It is difficult these days to get a paper published in a mainstream climate journal if it emphasises the uncertainty associated with some basic aspect of global warming.
But occasionally it happens, and the research establishment then tends to get its knickers in a knot. Its actions can range from simply ignoring the paper’s existence to vengeful attempts at removal of the relevant journal editor. Of course the professional (and ethical) re-action should be to publish a rebuttal pointing out all the scientific problems with the original paper. This is fine in principle, except that the dice of the publication stakes are still loaded in favour of the politically correct, and the rebuttal can be fairly loose. The problem is that the tone and substance of the rebuttal is more-or-less immaterial in the grand scheme of things. The important thing is to have the last word in the formal literature. With the passage of time, loyalty to the establishment ensures that “Jones has raised doubts about Smith’s result on the grounds of……” becomes “Jones has shown Smith to be an idiot and his results are nonsense”. Its all a bit 1984-ish.
The fuss about Andy Dessler’s response to Roy Spencer and William Braswell’s paper on cloud feedback has a certain déjà vu to it. It seems to me (as a biased observer) that Dr Dessler is becoming more than a little industrious in his use of rebuttal papers to defend the concept of long-term positive feedback in the climate system.
A couple of years ago, three of us produced a paper pointing out that, if one were prepared to believe the NCEP re-analysis trend of middle-tropospheric humidity, one would also have to believe that the long-term feedback of atmospheric water-vapour is negative. Some time later, Dessler and Davis submitted a short paper to JGR effectively saying that nobody in his right mind would believe any such trend coming out of NCEP data. And of course they may have a point. However, I was one of the JGR reviewers of their paper, and for various reasons was not too happy or complimentary about it. In the end it was published without any real attention to the objections. Fair enough, editors have to make decisions like that.
Eventually however I got around to submitting to JGR a formal comment on Dessler and Davis’s paper. It was effectively a tidied-up version of the review comments. In due course it was knocked back by JGR on the grounds (mainly) that it had no new research to report. Which is a bit strange since it was only a comment, not a research paper.
Anyway, the comment ran as follows. It seemed reasonable at the time.
Comment on “Trends in tropospheric humidity from reanalysis systems” by Dessler and Davis
Dessler and Davis (2010) are of the opinion that the negative trends of specific humidity in the middle and upper troposphere which appear in the National Centers for Environmental Prediction (NCEP) re-analysis data are spurious – and therefore that overall water vapour feedback in the climate system is indeed positive and is an amplifier of global warming. The trends were reported and discussed by Paltridge, Arking and Pook (2009), hereafter referred to as P09. Dessler and Davis support their opinion with:
(a) Comparison of the NCEP trends with the trends in four other re-analysis data sets. The comparison indicates that the three more recent re-analyses all have positive trends in the middle and upper troposphere.
(b) Correlations in each of the re-analyses, including NCEP, between specific humidity q at various levels and surface temperature T. They all show that, at least for short-term change on time scales less than 10 years, the correlations are positive and thereby indicate positive feedback.
(c) Comment that the concept of long-term positive water-vapour feedback is in accord with virtually all the independent lines of evidence: models, observations, theory, and newer re-analyses.
RE (a): The NCEP re-analysis relies on balloon observations of water vapour, whereas all the other re-analyses use satellite data of one form or another. Some of the other re-analyses use balloon data as well as satellite data. The ECMWF ERA40 re-analysis includes balloon data, and has a tendency toward negative trends of mid-level (roughly 400 and 500 hPa) specific humidity. The Modern Era Retrospective-Analysis for Research and Applications makes use of balloon data, and if one excludes the obviously anomalous El Nino year of 1998, the tropical mid-level q of that re-analysis has no significant trend one way or the other.
Raw balloon data (e.g. tropical radiosonde data as discussed briefly in P09 for instance) seem to show a negative long-term trend of q at mid-levels. Raw satellite data (as mentioned in P09 and by Dessler and Davis for instance) seem to show a positive trend.
So the most likely and straightforward explanation of the difference between the outputs of the re-analysis schemes is that they (the schemes) are actually behaving as they were intended – namely, they are simply reflecting the behaviour of their different sources of input data. If so, then the issue is not whether some re-analyses are newer than others, but which source of input data (balloon or satellite) has the greater potential for error, and whether, in either case, those errors would or could lead to the trends that are observed. Any significant attempt to resolve such a question would have to consider not only the potential errors of both the balloon and the satellite information, but also the possibility that different sorts of satellite data have been introduced into the re-analysis schemes at different times over the 30-year period since 1979.
The point here is that it is distorting the situation somewhat to give the impression that the NCEP re-analysis is a single “outlier” pitched against a number of other independent re-analyses and can therefore probably be discarded. If one ignores the question as to which are the more reliable as input data (i.e. satellite or balloon data), the balance of ‘likelihood of verisimilitude’ between the NCEP re-analysis and the others has to be more like 50:50.
And therefore it is also distorting the situation somewhat to discuss the well- known problems associated with balloon measurements and make no reference to the many and various problems associated with satellite data. It is difficult enough to believe trends of total water vapour content of the atmosphere from past satellite measurements, let alone the trends of water vapour concentration at any particular level.
Re (b): Much of the Dessler and Davis discussion is devoted to the possibility flagged in PO9 that the long-term correlation between middle and upper level specific humidity q and surface temperature T might be negative even though the short-term correlation is positive.
Dessler and Davis say that there is no theory to explain such a difference in the sign of the correlations. Suffice it to say that P09 contains considerable discussion concerning two (admittedly only qualitative) theoretical suggestions as to how such an eventuality might occur. The suggestions concern possible causes of long-term increase in the stability of the lower atmosphere – an event which, according to the NCEP data, indeed seems to have occurred over the last few decades, and which, if real and continued, could confine a long-term increase of water vapour concentration to the convective boundary layer. One of the possible causes is the relatively large increase in radiative heating in the middle troposphere associated with increasing CO2. This is not to say that such theories are correct, but the absence of any reference to them by Dessler and Davis suggests a reluctance even to contemplate arguments on the other side of the fence.
Dessler and Davis make the point that there is poorer agreement among the re-analyses about the q vs T correlation on time scales longer than 10 years than there is about the correlation on time scales less than 10 years. They attribute this to “handling data inhomogeneities” having more impact on long-term trends than short-term trends. This is of course possible. But they could also have pointed out that, at least at face value, the slopes of the long-term correlations displayed in their diagram are generally a lot less than those of the short-term correlations, and that some of them are indeed negative at certain levels. The thing to remember here is that even a reduction of slope (if it were verified) would be very significant in the overall water-vapour feedback story.
Re (c): Superficially the statement is impressive. One wonders however what is this theory that is supposed to be an independent line of evidence – apart, that is, from the individual bits of theory so far built into the models. And in view of the discussion above about whether reference to the “newer re-analyses” is really germane to the issue, one wonders also about the significance of those analyses in the present context. And in view of the fact that the veracity of models relies (among many other things) upon the observations on which they are based, it is pushing things a bit far to say that models are truly “independent” evidence. Perhaps more to the point in the context of models, their long-term trends of q depend, among other things, on a correct simulation of vertical sub-grid-scale diffusion – the contribution of which is one of the most difficult characteristics of models to verify independently.
The bottom line here is that “virtually all the independent lines of evidence” probably boil down only to the observations. And at the moment, bearing in mind the discussion with regard to (a) above, there is still a lot of work to be done to establish just what the observations are telling us. The issue of the magnitude and sign of long-term water vapour feedback is far from resolved.
REFERENCES
Dessler, A. E., and S. M. Davis (2010), Trends in tropospheric humidity from reanalysis systems, J. Geophys. Res., 115, D19127, doi:10.1029/2010JDO14192.
Paltridge, G. W., A. Arking, and M. Pook (2009), Trends in middle- and upper-level tropospheric humidity from NCEP reanalysis data, Theor. Appl. Climatol., 98, 351-359, doi:10.1007/s00704-009-0117-x.
Biosketch: Garth Paltridge was a Chief Research Scientist with the CSIRO Division of Atmospheric Research before his appointments as Director of the Institute of Antarctic and Southern Ocean Studies at the University of Tasmania and as CEO of the Antarctic Cooperative Research Centre. He retired in 2002, and is currently an Emeritus Professor with the University of Tasmania and a Visiting Fellow at the Australian National University.
Moderation note: this is a technical thread and comments will be moderated for relevance.
The fact that no trend has been observed in SH or RH is quite intriguing, and quite an obstacle for someone who would want to blame the decrease in Cloud Cover as a positive feedback to rising temperatures. If decreasing cloud cover was a product of temperature, (and not the other way around) you would expect the water cycle to speed up, and produce more water vapour. But this just has not been seen, which indicates to me that the Cloud Cover has been driving the temperatures, and there is so much evidence to suggest that Clouds are a negative feedback, and that they have contributed to about all of the warming in the late 20th Century- the part where CAGW scientists claim that natural cycles could no longer explain the warming that occured there.
Would suggest souring the grapes a little less in the introduction.
The wounded sense of persecution colors one’s reading.
The language from the very beginning is loaded: there is the weather and there is climate but there is no such thing as climate change.
The grapes aren’t sweet; they’re sour. They weren’t ripe.
