore has little effect on the global climate.
The first link it to a paper behind a pay wall, the second link doesn’t seem to work. I purposely didn’t quantify much. From the transmission spectra of LW through the atmosphere, it does appear to capture a good deal :) of it.
The paywall is a mystery, as I don’t get past any. Try here:
http://www.nsstc.uah.edu/atmos/christy/2007_Dougless_etal.pdf
There is a later paper here:
http://www.nsstc.uah.edu/atmos/christy/2009_DouglassC_EE.pdf
CO2 transmittance in the infrared spectrum is shown graphically here:
http://webbook.nist.gov/cgi/cbook.cgi?ID=C124389&Units=SI&Type=IR-SPEC&Index=1#IR-SPEC
for comparison, H2O is here:
http://webbook.nist.gov/cgi/cbook.cgi?ID=C7732185&Units=SI&Type=IR-SPEC&Index=1#IR-SPEC
Mike, I was trying to make the simplest point possible, that CO2 will facilitate the heating of the air. If you look at my original argument, it is very difficult to deny. The detail will determine the amount of heating and secondary effects will determine if that heating is amplified or damped. But I don’t believe you can show that my original argument is wrong. It is step 0, if you will.
Jim – I’m not trying to show that your original argument was wrong. As I said in my first reply to you (“Jim – my understanding is that what you say is absolutely correct“), I agree with you. The question is: how significant is the effect (on the existence of which we agree).
Question
1) Does a physical climate model exist, or has anybody built one? I’ve tried to search on Google.
Climate models are not being specifically labeled as being “physical” climate models. But typical climate GCMs would all be “physical” climate models since their whole setup is formulated to model explicitly the hydrodynamic and thermodynamic processes of climate. One such model is the GISS ModelE for which the FORTRAN code is available from the GISS webpage at http://www.giss.nasa.gov/tools/modelE/
While we speak of the greenhouse effect primarily in radiative transfer terms, the key component is the temperature profile that has to be defined in order to perform the radiative transfer calculations. So, it is the Manabe-Moller concept that is being used. In 1-D model calculations, such as those by Manabe-Moller, the temperature profile is prescribed with the imposition of a “critical” lapse rate that represents convective energy transport in the troposphere when the radiative lapse rate becomes too steep to be stable. In 3-D climate GCMs no such assumption is made. The temperature profile is determined directly as the result of numerically solving the atmospheric hydrodynamic and thermodynamic behavior. Radiative transfer calculations are then performed for each (instantaneous) temperature profile at each grid box.
It is these radiative transfer calculations that give the 33 K (or 150 W/m2) measure of the terrestrial greenhouse effect. If radiative equilibrium was calculated without the convective/advective temperature profile input (radiative energy transport only), the radiative only greenhouse effect would be about 66 K (for the same atmospheric composition), instead of the current climate value of 33 K.
I wonder if you have a response to the comment I made above regarding ModelE? -> Richard, December 1, 2010 at 10:27 am
Thanks
Dr Lacis
Thanks for your reply. I was wondering about the Fultz and Rossby kind of stuff
At last
A site where different perpectives can be sensibly discussed without rancour, insult or deletion. Judith, if this keeps up we might send you to sort out the middle east…..
David –
“Why don’t the planetary surface conditions matter?” Yes, some do, of course. For instance, I should have said “…the outward LW radiation [must] be equal to …that portion of the the impinging SW radiation not reflected by the surface as outward SW radiation.”
But Miskolczi thinks that it is important to eliminate the discontinuity in temperature at the surface that the Milne formalism imposes, and this cannot be done without introducing physical mechanisms beyond those described by the purely radiative equations (and attendant approximations). Specifically, the Eddington approximation divides the radiation field into upward and downward fluxes (each semi-hemispherically isotropic). The Milne equations describe the spatial variation of these fluxes as a function of optical depth, given their values at a single altitude. The only place where the values are known a priori is at TOA. (It may help to think of these fluxes as ‘wave-like’: you can launch a wave at a point where you specify its properties, but how those properties change as it propagates through space are determined by the medium, in this case the optical depth as a function of altitude.) So one cannot simultaneously impose conditions at two altitudes on the downward LW flux, independent of the properties of the intervening medium. This characteristic is manifested mathematically by the fact that the governing differential equations are second order, requiring two boundary conditions, one (and only one) for each component of the flux.
