by Andy Lacis
JC note: this essay responds to Garth Paltridge’s recent post Science held hostage in climate debate.
What’s up with Garth?
Why the surprisingly out of touch lack of understanding of what it is that makes the global climate change?
(1) A Very Impressive Radiative Transfer Background
Garth Paltridge and Martin Platt are authors of a rather well-written and well-received book from Developments in Atmospheric Science “Radiative Processes in Meteorology and Climatology” that describes in very readable detail the then existing state-of-the-art in atmospheric radiative transfer modeling in the 1970s. The authors recognize the need for having explicit spectral treatment of both solar radiation and thermal radiation for cloud, aerosol, and gaseous absorbers in the atmosphere. They even take note of the importance of relative humidity effects on hygroscopic aerosols, and of the aerosol radiative impact at thermal wavelengths, long before these radiative effects were included in climate model radiation calculations. All in all, the book is quite relevant for current climate radiation modeling applications – it is only moderately outdated, given the availability of the more rigorous line-by-line and correlated k-distribution calculations that have replaced the less accurate emissivity and Rodgers & Walshaw-type parameterizations.
Given these unquestionably impressive theoretical credentials that demonstrate a very clear understanding of the basic physics of the radiative processes for both solar and thermal radiation in the terrestrial atmosphere, how is it then that these authors have failed to grasp the climatological significance and impact of the steadily increasing atmospheric greenhouse gases, which unchecked, will cause the global surface temperature to increase, and thus seriously disrupt the established climate?
My guess is that they never tried. It is very clear that their principal research interests were in making and interpreting meteorological observations (local by nature), and not in studying the significance of these measurements in their global (climate) context. Also, it appears that the authors may have been lacking a dependable atmospheric modeling capability. This becomes apparent in reading their book – hardly any of the illustrations are of their own making. Most of them are simply taken directly from the published literature to illustrate the physical points that they make in the book. As one example, I find it remarkable that nearly all of the figures from our 1974 Lacis and Hansen paper on solar radiation in the Earth’s atmosphere appear as figures in the Platridge & Platt book to illustrate how best to calculate the radiative heating effects of solar radiation.
While Paltridge and Platt do not explicitly mention the term “greenhouse effect” in their book, or the fact that it is the greenhouse effect that keeps the global surface temperature some 33 K warmer than it would otherwise be, they do take note of Kirchhoff’s law in their introductory chapter and that gaseous absorbers in the atmosphere absorb and emit thermal radiation both upward and downward at their absorbing wavelengths. Nevertheless, they oversimplify the thermal radiation problem much too much by assuming that the net thermal flux at the surface is the window radiation, and that the amount absorbed by the atmosphere is also the same amount radiated downward by the atmosphere. Had they had a capable radiative model of the atmosphere to work with, they would no doubt have come to a better understanding of atmospheric radiation and its role in the greenhouse effect and global climate.
Meanwhile, at about this same point in time, Jim Hansen and a handful of his colleagues at GISS (possessing no greater knowledge of atmospheric radiation than Paltridge and Platt) were developing radiative models of the atmosphere (and a climate GCM) with which to calculate, evaluate, and analyze the radiative impact on the global climate of changes in atmospheric greenhouse gases and other atmospheric constituents. As was amply demonstrated by Hansen et al. (and other climate modelers before), a detailed physical model of the climate system (thermodynamics, hydrodynamics, radiation, etc.) is an absolute necessity to even begin to understand the basic working of the terrestrial climate system, let alone acquire the capability to predict how the climate will change in response to various forcings.
Perhaps Garth thought the climate system too complex to model (by himself), convinced himself that all the climate process uncertainties made climate modeling intractable, and then went astray with his tangential “entropy production” approach as supposedly providing the basis for understanding the nature of global climate change. It should be clear by now that the basic physics of the climate system physical processes can, and are being modeled successfully, that strict conservation of energy, angular momentum, etc. can be maintained, and that very realistic climate simulations can be generated with the current climate GCMs, including determination of the climate system response to large volcanic eruptions and to the continued increase in atmospheric greenhouse gases.
(2) The Perplexing Political Outlook
Then, on the other hand, there is the perplexing material that was posted here earlier by Garth Paltridge. To me, that material appeared totally at odds with the thinking that was evident in Garth’s 1976 book on Radiative Processes in Meteorology and Climatology. Garth should go back and re-read his own book to see if he still remembers the concepts of atmospheric radiation as he once understood them back in the 1970s.
Perhaps there has been a change in his political outlook that explains his thinking. Wanting to believe that the Climategate emails were leaked, instead of having been hacked, then deliberately taken out of context, misrepresented, and misinterpreted, is quite telling. So also is Garth’s select list of the “There are those who . . .” categories.
These political sentiments are then punctuated by the utter nonsense about climate science being some sort of post-normal or post-modern version of what might otherwise be considered “normal” science. This kind of talk is nothing less than some overly-exhausted psycho-babble borrowed from the social sciences where the parties involved have no real clue as what they are really talking about. Physics provides the basic foundation for conducting climate science, and climate science profusely draws and uses information and data from all of the other scientific disciplines.
Simply put, science is about learning how the natural world works. First you use all data available to formulate an understanding of how the world appears to be working, and then you use all data available to verify if your understanding actually works as a full explanation. Then you continue repeating this cycle until it converges.
But Garth has somehow failed to include the end points of his select list spectrum. He left out the one obvious extreme end point – There are those who feel compelled to deliberately distort, misrepresent, and lie about climate science in order to confuse and bamboozle the public on behalf of fossil fuel interests (notably at the Heartland, Cato, and George C Marshall Institutes).