==============
I think it’s understandable for Professor Paltridge to wish to defend his earlier conclusions, particularly if he believes he has been prevented from doing this in the peer-reviewed literature. It adds to the stature of this blog that he is given a forum here. I also agree with his final comment that water vapor feedback is not a completely resolved issue, if that means that all uncertainties are removed. It appears that even the speed of light as an absolute limit, heretofore considered completely resolved, is being challenged by CERN results consistent with a superluminal speed for some neutrinos. We have to be careful before considering any conclusion final.
On the more mundane issue as to whether we can have high confidence in at least the positive sign of water vapor feedback, despite lesser certainty about magnitude, I would recommend that readers review Professor Paltridge’s comments in light of the paper by Dessler and Davis that he has graciously linked to. Particular attention should be paid to the upper troposphere, which more than the mid-troposphere, determines flux imbalances at the tropopause that would link increased water vapor to reduced OLR. From Dessler and Davis, it appears that all of the reanalyses, including the NCEP one, show a positive slope when specific humidity is regressed against surface temperature, indicating positive feedback – at least for the short term correlations (see Figure 2) – and that only the NCEP data deviate from this pattern long term, with the others continuing to show a positive slope. Dessler and Davis also cite other evidence that suggest that the NCEP data include spurious values (e.g., in association with El Nino warming). That paper also references another informative 2005 study by Soden et al in Science that uses an indirect method for estimating the warming/humidity correlation, and arrives at similar conclusions for a positive feedback.
Ultimately, it’s hard to quarrel with Professor Paltridge’s assertion that the conclusions depend on the quality of the data, and readers will have to judge this in the context of all the reanalyses. It is not out of the question that the NCEP data may be better than all the other reanalyses plus Soden et al, despite questions raised by Dessler and Davis, and this possibility can’t be settled here. However, I will add one more element to the story as to a possible reason for problems with the NCEP negative humidity trend. It’s speculative, and I don’t have all the data at hand, but it’s interesting as a possible mechanism.
The declining humidity trend with time in the NCEP data is not a smooth curve, but more a series of downward jumps. Each apparently followed an improvement in the humidity sensors that shortened their response time. As a result, later data at any given altitude were less and less contaminated with residual humidity measurements from a different altitude. This would explain a negative humidity trend in the data that is not an accurate reflection of actual humidity values. There are many pitfalls with all sources of measurement, radiosonde as well as satellite, and so it’s hard to attribute putative errors to any specific mechanism. Nevertheless, the reanalysis data newer than the NCEP dta appear to have rectified some of the inaccuracies associated with earlier measurements, and there is some reason for confidence that their conclusions are probably more trustworthy.
For additional discussion of some of the above, the Science of Doom two-part series is informative.
I find the CERN results amusing in light of the conversation I’ve been having off and on with Steven Mosher about what is know-able. I can remember working at HP in the 80’s and being told by a PhD product engineering manager that it was physically impossible to build an LCD panel bigger than 13″ due to defect densities – and believe me, he ‘knew.’ I still think scientists blind themselves to the miraculous with knowledge, and that they should begin every sentence with “what we currently believe is.” And does anyone wonder if the onion will just keep unpeeling forever in physics? That there will always be one more particle or effect no matter how far you go?
It’s turtles all the way down.
I have one more thought. I enjoy watching the Ghost Hunter style shows on TV. I am interested in how they take instruments into environments and see what they do. How many scientists, I wonder, will just turn on an instrument in some random environment just to see what it does. I recall an episode of Fact or Faked where the invesitgators went to Argentina and took some kind of signal analyzer out to the coast to see if they could pick up on UFOs. When they got there, there was a very powerful signal present they did not expect (as it turns out the earth has a signal you can pick up with the right instrument – news to me). There was a huge number of sea lions on the beach at the time. As the people watched the instrument another very strong signal showed up and at the same time the sea lions stampeded up the beach in a frenzy. Nothing appeared that was out of the ordinary. In a little while, though, a huge electrical storm appeared on the horizon. My curiosity in this regard was piqued not by the instrument picking this up, but by the sea lion behavior. How were they picking up on the thing? This is much like my question. How often is the anomalous discarded when it should be questioned? I can remember endless times in engineering classes being told that this or that ‘goes to zero,’ ‘is neglible,’ or ‘can be ignored,’ never mind the infamous ‘QED.’ Is there any wonder left in science or are scientists trapped by their hypothesis and their expectations?
Fred Moolton wrote: Particular attention should be paid to the upper troposphere, which more than the mid-troposphere, determines flux imbalances at the tropopause that would link increased water vapor to reduced OLR.
Sidling sideways to a policy question, if the upper troposhphere increases in temperature in response to CO2, and the surface does not (which is possible because the sunshine warms the surface first, CO2 in the air column absorbs OLR, and the atmosphere is never in equilibrium), should we care?
Doesn’t your comment open the idea that the layers of the troposphere, probably loosely defined “layers” without real barriers between them, respond differentially to changes?
MattStat – You raise the complex issue of Lapse Rate, which is the change of temperature with altitude as determined by the hydrostatic relationship.. Because under stable conditions it is adiabatic (no heat added or subtracted for an air parcel moved from one altitude to another), It is isentropic and tends to reestablish itself when perturbed by warming aloft, as long as there is enough convective mixing to permit that to happen. Without water vapor, the dry adiabatic lapse rate is about 9.8 C/km – i.e.,temperature declines by that amount with each increase in altitude. This is true for our planet’s gravity, and would differ elsewhere. Whether it would also apply in an atmosphere with no greenhouse gases has been debated but is irrelevant to our climate. The dry adiabatic lapse rate can be described by two properties of the atmosphere, in that it is the value of gravitational acceleration divided by the specific heat capacity of air at constant pressure. This emphasizes that it is determined by the physics of the atmosphere as a gas independent of unrelated climate variables.
Water vapor reduces the lapse rate, because as it rises to colder altitude, it condenses to release latent heat and thereby warm those altitudes. The saturated adiabatic rate is about 5 C/km. In most regions, the measured rates are somewhere in between although often closer to the saturated adiabat.
When CO2 or another greenhouse gas reduces outgoing infrared radiation at the tropopause to create a warming effect, that temperature increase is paralleled at lower levels according to the lapse rate as long as the warming at those lower levels through the greenhouse effect does not exceed the adiabatic lapse rate. On the other hand, the ghg effect, which operates throughout the atmosphere, typically raises low altitude temperature above the adiabatically determined lapse rate temperature. This creates an instability because the warm air tends to rise by convection until it restores the adiabatic lapse rate. Thus, the latter tends to put a ceiling on the reduction in temperature with altitude. The physics of the greenhouse effect would not tend to do the opposite – increase temperatures more at high altitudes than lower altitudes.
To summarize some of the above, the physics of gravity and the gas laws determines how temperature changes with altitude. Greenhouse effects will either leave this unaltered in the long run (e.g., a temperature increase at one altitude will be mirrored at others), or will cause a temporary increase in the lapse rate that is restored by convection.
Finally, there are regional and temporal variations from the above, depending on what the climate is doing. In addition, the stratosphere has a “negative lapse rate” (temperature rises with altitude) due to the presence of ozone which warms upper layers by absorbing solar UV.
Fred re:
“Greenhouse effects will either leave this unaltered in the long run (e.g., a temperature increase at one altitude will be mirrored at others), or will cause a temporary increase in the lapse rate that is restored by convection.”
Following are some thoughts on some items I have seen:
Lapse rate varies with GHG absorptivity
Yes that is the first order physics. More rigorously, it appears that the lapse rate also incorporates the absorptive/radiative properties of the greenhouse gases. See: Robert H. Essenhigh,
Energy & Fuels 2006, 20, 1057-1067
“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”
This was followed up by Sreekanth Kolan
Study of energy balance between lower and upper atmosphere
These quantitative 1D thermodynamic models may provide an objective means to evaluate differences in measured concentrations of H2O and CO2 versus the reported lapse rates between the balloon and satellite data.
Refine kp using LBL Code
The kp parameter incorporating greenhouse gas absorption coefficients could be refined by quantitative Line By Line (LBL) models. e.g. See: F.M. Miskolczi et al.: High-resolution atmospheric radiance-transmittance code (HARTCODE). In: Meteorology and Environmental Sciences Proc. of the Course on Physical Climatology and Meteorology for Environmental Application. World Scientific Publishing Co. Inc., Singapore, 1990.
Mass of the Atmosphere
scienceofdoom below refers to: K.E. Trenberth & L. Smith
The Mass of the Atmosphere: A Constraint on Global Analyses, J. Climate, Vol. 18, 864-875
K. Trenberth et al. Accuracy of Atmospheric Energy Budgets from Analyses
This could be used to refine the Essenhigh/Kolan models.
Look forward to your comments & other papers etc.
David – I could access only Essenhigh’s abstract, not the full text. I’ve only skimmed the Trenberth and Smith paper, but I have a fairly good sense of its main points.,
I think Essenhigh’s paper is consistent with the principle I described earlier that water vapor as a component of the greenhouse gases in the atmosphere will tend to move the lapse rate away from the dry adiabat and in the direction of the saturated adiabat, which is a lower rate. Because CO2 should not have this effect, the relative proportions of CO2 and water will be reflected in the lapse rate.