A consequence is that there is a discontinuity between the temperature at the base of the atmosphere and the solid surface, the surface being warmer because it receives both the downward SW radiation and the downward LW radiation from the atmosphere (the so-called ‘back radiation’). The magnitude of the discontinuity diminishes as total optical depth increases (the surface and air become more strongly coupled, as one might expect), but radiation alone does not erase the discontinuity. Miskolczi has a problem with this, but Nature does not, as convection, evaporation and other modes of heat transfer are adequate to the task of handling the discontinuity. As we know, in the terrestrial atmosphere the usual situation is that convection extends far up in the troposphere, so the formal discontinuity issue does not even arise. A convective profile (e.g., moist adiabat) is matched to a rigorously calculated radiative profile, as you indicate. Why Miskolczi tried to base an energy minimization scheme on the purely radiative equations all the way to the surface is a mystery to me.
I hope this helps.
Pat Cassen
Thanks Pat for the clarification of your previous comments.
Miskolczi is beginning with a 1D radiation problem to quantitatively model a planetary “greenhouse”, and working out from that. By finding what radiation can or cannot do, that exposes what must be done by convection, precipitation, clouds etc.
I understand your point of 2 fluxes, 2 boundary conditions.
You note: “So one cannot simultaneously impose conditions at two altitudes on the downward LW flux, independent of the properties of the intervening medium. ”
“The only place where the values are known a priori is at TOA”
However, with a gas above a solid planet, the radiative properties of the surface affect the surface absorption & radiation of both SW and LW and the surface temperature. This gives more parameters necessitating more boundary conditions. Those will affect the surface temperature and consequently upward SW reflection as well as LW radiation. I don’t see how you can model a planetary atmosphere with a solid surface without that. (With a totally gaseous planet this is not required.)
The portion of SW absorption & reflection requires a SW absorptivity parameter. Miskolczi assumes a black body.
The portion of LW absorption & reflection requires a LW absorptivity parameter.
Miskolczi again assumes a black body.
Internal planetary heat radiation approximated to zero for the initial model.
(A future refinement would be use average planetary absorptivity and emissitivity.)
Miskolczi starts with the actual data on the atmospheric profile for 11 geographic regions. He fits this to obtain the empirical atmospheric profiles.
See Zagoni Slide 68 where he shows the actual global average temperature lapse rate profile) from the radiosonde data. Then he shows his fit to that with his “semi-transparent” model. That fit appears to be good. Note that it is more accurate than the USST-76. Note particularly the major difference in water column between the USST-76 and actual global average based on the available data.
Contrast Milne’s “semi-infinite” model which seriously diverges from the global average – being warmer at higher altitudes and cooler near the surface. Note the very large surface discontinuity in the Milne model.
You note: “but radiation alone does not erase the discontinuity. Miskolczi has a problem with this, but Nature does not, as convection, evaporation and other modes of heat transfer are adequate to the task of handling the discontinuity.”
Setting the surface boundary temperature equal to the atmospheric temperature, appears to be equivalent to setting no fluid boundary resistance, equivalent to high convection.
The resulting error compared to the global average temperature profile appears to be small. See Zagoni Slide 68. I agree that this should be relaxed in future modeling to provide a more accurate local surface temperature and absorptivity emissivity.
From that he conducts a detailed calculation for all radiatively active species (“greenhouse gases”), for 150 layers, in 9 different directions. He applies a solar (Planck) weighting, to then find the global Plank weighted optical depth. I believe this assumes constant solar radiation, zero LW input, and a blackbody lower surface.
He does this both for the actual TIGR data and for the NOAA reconstruction. See Zagoni Slides 69 and 79.
From that he calculates the optical depth from annual data for the last 61 years, including all variations in water, CO2 and temperature with depth. See Zagoni Slides 58-60.