The paper by Trenberth and Smith uses surface pressure, an index of atmospheric mass, as a tool for evaluating water vapor, and finds significant flaws in the reanalyses it evaluates, most particularly in the NCEP data. Although this throws doubt on the validity of the latter, I would have to say that it is less informative in telling us about atmospheric water vapor where it counts most – the upper troposphere. Most atmospheric water is in the lower troposphere, where its effect on OLR is relatively small. Conversely, the concentration in the upper troposphere is critical in determining greenhouse effects, yet the total amount there is so much smaller than the quantity at low altitudes that measurements of total precipitable water tell us little about what is happening at the critical high altitudes. For that process, I believe the reanalyses and other evidence in Dessler and Davis, as well as additional evidence cited by Science of Doom, is useful in demonstrating the high probability of an increase in upper tropospheric humidity with increasing temperature, consistent with a positive water vapor feedback.
I didn’t read the Miskolczi reference, but it’s my understanding that his work contributed significantly to our knowledge of radiative transmittance measurements. I believe that will be a more important element of his scientific legacy than his more recent efforts.
Fred
There is an interesting paper by Gilbert arguing for a different thermodynamic model of the lapse rate:
William C. Gilbert, The Thermodynamic Relationship between Surface Temperature and Water Vapor Concentration in the Troposphere, Energy & Environment · Vol. 21, No. 4, 2010 pp 263-276
Appreciate you comments on Gilbert’s methodology.
Specific humidity increasing with temperature does not necessitate strong positive water vapor feedback. We could have increased clouds and/or increased precipitation resulting in mild positive or even negative feedback. e.g. see George A. Ban-Weiss, Govindasamy Bala, Long Cao, Julia Pongratz, Ken Caldeira, Climate forcing and response to idealized changes in surface latent heat and sensible heat and the Water vapor feedback: evaporation
(There is also the separate issue of solar modulation of galactic cosmic rays forming clouds.)
“Specific humidity increasing with temperature does not necessitate strong positive water vapor feedback.”
Conceivably, the correlation could be non-causal, in which case it wouldn’t tell us about feedback, but if the humidity change is due to the temperature change, I think it would have to be considered a positive water vapor feedback, with a temperature amplifying effect due to the infrared-absorbing properties of water vapor. It seems to me the data are convincing in regard to this particular feedback.
Clouds form from water vapor. However, cloud feedback is not water vapor feedback, is less well understood, and might differ in magnitude and conceivably even in sign. The Ban-Weiss et al paper suggests that a negative contribution to cloud feedback would occur if sensible heat loss were replaced by evaporative heat loss, but it doesn’t indicate whether net cloud feedback is positive or negative.
It’s noteworthy that the major feedbacks that modify temperature responses to CO2 or other atmospheric constituents – water vapor, snow-ice albedo, lapse rate, and clouds – all involve the presence of water. Without water, planetary feedbacks would be much diminished.
Some of this was discussed in the water vapor feedback thread, and my perspective there is relevant to this discussion, so I won’t repeat it here.
David L. Hagen wrote: These quantitative 1D thermodynamic models may provide an objective means to evaluate differences in measured concentrations of H2O and CO2 versus the reported lapse rates between the balloon and satellite data.
My question to you is the same as my question to Fred: how much inaccuracy is entailed in a 1D thermodynamic model, when we are studying sunrise-induced warming, cloud formation, and afternoon rainfalls and other cooling?
As a first-order approximation, treating the atmosphere as well-mixed and looking at equilibrium relationships may be good enough (say, good enough for explaining differences among Venus, Earth and Mars;, but for looking for the effects of a CO2 increase on near-surface temperatures over 5 decades or so it could be so inaccurate as to be useless.
cf this quote from Trenberth, that you quoted: The diagnostics reveal major problems in the NCEP reanalyses in the stratosphere that are inherent in the model formulation, making them unsuitable for quantitative use for energetics in anything other than model coordinates.
MattStat
I agree that the 1D is an averaged rate. Diurnal dynamic effects will modulate that. e.g., see Willis Eschenbach’s diurnal temperature and cloud explorations.
Fred Moolton, you wrote: Water vapor reduces the lapse rate, because as it rises to colder altitude, it condenses to release latent heat and thereby warm those altitudes. The saturated adiabatic rate is about 5 C/km. In most regions, the measured rates are somewhere in between although often closer to the saturated adiabat.
As you can see by watching cloud formation in real time, this is not spatially homogeneous. It is also a transient, as the sun warms things from sunrise to early pm, and then things start to cool with rain here and there (or else overnight fogs and dews.) How much of what you describe of “the physics” is an equilibrium approximation to a spatially homogeneous mixture?
Good questions. The dry adiabatic lapse rate is pure physics, but deviations from it are a function of climate variables, including the effects of geography, season, and altitude, among other variables. Here, a combination of models and observational data are used to advance our understanding. In the case of clouds, models use parametrizations as an attempt to simulate within grid cells what the average behavior of clouds would be if they could be accurately reproduced at every specific location and time within the grid, which is something currently beyond the reach of models. In other cases, we have both good observational data and an understanding of basic principles for a reasonably accurate perspective. For example, it’s known that under certain circumstances where the ground can cool rapidly from radiative heat loss, a temperature inversion can occur, with ground and surface air temperature lower than that at slightly higher altitudes (the reverse of the ordinary lapse rate). This can be temporarily stabilized via the physical principle that cold air tends to remain under warmer air, and so some new perturbation in ground temperature or air turbulence may be required to dissipate the inversion. There are of course many other examples of deviation from the adiabat, and for an accurate understanding of how they are incorporated into models, you would need a professional climate modeler, or at least someone more familiar that I am with model development for an accounting.
It’s interesting, though, that despite these caveats, standard lapse rates are not a bad way to anticipate the effects at the surface of radiative imbalances created at the tropopause from an increase in greenhouse gases. An example is the temperature change anticipated from a doubling of CO2 if no feedbacks operated – so-called “no feedback climate sensitivity”. This can be estimated by differentiating the Stefan-Boltzmann equation in conjunction with good estimates of the forcing (at about 3.7 W/m^2). The calculation yields a temperature change of almost exactly 1 deg C, based simply on translation of a temperature change at the higher altitudes down to the surface via a linear lapse rate. GCMs model the same thing, utilizing variations in latitude, seasonality, etc., to account for the heterogeneities. Their estimates for the “no feedback sensitivity” average about 1.2 C, which is higher but not dramatically different from the simple version based on Stefan-Boltzmann and assumed linear lapse rates. I cite this example to illustrate the principle that modeling all the variations you mention doesn’t necessarily lead to dramatic changes in our expectations. However, we can’t test empirically whether the models have correctly estimated climate responses in the absence of feedbacks, because feedbacks do occur, and so observed responses always include their effects.
Fred Moolton wrote: However, we can’t test empirically whether the models have correctly estimated climate responses in the absence of feedbacks, because feedbacks do occur, and so observed responses always include their effects.
I think that the data available now do not rule out the possibility that increased CO2 will lead to increased am temperature rise and increased mid afternoon cloud cover and decreased late pm temperature. I could be wrong, but I also expect this to be researched energetically in the upcoming years.
Thanks for your responses.
Whether it [the dry adiabatic lapse rate] would also apply in an atmosphere with no greenhouse gases has been debated but is irrelevant to our climate
Irrelevant? Why? It is important to fully understand the link between the DALR and the greenhouse effect. If there is still a debate then there must be some uncertainty and scientists generally shouldn’t like uncertainty. Although Judith may not agree with this sentiment!
If it can be established that one the former cannot exist without the latter then we do effectively have almost conclusive proof that the GHE is real.
Fred is referring to an argumentation with me. We agree on what he wrote above “as long as there is enough convective mixing to permit that to happen”, i.e. we agree that the adiabatic lapse rate is obtained, when there’s enough convection. What we were arguing about was, whether there would be convective mixing in total absence of GHG’s. My view is that there would not be, while Fred wasn’t so sure (I think he considered the question open having some preference on the opposing view). On the other hand I’m also ready to accept that the required GH effect may be very much weaker than the present one on Earth. My claim was directly applicable to exactly zero emission and absorption of LW IR and I didn’t present any specific upper limit for the validity of my claim.
Such questions may be tests on the understanding of physical processes, but the answers to such hypothetical counterfactual questions have indeed no direct relevance on, what happens in the Earth atmosphere or any other planetary atmosphere that has been studied.
Nothing in the disagreement between Fred and me was related to the radiative processes, but on the extent of convection in such hypothetical atmosphere. My view is that it would be limited to a very thin layer, while some others doubt that view. My view is that such an atmosphere would not have any real troposphere, but the tropopause would touch the surface and stratosphere start at a very low altitude.
This is meant to be a comment to Matt’s latest above w/r/t morning heating and afternoon cooling, though I’d appreciate any responses. I have one comment and one question.
Comment: Briefly, I think enhanced GHG effect is supposed to increase nighttime temperatures faster than daytime. I’d have to reacquaint myself with the reasoning behind this but I think some evidence has been found to suggest this is occurring. Additionally, I wonder over how much of the globe would it matter, if the effect you are highlighting occurs. Nonetheless if it hasn’t been thoroughly researched, I would think it merits effort as you say. Also, here is a link to an older paper I found which seems to address the question, from GRL, 1994.
http://www.agu.org/pubs/crossref/1994/94GL00188.shtml
The question is this: It has been highlighted on perhaps this blog or at Climate Audit, that “raw data” often comes at us in the form of daily or monthly means, and that diurnal variation and possibly day-to-day variation is lost. Going back to let’s say hourly temperature profiles, this represents several additional orders of magnitude in the data processing requirements. How do you come up with statistical to strike a balance between more accuracy and data overload in this sense? Does it make sense to separate the day into say 4- or 6-hour chunks, and do spatial averaging on these values?