Note the very small variations in total global optical depth over the last 61 years.
You note: “Why Miskolczi tried to base an energy minimization scheme on the purely radiative equations all the way to the surface is a mystery to me.”
Separate out Miskolczi’s global optical depth evaluation vs subsequent theoretical modeling. With multiple atmospheric components, the gas proportions can change. e.g. CO2 increasing. More importantly, H2O can increase or decrease depending on temperature. i.e. precipitation and ice formation. The equilibrium properties of water provide another constraint. Then the gravitational field & pressure lapse rate come into play. The atmospheric height or lapse rate also changes with temperature and Miskolczi accounts for this change.
For a future full thermodynamic development see Essenhigh:
Prediction of the Standard Atmosphere Profiles of Temperature, Pressure, and Density with Height for the Lower Atmosphere by Solution of the (S−S) Integral Equations of Transfer and Evaluation of the Potential for Profile Perturbation by Combustion Emissions Robert H. Essenhigh Energy Fuels, 2006, 20 (3), 1057-1067 • DOI: 10.1021/ef050276y
So may I encourage you to review Miskolczi’s optical depth evaluations vs his theoretical modeling in more depth.
David –
Thanks for your response, which I just now found.
You state: “…the radiative properties of the surface affect the surface absorption & radiation of both SW and LW and the surface temperature. This gives more parameters necessitating more boundary conditions.”
More parameters, but not more boundary conditions. (Mathematically speaking, adding parameters at the surface does not change the order of the differential equations.)
You can demonstrate by direct calculation that Miskolczi’s ‘solution’ violates the boundary condition at TOA; it requires a non-zero downward LW flux from space, which is unphysical. His ‘solution’ is invalid; it is not a correction to Milne. I emphasize that you can, with pencil and paper, show this for yourself.
“Setting the surface boundary temperature equal to the atmospheric temperature, appears to be equivalent to setting no fluid boundary resistance, equivalent to high convection.”
Yes, but high convection then negates the validity of Milne’s (and Miskolczi’s) purely radiative equations. His prediction of a preferred optical depth depends on a minimization of radiative transport all the way to the surface, where, in fact, transport is dominated by convection at the surface. So, even if he had done the math right (he hasn’t), the analysis is irrelevant.
You (and tallbloke, I guess) are impressed by the fact that Miskolczi derives an average atmospheric optical depth from a theory (which is demonstrably flawed in concept, methodology and mathematical derivation), which matches that derived (to three significant figures!) from a deficient data set. I am only suspicious.
I urge you to take seriously the other critiques of Miskolczi that I previously linked. (Here is a link to the Dorland and Forster critique.)
Thanks for the discussion. I offer you the last word on this.
Pat, thanks for the link, I will read and try to learn. I am not an expert in radiative physics, my training is in using others knowledge to help me assess theories and the operational processes which build data validity, an art in itself, not an exact science.
I do wonder how badly flawed the radiosonde dataset is though. I have a couple of reasons for thinking it might not be as bad as has been made out. And I can see some motivations for doubt being cast on its validity which might not be directly driven by fully objective criteria.
David – In the above, I should have said “…negates the applicability…”, not “…negates the validity….”
From my comment:
“A higher surface temperature will cause a higher convective flux and a higher radiative upwards flux. (Increase in energy from the surface)..”
Nullius said on December 2, 2010 at 12:10 pm:
“I’m not entirely sure, but by emphasising the word “from”, I suspect that you’re still making the assumption that convection can only transport heat upwards, never downwards. Convection (in the sense of a bulk air movement induced by temperature differences) can transport heat both ways. “Convection” refers to the entire cycle../i>”
I’m not making the assumption that convection can NOT transport heat downwards.
Generally the surface is at a higher temperature than the atmosphere and so convective heat flux is upward.
However, I don’t think I gave a good explanation before – at least, it was much too brief. Let me try again.
In the case where “greenhouse” gases increase:
1. the radiative cooling to space is at higher altitude
2. therefore, from a colder temperature
3. therefore, less radiative cooling.
(As noted before and no disagreement between us).
What happens now?
Less cooling to space means that the climate system progressively stores more heat (until a new steady state is reached).
This is how the climate system warms in a general sense.
But how does the surface temperature change specifically?
a) If the atmosphere first increases in temperature then the atmosphere will radiate more to the surface. = More back-radiation which will increase the temperature of the surface.
b) If the surface first increases in temperature then convective and radiative flux will then increase the temperature of the atmosphere above. = More back-radiation which will increase the temperature of the surface.
There is another effect – the more opaque the atmosphere the lower the effective radiative altitude of the downward radiation. (If the atmosphere was transparent it would not radiate at all).
Nullius said:
“..So long as the temperature profile of the atmosphere is adiabatic, and hence linear, the temperature at any point is related to the temperature at any other point as a simple function of the gradient of the line and the difference in heights and nothing else. Unless the back radiation can affect one or the other of these, it cannot possibly have any effect..”
It’s a confused statement.
The surface temperature is determined specifically by the balance of fluxes at the surface.
It’s quite simple and should be uncontroversial. If back radiation was unimportant then if it dropped the surface temperature would be unaffected.
At 15’C, a 1’C increase in temperature – for a surface like the ocean – increases the radiative flux by 6 W/m^2.
Yet with a 1’C increase in temperature – if the back radiation has not increased and the solar radiation has not increased and the convective flux has not changed – then the surface will cool. Because an extra 6 W/m^2 is being lost.
Very simple and surely no one disagrees with this fact?
So the only way an extra 6W/m^2 can be radiated is if an extra 6W/m^2 is received at the surface.
This is what I mean by the fact that “back radiation” is a complementary effect.
Saying back radiation “has no effect” seems like such a strange statement I think I haven’t understood the point of the statement maker..
Scienceofdoom,
Please keep in mind that heat transfer is not due to the level of energy exchange, but only due to the net difference of energy exchange. If you keep increasing back radiation due to a hotter lower atmosphere, but at the same time increase forward radiation due to a hotter ground (both on the average), any heat transfer would only depend on the difference, and which transfer direction was larger. On the average the upward radiation is slightly higher than back radiation, so all net radiation heat transfer is up. The main heat transfer over the average Earth is convection driven up to the altitude where radiation out occurs. Since there is no net heat transfer down (on the average) from back radiation, there is no heating from back radiation, and back radiation is a result of, not cause of atmospheric greenhouse effect. It is not complementary, it is an effect. Back radiation has no effect means it does no heating.
“Saying back radiation “has no effect” seems like such a strange statement I think I haven’t understood the point of the statement maker..”
I think that’s quite possible. It’s also possible that I’ve made a mistake and am missing something. So I’d like to pursue this a little longer.
I’ll pick up my pan of water analogy again. A pan of water is boiling on the stove – what is the explanation for its temperature being 100 C? If we turn up the gas, what happens to the temperature?
On the one hand, it is true to say that the temperature is determined specifically by the balance of heat fluxes in and out of the water. There is the heat conducted in through the base from the gas, the heat output from radiation from the sides of the pan, from the water’s surface, and via evaporation as steam escapes. We can say that the temperature is 100 C because of the precise balance of conduction, radiation, and evaporation. Clearly, the gas being on “has an effect” – and if we turn the gas up from 2 to 4, the detailed heat fluxes will change. Similarly, if we replace the matt black pan with a shiny silver one, the radiation out from the sides of the pan will change considerably, again changing the heat fluxes.
So if you want to say that the temperature of the water is determined by the heat fluxes in an out of it, then the reason that the water is at 100 C requires that you include gas setting and the pan colour. They are a part of the specific reason for the temperature.
What I am trying to say is that they don’t actually matter, because the convection/evaporation term will always increase or decrease in such a way as to maintain the temperature at exactly 100 C. The temperature is controlled by convection/evaporation, which ‘dominates’ the other effects in a dynamic sense (as opposed to in magnitude).
Likewise, with the atmosphere. The convection will always increase or decrease to maintain the adiabatic lapse rate, and the surface temperature is simply the effective radiative temperature (-20 C) plus the lapse rate (6 C/km) times the difference in altitude of the average emission altitude and the surface (about 5-6 km).