Pekka – convection seems to be a ubiquitous to fluids that are heated from below. What wouldn’t an atmosphere of nitrogen, for example, exhibit convection over land heated by the Sun? If you believe it wouldn’t, what do you think would stop it?
For Bill C.: thanks for the link. Follow David L. Hagen’s link to the work of Willis Eschenbach.
For David L. Hagen, I agree with you that something good will come from Willis Eschenbach’s efforts. I have downloaded some of the TOA/Pacific data, and I hope to do something informative with them.
Jim2,
The convection would be stopped by the warming of the atmosphere. It would be so warm that even the warmest areas could not induce convection that would extend far from the surface.
The warming is due to the lack of any effective cooling mechanism that would prevent it from warming to the temperature required by the above. The only cooling mechanism would be through convection and conduction to the colder areas of Earth surface, but there would be a very strong temperature inversion in those areas that would make that cooling very inefficient.
Pekka – so your point is that because a gas like nitrogen doesn’t radiate in the infrared, it can’t cool the atmosphere by radiation into space at TOA. Since it can’t cool, the body of the atmophere, along with the surface of the Earth, would continue to heat up and the limit to the heating would be when the surface radiation comes into equilibrium with the incoming solar radiation. Since the atomosphere would be fairly uniformly hot, it wouldn’t support convection?
Right. The only energy transfer into and out of the atmosphere would be with surface. The heating is relatively efficient through convection as long as the surface is even locally warmer than the atmosphere, while cooling is always inefficient. This would lead rapidly to the situation, where the potential temperature of almost all atmosphere is close to the hottest areas of the surface. Even on the warm side the energy flux is limited by the fact that the first step through the skin layer of the atmosphere would be largely by conduction as convection doesn’t extent effectively to the first skin layers. (In the Earth atmosphere radiative energy transfer is much more efficient than conduction.)
When that is first true for the potential temperature, the convection ceases and the really weak conduction is strong enough to bring the atmosphere gradually towards isothermally warm, i.e. towards a warm stratosphere that extends almost to the surface.
There would still be some cooling by the colder areas of surface, but a temperature inversion is certain to be created and that would become very steep as the only heat transfer through that inversion would be by conduction and turbulent mixing created by the remaining circulation. This circulation would be maintained by the temperature differences of the surface areas, but it would be limited to a low altitude by the temperature profile of the atmosphere. It would also be weak, because all circulation is dependent also of the cooling energy transfer, which is weak in presence of the inversion.
As the atmosphere would be weakly coupled to the surface, the surface temperature would always be close to what it would be without any atmosphere. It would vary strongly between different areas and also between night and day.
I am thinking the night-side would cool fairly rapidly. This might give rise to a “terminator wind.”
Thinking a bit more, I see your point about the low level of mixing, even due to the night side. While the surface might cool rapidly from OLR, the atmosphere still has no ready means of cooling. Cooling of it would happen near the surface. But still, the average global temperature would be brought down by the cool, night-side surface. This is an interesting thought experiment. Have you or anyone you know of calculated the global temp of an Earth with no water and a nitrogen atmosphere?
http://retractionwatch.wordpress.com/
http://blogs.nature.com/boboh/2011/01/11/banned-no-not-me
http://branemrys.blogspot.com/2011/04/synthese-problem.html
http://scienceofblogging.com/post-publication-peer-review-blogs-vs-letters-to-the-editor/
http://blogs.nature.com/from_the_lab_bench/2011/09/22/public-engagement-with-science-what-it-means
http://www.guardian.co.uk/science/peer-review-scientific-publishing
http://www.guardian.co.uk/commentisfree/2011/sep/23/bad-science-ben-goldacre
From http://www.guardian.co.uk/commentisfree/2011/sep/23/bad-science-ben-goldacre (above)
The dangers of cherry-picking evidence
It’s one thing to produce a bias-free experiment – but the second, crucial stage is to synthesise the evidence fairly
The biggest problem in Paltridge, Arking & Pook (2009) was that they made no comment on the very significant paper The Mass of the Atmosphere: A Constraint on Global Analyses by Trenberth & Smith (2005).
This shows that NCEP/NCAR has more problems in water vapor trends than ERA-40 (and of course that both reanalyses have problems).
An extract from Trenberth & Smith for interest to summarize the idea:
“The total mass of the atmosphere is in fact a fundamental quantity for all atmospheric sciences. It varies in time because of changing constituents, the most notable of which is water vapor. The total mass is directly related to surface pressure while water vapor mixing ratio is measured independently.
Accordingly, there are two sources of information on the mean annual cycle of the total mass and the associated water vapor mass. One is from measurements of surface pressure over the globe; the other is from the measurements of water vapor in the atmosphere..”
There are other issues in Paltridge et al (2009) in that the detailed analyses of water vapor trends directly from radiosondes generally find positive IWV.
An extract from Water Vapor Trends – Part Two:
“This is why we have reviewed Ross & Elliott (2001) and Durre et al (2009). These papers review the actual radiosonde data and find increasing trends in IWV. They also describe in a lot of detail what kind of process they had to go through to produce a decent dataset. The authors of both papers also both explained that they could only produce a meaningful trend for the northern hemisphere. There is not enough quality data for the southern hemisphere to even attempt to produce a trend.
And Durre et al note that when they use the complete dataset the trend is half that calculated with problematic data removed.
Perhaps Trenberth & Smith (2005) and Ross & Elliott (2001) are flawed in some way. It’s just that Paltridge, Arking & Pook (2009) didn’t comment on them.
The ice core proxies of global average temperature data of the last 10,000 years of earth’s climate show that the climate system has been very stable. Anytime it warms up by a deg C or 2 (most of the time within 1 deg C), it then gets colder within a deg C or 2 of the long term global average, and vice versa. Any attempts to predict global average temperature in the future require that the natural mechanisms that have resulted in the extremely stable earth’s climate since the last major Ice Age be well explained and understood.
As water vapor is by far the most important and abundant greenhouse gas in our atmosphere, and if greenhouse gases have an important role in controlling global average temperatures, then it would seem that the most likely answer is that net feedbacks from water vapor in the atmosphere have a stabilizing influence on global averge temperature. If I wanted the outcome of my research to have the best chance of being correct, I think I would be focused on explaining why water vapor changes in the atmosphere have a stabilizing influence on global average temperatures. Any weak theories to the contrary wouldn’t get past my “manager level” sanity check, and I would send the student (or employee) back to the drawing board to make a stronger case for their weak theory, or more likely find a more fruitful avenue of research….and I would probably recommend against trying to publish weak theories that they will be embarassed by later when the truth is finally known with great confidence.
I recommend serious researchers of this issue study the work of Ewing and Donn from the 1950’s and 60’s (1. Science, 15 June 1956, Vol. 123, N0. 3207; 2. Meteorological Monographs, Feb. 1968, Vol. 8, No. 30 American Meteorological Society) to understand the very strong feedbacks of polar region ice and snow albedo cycles, and how these cycles are related to (1) ocean currents, (2) an Arctic ocean that has lost most of its sea ice in warm periods such as we are experiencing now, (2) an Arctic ocean that is covered with sea in colder and lower humidity parts of the cycle (3) the atmospheric humidity cycles related to global temperature changes and Arctic ocean sea ice coverage, in search of a cyclic atmospheric humidity mechanism that can explain the amazing long term stability of the earth’s global average temperature.
Easy research money from a politically biased government and special interest groups, that desire to convince a gullible public that human related releases of hydrocarbons into the atmosphere are the cause of recent global warming trends, have taken many climate change research scientists’ “eye off the ball” when it comes to proving the root cause of the most recent global warming trends. These warming trends, which seem to have mysteriously maxed out about 12 years ago, are well within the global average temperature excursions of the last 10,000-12,000 years that were not caused by human related releases of CO2 into the atmosphere.
Because of its tendency to condense, water vapor is a slave to the temperature of the atmosphere, while CO2 can control it more by varying independently of any prior temperature (e.g. through emission by volcanoes or other sources). So in paleoclimate, it is CO2 changes and its emission mechanisms that have mattered. A good paper is by Lacis, Schmidt, Rind and Ruedy (2010) in Science (the CO2 control knob paper).
Note also that the lapse rate depends on the moisture and vice versa. See Essenhigh and Kolan.
That’s Robbert 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” Energy & Fuels 2006, 20, 1057-1067
The sour grapes were the point of the post and what followed was proof. I think he proved his point and shared some science along the way.
Moisture & Standard Atmosphere vs TIGR
Essenhigh and Kolan assume the US Standard Atmosphere in their models of the atmospheric lapse rate. However, Miskolczi averaged the TIGR data to recalculate the lapse rate and found substantial differences between the data and the 1976 standard atmosphere. He particularly found the precipitable water to differ by a factor of 2:
2.61 prcm in TIGR versus 1.26 prcm in USST-76.
See: Poster presentation at the European Geosciences Union General Assembly, Vienna, 7 April 2011 Slide 3/28
S. Vey et al. 2010: Validation of Precipitable Water Vapor within the NCEP/DOE Reanalysis Using Global GPS Observations from One Decade. J. Climate, 23, 1675–1695. doi: 10.1175/2009JCLI2787.1
Trenberth, Kevin E., John T. Fasullo, Jessica Mackaro, 2011: Atmospheric Moisture Transports from Ocean to Land and Global Energy Flows in Reanalyses. J. Climate, 24, 4907–4924.
doi: 10.1175/2011JCLI4171.1
This suggests there are still substantial uncertainties in reanalysis data, and especially in precipitable water in light of TIGR data, as well as a need to reevaluate the “standard atmosphere.
Robert Essenhigh Energy & Fuels 2006, 20, 1057-1067
The Essenhigh paper is of questionable relevance, because it’s dependent on the the following (direct quote from the paper):
It’s, however, well known that the use of a single absorption coefficient is not satisfactory. Many things can be calculated correctly even using this approach, while many others will be misrepresented very seriously. Thus it’s not possible to know without major additional analysis, what results to trust a what not to the least. The agreement with empirical data or more accurate models for some phenomena is no guarantee at all that something else would be correct.
To me such a model is of no value for finding, what’s true. It may have educational value, when applied with care, but it can also be seriously misleading from an educational point of view due to the problems that I discussed above.
One obviously erroneous conclusion that is made in the Essenhigh paper concerns the importance of CO2 as GHG, because this is one of the points that the single absorption coefficient cannot represent correctly at all.
I looked also at the master’s thesis of Kolan. The Figure 16 is quite interesting as it tells semiquantitatively, how each component of the radiative flux depends on altitude. I use the word “semiquantitatively”, because the approximations made mean that the figure doesn’t describe accurately the real atmosphere.
Use of the single absorption coefficient is one of the problematic assumptions, but perhaps even more problematic is the use of a profile for the whole globe. A model of global average cannot describe well in detail the average of various parts of the world, because many things are not linear in such a way that the average would satisfy the same physical equations that are valid separately at each location.
Someone has looked at the trends in weather balloon humidity measurements.
http://www.metoffice.gov.uk/hadobs/hadth/
http://www.metoffice.gov.uk/hadobs/hadth/McCarthy_2009.pdf
Judith Curry
Thanks for bringing this (PO9). It is something that has been on my mind for some time.
I have always thought that the NCEP re-analysis data on decreasing specific humidity trend since 1948 were strange, in view of IPCC model estimates and general theory of increasing specific humidity with warming (to almost result in constant relative humidity in lock-step with Clausius-Clapeyron).
When I plotted the NCEP data on specific humidity against the HadCRUT3 temperature record I noticed that the long-term trend was indeed one of negative water vapor feedback, but that shorter-term “blips” in the record seemed to show the opposite trend, just as PO9 have observed:
http://farm4.static.flickr.com/3343/3606945645_3450dc4e6f_b.jpg
The short-term “blips” would also correlate with the findings of Minschwaner + Dessler 2004, which found short-term increase in specific humidity with warming, however not enough to even come close to resulting in constant relative humidity, as assumed by the IPCC models.
M+D Fig.7 (IPCC assumed water vapor increase versus actual observed)
http://farm4.static.flickr.com/3347/3610454667_9ac0b7773f_b.jpg
My first reaction (not being a climate scientist) was that maybe there is a long-term “natural thermostat” function that acts to regulate our climate (possibly through increased low-altitude cloudiness or precipitation), to offset the fact that short-term warming can cause short-term increase in atmospheric water vapor leading to increased GH warming.
When I showed the above graph at RealClimate, I got the standard response from Gavin Schmidt, namely that the NCEP data are incorrect. When I asked him why they are still being published, he simply deleted my question. End of discussion.
I’m glad to see that this topic is now being revisited, rather than simply swept under the rug.
The Dessler and Davis reaction that
is obviously an “argument from ignorance”.
IMO until someone comes up with some pretty solid long-term data invalidating the NCEP record, the PO9 conclusion holds:
Max
“When I asked him why they are still being published, he simply deleted my question. End of discussion.
“I’m glad to see that this topic is now being revisited, rather than simply swept under the rug.”
As In understand it, the data are not so much incorrect as imperfect. They might not be useful for long-term studies, but if one is aware of the potential pitfalls, they can still perhaps be used for shorter term and process studies. I don’t think that the NCEP reanalysis was every conceived to provide a perfect long-term climate record.
Max – As described above, the NCEP reanalysis was invalidated by measurements of atmospheric mass showing changes in water vapor inconsistent with the NCEP data. Additionally, all five reanalysis studies (including NCEP) showed a positive slope correlating temperature with mid and upper troposphere humidity in short term studies (i.e., indicative of a positive feedback). All also showed the same thing long term except NCEP. The mechanism for the NCEP dispairty can’t be decided with certainty but is most likely due to instrumentation changes that increased the response rate of humidity sensors, so that later data were less contaminated with humidity values from atmospheric altitudes other than the one being measured. This would show up in long term correlations, but not in short term ones, where NCEP agreed with the other reanalyses.
Satellite studies outside of these reanalyses also showed the positive humidity trends (Soden et al, Science 2005), and differed from Minschwaner and Dessler in finding approximately constant relative humidity – the RH issue is unsetlled.
At this point, I think it is close to a certainty that there is a positive correlation between temperature and specific humidity, with the magnitude of the response remaining to be defined better. The various references cited in many of the above comments (including the SOD article) help to provide further details, and in my view are worth taking the time to go through..
Fred Moolten
Has it occurred to you that 50+ years of actual physical observations may actually invalidate the rebuttal you have cited (which you claim “invalidates” the long-term record)?
A physical observation is worth a thousand computer studies, as you know.
Soden et al. 2005 is interesting both in what it says and in what it does not say. It combines model simulations with an up-dated set of clear-sky radiances from HIRS satellite observations over several years, with the statement:
Adding the footnote:
Soden discounts the much longer NCEP radiosonde record, which shows exactly the opposite trend to the one, which his study has found, with:
My question to Soden would be simply:
Sure there ” is a positive correlation between temperature and specific humidity, with the magnitude of the response remaining to be defined better”, as you write – at least, in the short term, as M+D 2004 showed, and Soden 2005 also seems to confirm..
Contrary to the Soden study, M+D also showed that the observed response was only a fraction of that assumed by the climate models cited by IPCC (i.e. essentially constant RH).
In addition to the magnitude of the short-term response, what is also not known is why the long-term record shows this correlation in short-term “blips”, but also shows the opposite long-term trend. (As pointed out, no one has been able to answer this, as yet, except to simply claim that the data are no good.)
This suggests a “thermostat mechanism”, which tends to balance things out again with a long-term negative feedback. Could the very recent studies on the global impact of evaporation be a possible link, or could there be a local impact from added low altitude clouds or increased precipitation, not picked up by Soden, which again decrease the specific humidity?
The assumption of a climate that increases humidity in lockstep with Clausius-Clapeyron to maintain constant RH sounds good on paper, but is an oversimplification, which does not appear to be validated robustly by actual physical observations.
This issue is not settled, Fred, just because you seem to think it is.
Max.
Max – The answer to all your points, including the evidence invalidating NCEP long term trends, and the evidence that is now compelling for positive water vapor feedback can be found throughout the many comments and references in this thread. You are welcome to ignore it unless you are interested in arriving at an accurate understanding of what water vapor is doing. There remain uncertainties, but the sign of feedback is not one of them.
Fred Moolten
You write:
Sorry, Fred. “Comments in this thread” are no “evidence” of anything.
Nor have I seen any “references in this thread”, which could be considered scientific “evidence” that specific humidity increases with temperature over the longer-term period. “Suggestions”, yes. “Postulations” – yes. “Evidence” – sorry, Fred – no sale.
“Evidence” requires empirical data from physical observations or reproducible experimentation., and the longest data set shows just the opposite.
As the lead article points out:
But, hey, Fred, if you want to believe it is resolved, that’s your right.
Max
Max – What’s unfortunate about this is that water vapor is an interesting subject that deserves detailed attention in view of a number of unresolved issues. To divert the conversation from those issues seems to me to forfeit an opportunity for us all to reach a better understanding of the subject. What I “believe” will be irrelevant to astute readers who read the Paltridge post, and then the Dessler/Davis paper, the Science of Doom series, the Trenberth/Smith paper, the Minschaner paper, the Soden paper (all linked to or referenced in this thread), as well as the comments on those papers and articles and any other source material they wish. If you don’t think the readers will conclude that the evidence for a positive water vapor feedback is a near certainty, and that uncertainties relate to the magnitude, I would say you are probably deceiving yourself. It’s your prerogative, but I believe you could contribute more to these discussions if you focused on elements of the water vapor climate response where there is an opportunity to explore the unresolved elements, and learn something in the process. I also think that when you make untenable claims, you’re showing some disrespect for the ability of other readers to judge evidence.
If some new data or evidence follows this, I’ll continue the discussion. If not, I’ll leave judgment in the hands of readers who wish to review all the material – there’s a lot of it, and it’s quite informative.
Is this another case of confused terminology? Water vapor increases as temperature increases, that is a feedback to warming whether caused by CO2 or not. Water vapor increase, all else held constant, is a positive radiative feedback. Water phase change in the atmosphere tends to be cool, a negative feed back (this is the one I find most interesting).