To get any other value, you have to change one of the inputs (e.g. by claiming that back radiation changes the adiabatic lapse rate), or falsify one of the basic assumptions (e.g. by saying that convection is impossible and the thermal profile of the static atmosphere is stratified). I’m open to the possibility, but I can’t figure out which one you’re saying is wrong.
I get the impression that you’re trying to say that without back radiation, convection would be impossible. Like saying that if you turn the gas off, the water would stop boiling. But that would be to misunderstand the point I intended to make.
Your discussion contains four basic values: temperatures at the earth surface and at the tropopause, the altitude of the tropopause and the lapse rate. One equation connects these three values. The lapse rate is determined by the properties of the atmospheric gas. We have still two independent values that must be determined from additional conditions.
One of these remaining conditions is related to the factors that determine where the convection stops. The last one is determined by the energy balance, i.e. by the condition that there is no net flow of energy to the troposphere. The amounts of CO2, H2O and other greenhouse gases affect this energy balance through changes in the radiative energy transfer within the troposphere. These radiative energy transfers include back radiation.
I wonder whether disagreements about back radiation are more about semantics than physics. Individual IR photons back radiated to the surface will impart kinetic energy to the molecules of water or terrestrial components, thereby warming them. On a global average, however, the net flux is from surface to atmosphere, and so one can describe the net effect as a reduction in cooling rather than as a warming.
Also, averaged globally, convection is quantitatively more important than radiation in moving sensible and latent heat upward to where it will be radiated to space. However, this varies with latitude. In the warm tropical oceans, convection strongly dominates, whereas at cooler latitudes with less atmospheric water, radiation plays a larger role. Radiation is also a necessary background for convection. Increased latent heat rising from the surface requires surface warming (or reduced cooling) via down-dwelling radiation. In addition, the air overlying ocean surfaces is generally saturated with water and can’t sustain increased evaporation unless it is warmed, which occurs mainly via greenhouse gas radiative transfer.
As far as I know, current theory and models base their conclusions on a combined radiative/convective equilibrium paradigm.
See Ferenc Miskolczi’s quantitative Line By Line (LBL) long wave (LW) radiation modeling
(vs summaries/interpretations.)
I’m not sure whether these are all purely semantic differences, but it sounds to me like NiV says that backradiation does not matter, only the lapse rate matters. As Nick Stokes writes here – an N2 only atmosphere will still have the dry adiabatic lapse rate, but the surface will be at 255K and emit 235 W/square meter and the atmosphere will progressively cool as you go higher into the atmosphere based on the dry adiabatic lapse rate. Effective radiation height is the surface of earth. Backradiation will however change the surface flux and hence the surface temperature. Using the lapse rate, you can determine where the effective radiation height lies. In the case of the N2-only atmosphere, it lies at the surface of the earth and when you add greenhouse gases, it lies somewhere higher.
In other words, we still need a blackbody emitting at 255K for energy balance with the sun, however, the earth’s surface will be at a higher temperature because of the backradiation. Using the lapse rate, you can determine at what height energy balance was achieved with the sun.
“In other words, we still need a blackbody emitting at 255K for energy balance with the sun, however, the earth’s surface will be at a higher temperature because of the backradiation.”
It will be at a higher temperature because air descending from the emitting black body altitude to the surface will be compressed.
Convection is not the process that creates the actual temperature difference. Its role is to prevent the difference from being twice as large. You need the back radiation to reach the actual lapse rate in the atmosphere.
Would you agree that convection is the process that controls the magnitude of the temperature difference?
I agree that convection is an essential controlling factor in the tempertature difference. The power that feeds the effect has also an important role. The more back radiation, the more heating power and the higher temperature difference after conduction has done its part.
Conduction keeps the result essentially linear in power.
Conduction? What part is played by conduction?
Error. I meant convection.
OK, good.
Given the length of this thread, I don’t think anything is to be gained by dragging the debate out endlessly here. I’m sure the subject will arise again, here and elsewhere.