Dallas – I think what you describe is absolutely correct, but I don’t see any confusion in terminology. As you point out, water vapor provides a positive radiative feedback – the water vapor feedback – but condensation to form water droplets or ice particles creates a negative (cooling) feedback. The term for the latter is the “lapse-rate feedback”.
I mentioned elsewhere (to David Hagen, I think) that almost all feedbacks involve water in one way or another. These include the water vapor feedback, the snow-ice albedo feedback, cloud feedback, and the lapse rate feedback. They also include all biological feedbacks, because life on Earth requires water. Even the carbon cycle feedback (warming from CO2 increasing atmospheric CO2 via redistribution from oceanic and other liquid water reservoirs and the terrestrial biosphere) requires water. There would be little climate feedback without the presence of water.
Even assuming you are correct that feedback is positive, (and I personally think it is somewhat unlikely to actually be negative), isn’t it also important that the feedback really is as strongly positive as the models say. (ie that RH is constant)??
My impression is that most or all of these papers fail to indicate constant RH, especially in the longer term. That would leave us with a WV feedback that is indeed positive, but much weaker than the models say.
Can you comment on that?
Bill – Your point is an important one. Although atmospheric RH can be shown to be fairly constant overall, this figure is dominated by low altitude humidity and is not a clear indication that upper troposphere RH has remained constant. It’s the upper troposphere humidity that most determines the greenhouse effect potency of water vapor.
There is not yet enough good data on upper troposphere RH, particularly for the tropics where the influence would be greatest. Although essentially all of now multiple datasets show specific humidity (essentially the water vapor concentration as a fraction of atmospheric mass) to be rising (the NCEP reanalysis the only exception as discussed elsewhere), the evidence on RH is mixed. Forgive me if I don’t go back and link to the URLs, but the two main sources of observational data can be found as references in the Dessler/Davis paper that Professor Paltridge linked to in his post. Minschwaner and Dessler found a rising specific humidity, but also reported that RH failed to keep pace as a function of temperature. In contrast, Soden et al in their 2005 Science paper reported a maintenance of constant RH, using an ingenious but rather indirect method.
The bottom line is that the water vapor feedback, as you suggest, may be less strongly positive than modeled on the basis of an assumed constant RH. I’m not sure that it would turn out to be “much weaker”, but I can’t exclude the possibility that the difference from a feedback based on constant RH would be significant.
Fred, I do hate these nested comments. Below the atmospheric boundary layer, there is no reason to suspect that RH will not remain constant with rising temperature, on average. Above the ABL, average RH may remain constant on average, I imagine it would be difficult to confirm with all the turbulent air movement. In the upper troposphere, where the radiative impact of water vapor would be most significant, is were most of the uncertainty about water vapor change due to increased surface temperature lays. What I have seen so far, suggests that water vapor at all levels increased as predicted, within the margin of error of the measurements.
I did note that roughly around 1994 that the relative temperature change between the mid-troposphere and the stratosphere began behaving oddly in the RSS data. That data regrouped around 1998 to what would be expected, then started behaving oddly again. This is what I and a few others “believe” is an indication of a thermostatic type behavior.
My description is an atmospheric heat pipe, borrowed from another blog some months ago.
Spencer’s paper(s) appear to be somewhat similar to the heat pipe, but hard to decipher because of his cloud fixation. The best analogy of the heat pipe I can provide is a hail storm weather pattern. Entrained water vapor rises, freezes, falls, melts partially and rises again in several cycles. Each cycle “pumps” heat to the higher level of the atmosphere. This heat pipe effect would tend to increase cloud coverage instead of being increased by cloud coverage. It may be the mechanism that Spencer is looking for, dunno.
The heat pipe effect appears to be enhanced by relatively stable temperatures, causing a gradual decrease in temperature. That makes sense to me because less turbulent vertical air movement would allow more cycles before precipitation. Also, water has a broader radiative spectrum than water vapor which would increase radiative cooling.
That is just what it looks like to me. Max and others may have different thoughts, but I haven’t seen this covered in the literature.
The hea
The ERA-Interim reanalysis has been retroactively run back to 1979 and can be compared to the new NCEP CFSR reanalysis. The former uses 4D-Var while the latter uses the equivalent to GFS’s data assimilation (ditto for MERRA).
The tropical humidity differences in the reanalysis products boil down to a data assimilation problem that is not trivial. However, a simple mean-squared difference mapping between two reanalysis will show that each reanalysis is “anchored” to the radiosondes with the satellite data background errors having the most uncertainty. You should get a map that has the raob stations highlighted –> (ERA-INTERIM minus CFSR)^2
“The thing to remember here is that even a reduction of slope (if it were verified) would be very significant in the overall water-vapour feedback story.”
Dr. Curry,
A conditions required in order for for global warming to occur is that the temperature of mid-troposphere remains unchanged, please see mathematics in my book and Article-12, http://www.global-heat.net. Air temperature above mid-troposphere must decrease and below it must increase. This has been occurring for years and observations are in agreement. Consequently, specific humidity must decrease above mid-troposphere and specific humidity must increase below mid-troposphere. They cancel out for they are equal, and the net change in water vapor content in the atmosphere is negligible. Math and observations are in agreement. Therefore, water vapor feed back story and the consequent cloud feed back story are fiction.
The speed with which Dessler’s rebuttals appear, and the slowness of publication of contrary commentary, has to do, it has been suggested, with the “inclusion” guidelines for AR5. I.e., unrebutted papers published by a rapidly approaching cut-off date must be referenced. Rebutted ones can be ignored.
Guess which bucket your paper and submissions fall into.
Fred and Dallas
Let’s get this straight.
I have not stated that I have concluded that the net water vapor feedback is negative. I agree that this sounds less likely than not, based on the model studies out there.
Minschwaner + Dessler used actual satellite measurements to determine the increase in specific humidity with warming over the tropics.
They found an increase (as you have stated, Fred) but at only a small fraction of the model-based estimates of constant relative humidity.
Soden’s indirect model-derived estimates showed close to a constant RH, but I would have less confidence in these data than in that of M+D, simply because the data used are further removed from actual physical observations.
The NCEP data, for what they are worth (and the odd man out, as you have correctly stated, Fred), are based on long-term physical observations from weather balloons, etc.; they show a long-term decrease in specific humidity but a shorter-term increase in SH with warming.
So, whether we want to admit it or nor, we have a dilemma regarding both the sign and (to an even greater extent) the magnitude of the long-term water vapor feedback.
Dallas, I find your observation interesting
It would be interesting to hear more about how you would visualize this mechanism working in our climate and how the RSS data support the existence of such a mechanism.
Max
I’m so old I remember being mocked at Climate Audit for suggesting that we are ignorant of the sign as well as the magnitude of the water vapor feedback.
========
Max,
When I can describe it better and not score on the crackpot index, I will. I do have a plot that if you look at here, http://ourhydrogeneconomy.blogspot.com/ My graphic skills suck big time, but the orange line is the blue mid-troposphere minus the greenish stratosphere. The subtraction tend to amplify difference and minimize agreement. I was going to invert the strat, but it was a PITA, so be careful drawing any conclusions.
I won’t pursue this too much further, Max, because readers of this thread and the cited source material can judge this on their own. I’m glad you acknowledge a negative water vapor feedback to be “less likely”. I expect most readers will see this as an understatement.
Whether RH is or isn’t maintained remains unsettled, and so it’s not a good idea to draw conclusions about the extent of any deviation.
I don’t think there’s any doubt that the long term NCEP trend is based on a flawed program, for reasons described above – by myself, by SOD in more detail, by Dessler/Davis, and particularly in the Trenberth/Smith paper. Remember that the latter used observational data on atmospheric weight to show an inconsistency with NCEP reanalysis, which is a model-based program. I think the distinction between “observational” and “modeled” can be overdone, but in this case, you can’t claim the NCEP trend to be model independent – in fact, the utility of reanalysis resides in its use of models to reconcile older with newer data..
Fred, you are probably right of course. The RSS data is noisy and they may be having issues with calibration. I still think it is interesting, though. Circa 1994 the stratospheric temperature trend changed to warming while the mid-troposphere maintained its warming trend. That is right at 17 years, so I think I can get away with the term trend.
Stratospheric cooling is complicated, http://www.atmosphere.mpg.de/enid/20c.html so a lot can impact the short 17 year trend, if it is indeed a trend. Comparing the monthly data, I thought the relative changes may be an indication of changes in radiative forcing/feedbacks. There does appear to be changes, just why they appear to start around 1994 instead of 1998 is a mystery.
Dallas – I became interested in stratospheric cooling a couple of years ago because I couldn’t seem to find a decent explanation on the Internet as to why increased CO2 should cause the stratosphere to cool. The explanation given in the site you linked to is wrong. On first glance, it seems plausible, but a little reflection shows why it can’t be correct. Tropospheric IR absorption by CO2 causes every layer of the troposphere to warm, and a warmer atmosphere (with more CO2 to boot) emits more rather than less IR upward. The effect of increased CO2 therefore is to send more IR into the stratosphere in CO2-absorbable wavelengths. (The same reasoning explains why within the troposphere, warming of any individual layer must cause it to emit more rather than less IR into other layers).