The essential point I had hoped to make was that convection was the mechanism that controlled the magnitude of the warming. And I certainly agree that back radiation constitutes a large part of the surface heat flux in practice. We’ll leave the hypothetical thought experiments for another time.
I add only, that I have been learning a lot during the last couple of days. I have a strong background in physics, but on many details of atmosphere I had only rather vague knowledge. Reading these threads including your messages has helped me in getting things sorted.
Now I join many others in thinking, how one could include all essential features in a description, which is essentially correct in all respects, but still sinple enough to present in a relatively brief space. I do not know, whether it is possible, but I have some ideas.
RB – I admit I sometimes have difficulty interpreting what is intended in certain comments. In any case, back radiation is an essential element of the greenhouse effect. The surface radiates upward towards space. Without greenhouse gases, that radiation would escape unimpeded, and the Earth’s temperature would be much colder. In the absence of back radiation, the same thing would happen even in the presence of greenhouse gases – these would simply be acting as “relay stations” for IR photons headed upwards. My point about semantics was simply that if back radiation makes the surface warmer than it would be otherwise (which it does), the disinction between “warming” and “reduced cooling” is a disagreement more about descriptive terminology than about what is happening to the temperature.
Fred,
There is some semantics involved. I think L. Weinstein is saying you cannot say “backradiation warms” because net heat transfer is only in one direction. If that is the terminology, I agree. I however think NiV is wrong and scienceofdoom is correct. My position is that:
1. For energy balance, we need ablackbody radiating at 255K.
2. Backradiation results in a higher flux and higher resulting surface temperature than 255K
2. The physics behind a constant lapse rate determines that the black body at 255K is obtained at a greater height as you increase the amount of GHGs. That is, to conform with the physics behind the constant lapse rate, as you add more GHGs, the atmospheric layer has to become thicker.
Stated differently, if you have x-y=k (a constant), as you increase y (the backradiation), the value x (surface radiation) has to increase.
Can you expand on point 2, please? Why does a higher flux result in a higher surface temperature? Why does it not result in more vigorous convection, and the same surface temperature?
Nullius,
Assuming that earth is surrounded by a series of concentric shells, the shell closest to earth is radiating in both directions and the last absorber and re-radiator is the earth’s surface. Therefore, the surface cannot stay at the same temperature as without the GHGs.
If you have a fixed electrical current that you have to force through a resistor, as you increase the resistance, the potential gradient that develops across the resistor has to increase. Back-radiation essentially is a resistance to the flow of heat from earth to space. As the back-radiation increases, you need to establish a greater temperature difference between the surface and the effective radiation height to force the heat flux through the atmosphere.
“the potential difference that develops across the resistor …”
The shell model would result in an exponential temperature profile and an average surface temperature of 45 C. This is contradicted by observation.
The surface does not get that hot because it is “short-circuited” by convection, that kicks in as soon as the gradient exceeds a set value. So long as the surface stays below the threshold, convection slows to a stop and you are left with the radiative/conductive resistance, but the moment it goes over, the “circuit-breaker trips” and convection drops the resistance to upward heat flow dramatically, cooling the surface.
(For those who know some electronics, a reverse-biased Zener diode does something like this.)
Or to take another example, if you boil water on gas setting 2, it’s temperature is 100 C. If you turn the gas up to 4, a greater heat flux is entering the water, but it’s temperature remains at 100 C. How is this possible?
My question is, why does a higher flux result in a higher temperature? I don’t see how one logically follows from the other.
Nullius,
The shell model is to illustrate that surface temperatures have to be higher than without the GHGs because a blackbody absorber is also a blackbody emitter and the shell radiates in the IR regime in both directions and that every IR emitter (and absorber) is in equilibrium with the IR emitters surrounding it. Back-radiation is therefore a boundary condition to be applied in solving for the vertical temperature profile. Convection places a constraint on the temperature gradients permissible to less than models that used radiative equilibrium alone and has to be used in conjunction with radiation models to explain tropospheric temperatures. Convection-imposed lapse rate is therefore a limiter that will also have to be satisfied. Therefore, convection has to be used in conjunction with the backradiatio