The correct explanation is found in Dennis Hartmann’s “Global Physical Climatology”, page 332, and Raypierre’s “Principles of Planetary Climate”, page 215. CO2 has high absorptivity/emissivity in the infrared, but almost none in UV wavelengths. Most stratospheric warming comes from UV absorption by ozone, and so additional CO2 causes very little percentage increase in absorption. On the other hand, at stratospheric temperatures, energy emission is almost entirely in the IR, where CO2 is a powerful emitter. The result is an increase in emissions over absorption until temperature falls to a level permitting emissions to once again balance absorption. Note that this ozone effect is unrelated to the phenomenon whereby loss of ozone causes cooling – that’s a simple matter of the loss of an energy absorber.
Finally, despite all this nice theory, it has been hard to come by observational evidence to test it. Past stratospheric cooling has been due mainly to ozone depletion. With the Montreal Protocol to reduce ozone-destroying CFCs, the ozone layer appears to be on the verge of recovering, but it’s not yet clear to what extent, or how this differs by altitude. Stratospheric temperatures have been fairly flat recently, and without knowing exactly how ozone is changing, we can’t confidently say that the flatness represents the net effect of ozone repletion (to warm) and CO2 increase (to cool). That’s plausible, but not yet confirmed.
Hey, Fred,
I noticed that several sites had inconsistent explanations of strat cooling. That link came from realclimate after their original post in 2004 had been updated a few times. When the guys explaining the effects of global warming get it wrong, it makes ya think. That is the main reason I am skeptical.
For the Atmospheric heat pipe thing, it is a perfect analogy of the role of water in the greenhouse effect as a thermal regulator. A constant relative humidity is a wonderful assumption to simplify computations but about as unrealistic as can be. Two degrees of warming will cause a roughly linear increase in specific humidity at the surface, but that changes the condensation point of the air mass. Unless the lapse rate perfectly increases with increased temperature and humidity, that means lower average cloud height, a negative feed back. That implies strongly, that land use changes that reduce available surface water would have a positive feedback on temperature.
As a HVAC TAB guy, I am well acquainted with poor design and component selection. Regions of instability in a fan performance curve are very similar to a climate with glacial and interglacial operating points. CO2 can shift the system performance curve, but not change the shape of the curve. So without understand water you cannot accurately predict future climate beyond a relatively small range. Ray Pierre’s greenhouse description is prefect for a small range assuming constant relative humidity. Not so good for a system with a region of instability in it performance curve.
A second point, “Tropospheric IR absorption by CO2 causes every layer of the troposphere to warm, and a warmer atmosphere (with more CO2 to boot) emits more rather than less IR upward. The effect of increased CO2 therefore is to send more IR into the stratosphere in CO2-absorbable wavelengths. (The same reasoning explains why within the troposphere, warming of any individual layer must cause it to emit more rather than less IR into other layers).”
Very true. that got me thinking about water in the mid to upper troposphere. The combined spectrum of water allows more radiation to be emitted around the CO2 and O3 spectrum. I tried a while back to get a spread sheet up and running on the change in the rate of emission through the atmospheric window with varying levels of water vapor liquid and solid. with all three phase changes. It crashed.
A few scattered points.
Regarding stratospheric cooling, I argued with Gavin about this on RC one or two years ago. I failed to convince him, but he conceded that Raymond Pierrehumbert is more of a geophysics theoretician than he is (Gavin is mainly a modeler), and so he was somewhat open-minded about it. I found Raypierre’s and Hartmann’s explanations logical, and I haven’t seen any logical alternatives.
On IR spectral shifts induced by CO2, water vapor, and clouds, this is simple in principle but complicated when it comes to quantitation, because multiple absorption coefficients are involved, as well as the effects on absorption of pressure, temperature, and continuum absorption particularly in the “window” regions, which are rendered more opaque at high humidities. A model is needed, complemented by actual IR measurements, to get a good quantitative handle on it. Overall, of course, less IR escapes via CO2 and more elsewhere.
On humidity, condensation, cloud heights, etc. You are certainly right that condensation per se creates a negative feedback by releasing heat at a higher altitude (closer to space) than the altitude at which the heat originated. Cloud effects are a separate phenomenon from latent heat release. Again, this complicated. However, as a general principle, I would suggest there is a difference between circumstances where the ocean warms first (e.g., El Nino) while the atmosphere is still unwarmed, vs circumstances where the atmosphere warms first (CO2 forcing), and the ocean warms secondarily. In the latter circumstance, the immediate atmospheric tendency is toward a lower RH that is then compensated by increased evaporation from the oceans, whereas with El Nino, the immediate effect would tend toward an RH increase compensated by subsequent atmospheric warming. Convection, cloud heights, cloud types, cloud amounts, and regional distributions will differ between the two. This is one of the reasons, I think, why quarrels about “climate sensitivity” based on ENSO data are less relevant than the quarrelers sometimes claim when it comes to long term effects from atmospheric forcings involving CO2, other GHGs, aerosols, etc.
That’s not a strong argument, because convection fills whatever gap is left from other energy transfer mechanisms to stay within limits set by the adiabatic lapse rate. Thus the increased release of latent heat is automatically canceled by a reduction in convection – except that the adiabatic lapse rate is given by the moist adiabat rather than dry.
To get the details right we need more than such simple arguments, as the details are related to the fact that neither the dry adiabatic lapse rate nor the moist lapse rate based on the assumption of continuously occurring immediate condensation in saturated air is really followed. What happens is dependent on the diurnal variations and many other details of the atmosphere at the level of weather rather than climate.
The Figure 2.7 of Pierrehumbert’s book tells, that the dependence of the moist adiabat on temperature is complex, but basically the moist adiabatic lapse rate is going down with increasing temperature in the troposphere. This should lead to negative lapse rate feedback for the surface and to warming of the upper troposphere, but as I wrote above, the assumption of stationary atmosphere that follows the moist adiabat may fail in describing all consequences of real weather effects on a Earth with days and nights. According to that Figure the temperature difference of the moist adiabat between the pressure levels 1 bar and 0.2 bar is about 45 K, when the surface temperature is 320 K and roughly 75 K, when the surface temperature is 300 K, but the lapse rate difference is smaller closer to the surface than in the upper troposphere.
For the surface temperature of 250 K the absolute moisture is so low that it cannot modify significantly the lapse rate from the dry adiabat and the temperature drops from 250 K to 160 K at 0.2 bar. For the surface temperature of 300 K this same effect starts to be important well within the troposphere and the adiabatic lapse rate gets closer to the dry adiabat in upper troposphere, but for the surface temperature of 320 K the moist adiabat is distinctly lower throughout the troposphere.
Pekka, “Thus the increased release of latent heat is automatically canceled by a reduction in convection – except that the adiabatic lapse rate is given by the moist adiabat rather than dry.” What started me thinking about this is the shift in the relationship between mid troposphere and stratospheric temperature between rapid/larger mid tropo changes and slower/smaller changes. Despite the complexities of stratospheric cooling, for short periods this relationship should indicated change in radiative forcing of the strat by the mid-trop (just an indication, quantification would be extremely difficult). For slower mid trop changes there are greater strat changes (this was just in the northern hemisphere, I haven’t compared the southern nor the extents).
An odd shift in this relationship circa 1994 brought this to my attention. Possibly coincidentally, there appears to be a shift in the southern hemisphere rate of temperature increase that appears to be lead by air temperature. Rather dramatic shift actually that is barely noticeable in the northern hemisphere temperatures.
Interesting situation, at least to me.
Pekka – I agree with your statement about complexity, but I would also argue that among other changes, latent heat release is in fact an important negative feedback factor, because it moves the adiabat closer to the moist adiabat, with a lower lapse rate. In the absence of the latent heat release, convection would restore a dry adiabat from a super-adiabatic rate but would not move it to the lower lapse rate of a moist adiabat. It is the latter that ensures that higher altitudes are warmer than even convection would dictate in the absence of latent heat release, thereby allowing radiation to escape to space with less interference.
Fred,
My text “except that the adiabatic lapse rate is given by the moist adiabat rather than dry” did imply more than many might realize. The release of latent heat is the reason for the the difference between dry and moist adiabatic lapse rates. Thus the release of latent heat is essential, but my point is that it’s fully taken into account in the moist adiabat.
Without the complications of diurnal and other weather variability and the delays in the processes of condensation and falling down of the condensed water the moist adiabat would be followed accurately throughout the troposphere above the altitude, where the 100% humidity is first reached, in areas of upwards convection (at low latitudes at the rising side of the Hadley cell). The dry adiabat would apply to areas of downwards convection (at middle latitudes at the falling side of the Hadley cell).
It’s not easy to tell using simple arguments, how much the complications do change the above simple picture.
(Gavin is mainly a modeler) :) Good point.
I do see some interesting things, which have probably been visited before, but water can do neat stuff.
The gospel of the orthodoxy, for example as preached by Dessler (2011), is that CO2 is the driver of climate change. In this view, the climate would remain quite constant as long as the CO2 concentration remains constant. The degree of cloudiness and the global distribution of humidity would remain within narrow confines dictated by the CO2 concentration. If the CO2 concentration were to rise, cloudiness and humidity would change as a response to the increase in CO2 (via a change in global average temperature). Thus, according to this viewpoint, one should be able to plot a measure of cloudiness (or humidity) vs. a measure of global average temperature, and find a direct correlation within limited scatter. However Dessler did not examine how cloudiness varies with CO2 concentration or how cloudiness varies with increased surface temperature due to rising CO2. Instead, he relied on relatively short-term data from volcanic eruptions and El Niño events to examine how cloudiness varied with temperature during these events. He found a very large amount of scatter, which is not surprising. However, he persevered by finding the best straight-line fit to the widely scattered data, and concluded that cloudiness decreased slightly as the temperature rose. It seems more likely that over this short time period, temperature and cloudiness are uncorrelated, and the data are the result of stochastic variations, rather than a cause-effect relationship. Spencer and Braswell (2011) put it very succinctly:
“The sensitivity of the climate system to an imposed radiative imbalance remains the largest source of uncertainty in projections of future anthropogenic climate change. Here we present further evidence that this uncertainty from an observational perspective is largely due to the masking of the radiative feedback signal by internal radiative forcing, probably due to natural cloud variations…. It is concluded that atmospheric feedback diagnosis of the climate system remains an unsolved problem, due primarily to the inability to distinguish between radiative forcing and radiative feedback in satellite radiative budget observations.”
What this means, is that cloudiness and humidity are primarily controlled by large stochastic variations, and there is too much scatter to determine whether changes in cloudiness are directly due to changes in surface temperature vs. innate changes in cloudiness in the internal climate system. It is possible that over hundreds of years with good data, one might discern a trend of variation of clouds and humidity with CO2 variability, but even that is doubtful.
Dessler et al. (GRL, 2008) attempted to derive water feedback sensitivity by comparing data on global temperature and humidity during the winter months of 2006–2007 and 2007– 2008. Dessler et al. (GRL, 2008) also sought a correlation of global temperature with an ENSO index for 2006–2008. Dessler et al. claim that they have found the relationship between surface temperature and water feedback from this paltry data. This seems impossible to this writer. They then reach the rather incredible conclusion:
“The existence of a strong and positive water-vapor feedback means that projected business-as-usual greenhouse gas emissions over the next century are virtually guaranteed to produce warming of several degrees Celsius.”
This conclusion is utterly unsupportable from the analysis of a mere two winters’ data controlled by El Niño activity.
Dessler et al. (JGR, 2008) analyzed a mere one-month’s data in 2005 to infer clear-sky top-of-atmosphere outgoing long-wave radiation (OLR) and its relationship to humidity. It is not clear to this writer that this paper sheds any light on water feedback sensitivity at all.
The work by Soden et al., Santer et al. and Dessler et al. and others shows great ingenuity in ferreting out information from very limited amounts of data, some of which is of uncertain reliability. But ultimately, the credibility of their results is limited by the scarcity of good long-term data. Parameters such as humidity and cloudiness vary widely from day-to-day and year-to-year even in the absence of any forcing. In attempting to determine how these parameters respond to a forcing, one must have data over very long periods to overcome the low signal-to-noise ratios inherent in them. The same problem occurs in sea level measurements. However, whereas climatologists studying sea level have emphasized the need for very long-term data, those who infer feedbacks from humidity and cloudiness seem to be content with very short-term data.
Aside from the science and pseudoscience involved in these analyses, there are social issues as well. The alarmists refer to their interpretation of climate science as simply “climate science”. It is not one interpretation. It is THE CLIMATE SCIENCE – in their view. We see evidence of this in many publications and press releases. In particular, in regard to the effect of clouds, Dessler said: “In recent papers, Lindzen and Choi (2011), and Spencer and Braswell (2011) have argued that … clouds are the cause of, and not a feedback on, changes in surface temperature. If this claim is correct, then significant revisions to climate science may be required. In other words, he regards “climate science” as that which the orthodoxy subscribes to. It is not his interpretation of climate science – IT IS CLIMATE SCIENCE!
Another bizarre aspect of Dessler’s publication was discussed by Pielke, Sr. He said: “Dessler’s paper was received 11 August 2011 and accepted 29 August 2011. This is some type of record … and indicates that the paper was fast-tracked. This is certainly unusual” – to say the least.
“It is not clear whether the Editor of GRL included Roy Spencer as one of the referees, [and if they did not] they were derelict in their responsibilities”. Dessler’s paper should have been submitted to Remote Sensing as a Comment [on Spencer’s paper]. Then Roy Spencer would submit a Reply.”
We are now witnessing a phenomenon in climatology publications that is occurring repeatedly. The climatology orthodoxy has united into an informal association dedicated to (1) prevent contrary analyses and interpretations from being published, and (2) to quickly respond to those few contrarian publications that slip through their net with vitriolic attacks on the paper on orthodoxy blogs, and in the literature via rapid rebuttal publications such as that of Dessler (2011). It is evident that many Editors are in cahoots with the orthodoxy; certainly the Editor of GRL is, and the Editor of Remote Sensing who let Spencer and Bradwell’s paper through the net, suddenly resigned for unclear reasons.
Dessler (2010) and others have estimated the effect of clouds by subtracting the clear sky TOA heat flux from the all sky TOA heat flux but this seems to be over simplistic and always leads to a scatter plot in which the X-Y space is mostly filled with data points – and only a climatologist could believe that a valid trend could be extracted from this mess.
It seems evident from the foregoing discussion that clouds have a major impact on the Earth’s energy balance. According to the analysis of Trenberth, Kevin E., John T. Fasullo and Jeffrey Kiehl (2009) and Kiehl, J. T.; and Kevin E. Trenberth (1997), the global average albedo decreased from 31.3% for 1985-1989 to 29.8% in 2000-2004, suggesting that solar power absorbed in 2000-2004 was 5 W/m2 greater in 2000-2004 than it was in 1985-1989. This is a much greater forcing than that attributed to greenhouse gases. Does this represent a diminution of cloudiness due to global warming (as for example Dessler insists); is it a fluctuation independent of greenhouse gases; or is it just noisy data?
Nice comment, Donald. Thanks for this summary, it was very interesting. Cheers, Rob.
I think I’ve never heard so loud
The quiet message in a cloud.
===============
Donald Rapp
“In this view, the climate would remain quite constant as long as the CO2 concentration remains constant.”
Uh.. What?
Mechanically, for the purposes of calculations and reasoning, ceteris paribus logic might be used, but I have yet to hear a claim from anyone of any doxology that climate is constant.
Perhaps you can offer citation for your claim? As you portray it as a core orthodox lemma, dozens or hundreds of significant climate papers ought have the statement clearly asserted in their introductions.
Until you post such cite as supports your extraordinary claim, I’ll save myself the trouble of wading through the rest of your screed.
It’s in the name Bart. The names are Climate Change, Global Warming… The meaning is CO2GW.
Bart R.: I don’t have time or interest to ferret out the many climate articles that begin with statements such as “The magnitude and impact of future global warming depends on the sensitivity of the climate system to changes in greenhouse gas concentrations” (Gabriele C. Hegerl, Thomas J. Crowley, William T. Hyde and David J. Frame “Constraints on climate sensitivity from temperature reconstructions of the past seven centuries” Nature submission MS2005-07-07962B) or “The Earth’s climate is changing rapidly as a result of anthropogenic carbon emissions, and damaging impacts are expected to increase with warming. To prevent these and limit long-term global surface warming to, for example, 2 °C, a level of stabilization or of peak atmospheric CO2 concentrations needs to be set”. (Reto Knutti and Gabriele C. Hegerl “The equilibrium sensitivity of the Earth’s temperature to radiation changes” Nature Geoscience 1, 735-743.) The only claim that is extraordinary in this matter is your claim that it is extraordinary to claim that it is widely believed that greenhouse gases control the climate and if greenhouse gases were constant, the climate would be constant.
Donald Rapp
Thanks for providing your sources.
The difficulty I have is.. none of them use the word “only” about CO2 causing climate change.
You’ve taken what they all say, and altered it, to construct a Straw Man.
Tch.
So your extraordinary claim fails to meet the standard of proof, and is revealed to be a mere figment of rhetoric.
Anybody want to play with this?
http://ourhydrogeneconomy.blogspot.com/2011/10/so-whats-not-to-like.html
It is pretty much just reinventing the wheel, but I am trying to show why control theory is applicable to climate change using simple ratio and proportioning.
I expect lucia’s worrying it over as we speak. May her edge shatter Damascus steel.
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Dallas
If you’re keen to reinvent the wheel, why not adapt Postma’s Fig. 3 from his otherwise lamentable late addendum to his magnum opus?
Instead of a homogenous Earth, tackle it in 10% bands from zenith of dayside, and slices from sunset to nadir of night. (Or some other patchwork of parts with approximately similar characteristics of temperature and so forth.)
Neglible difference to the overall calculations, I expect, but if you’re going to the level of complexity of using control theory, no reason not to partition, introducing no greater additional complexity (merely more arithmetic and a bit of logic).
Bart, A next step, since the global average is not very descriptive, would be to divide the surface into three regions, northern extent, modified tropics and southern extent. The modified tropics would be defined as the region where half of the incident solar is absorbed.
The three distinct regions would have different heat loss characteristics, with most of the water vapor feed back in the north and little in the south. Kinda the way the Earth is actually responding. I have not read Postma’s latest because I could never get past the weird integration.
Bart R,
Postma’s Figure 3 is better, but the decreasing cooling rate should start earlier and it should have an increasing warming rate on the other side. The hot hat thing is still wrong.
Dallas
Sounds promising.
I look forward to seeing what you produce.