Also, he left out the other end of the spectrum – there are those who conduct research to study the basic physics of global climate science (notably at government supported labs such as NCAR, GFDL, NASA-GISS, and similar institutions in Europe and Asia), bringing together the research results and inputs from many different disciplines (e.g., geology, chemistry, biology, astronomy, archeology, nuclear physics, spectroscopy, engineering, etc.).
It is undoubtedly true that climate science has transformed itself from being a research backwater of a few decades ago into one of the “big” sciences of today. Gone are the days when a lone university professor with paper and pencil, and a slide rule, can sit down and generate some significant advancement in climate science.
As Garth notes, it is therefore not surprising then, that “it is indeed vastly more difficult to publish results in climate research journals if they run against the tide of politically correct opinion” (in reality) a fully demonstrated understanding of current climate science. “Which is why most of the sceptic literature on the subject has been forced onto the web, and particularly onto web-logs devoted to the sceptic view of things.”
Why would anyone want stuff that is patently erroneous, irrelevant, or otherwise deficient to be published in the long-established climate science literature? Clearly, there has to be some sense of quality control to define what we reliably understand in science, and what we don’t. Why not just trash out the junky stuff in the web-blogs where that is already happening? Should anything of value be uncovered, it will surely survive the thrashing, and then it will make it into the peer-reviewed climate science literature and become recognized as a recognized part of current climate knowledge.
(3) “Big” Science vs. “Little” Science
To be sure, the lone professor with the slide rule, whether or not he happens to be a skeptic, or a non-skeptic, is left at a big disadvantage in competing with climate scientists who work at the established climate centers where there are big computers, working climate models, and terabytes of observational data to bring to bear on the pressing questions of global climate change.
That is one of the characteristics of “big” science. Nowadays, it requires team effort to perform cutting edge research in climate science. The lone professor with his slide rule is left to scrounge around the edges of where the principal research action is. He is left to performing statistical analyses on bits of climate data. The results of his analyses will at best achieve limited science information value, and are thus predestined to be of limited interest and have minimum impact as cutting edge material in climate science.
(4) Spectacularly Inaccurate Climate Data ? How So ? ?
Rather surprisingly, Garth complains about the miserable quality of available climate data. “Climate research has to rely on spectacularly inaccurate data from information on Earth’s past climate. Even though there are vast amounts of atmospheric and oceanographic data to play with, together with lots of proxy information from tree rings and ice cores and corals and so on, abstracting a coherent story from it all is something of a statistical nightmare. It gives a whole new meaning to the old saying “lies, damn lies and statistics”.
On the contrary, there is an abundance of excellent climate data. The available ice core data provide a very precise and detailed record of changes in principal atmospheric radiative forcing gases CO2 and CH4, including a detailed record of changes in oxygen isotope ratios from which to deduce changes in global temperature. Likewise, there is available a precise and essentially complete HITRAN data set of line parameters for all atmospheric gases that matter, permitting accurate calculation of the radiative forcings and feedback responses necessary to construct realistic models to study changes in terrestrial climate over all geological time scales.
To be sure, it is not like we have all the climate data that we need or would want. In fact, no amount of climate data will ever be sufficient. All of the climate variables need to be measured more frequently and more accurately than what is presently available. One very specific example is the pressing need to obtain more definitive polarimetric measurements of aerosol radiative properties, a pressing need that is still going unfulfilled.
All in all, observational data and theoretical models are inseparable. Observational data have information content only materializes when there are appropriate theoretical models available that can properly interpret and analyze the measurements. This basic synergism of analyzing ever improving observational data with ever improving theoretical models is what drives climate science to an improved understanding of how the climate system works and how and why global climate is undergoing change.
As a more specific point to Garth: simply by running statistical correlations between the different proxy variables that may have incorporated various aspects of global climate change is not the optimum way to gain understanding of global climate change. The climate system is too complex and too variable to be understood in terms of statistical correlations alone. Detailed physical models of the climate system, and how the climate system changes, are needed to characterize the information content and climate context of the tabulated data that are used climate proxy variables.
(5) That Dreadful Climate Uncertainty Monster
Perhaps the overarching issue that appears to be holding Garth hostage in the climate science debate is that dreadful climate uncertainty monster.
It could be said that a little bit of uncertainty might actually be good in life – it tends to keep people more alert, instills greater interest, and improves their level of attention toward their environment over what they might otherwise have been willing or able to muster.
More importantly, uncertainty does not in any way prevent us from understanding how the climate system works. From this, it follows that uncertainty should not be used as the excuse for political inaction to condone doing nothing to control the ongoing global warming problem that is caused by the burning of fossil fuel by humans.
However, the justification for initiating and taking political action (that may have significant economic consequences) to curtail global warming (note also that not taking political action may have equally significant economic consequences), requires a clear understanding of the nature of the uncertainties (and certainties) that exist in the climate system. And there may be additional uncertainties (as well as surprises) that develop as part of the economic consequences.
There are many different types of uncertainty that are encountered in the modeling of the climate system, and it is important to understand and characterize and quantify them all. One pervasive type of climate uncertainty is what has frequently been referred to as the unforced or “natural variability” of climate. This characteristic type of uncertainty is encountered when running a interactive atmosphere-ocean climate model for thousands of years with no change in the external forcing (other than standard diurnal and seasonal change in solar radiation) exhibits variability (by several tenths of a degree) in the global annual-mean surface temperature, essentially over all time scales.
Why does the unforced global annual-mean surface temperature vary? Basically, the climate system does not respond in small enough energy increments as it is approaching energy balance equilibrium. When clouds form, or precipitation takes place, these local attempts toward achieving energy balance, overshoot the global equilibrium point, leading to new corrective attempts toward energy balance.
Also, there is interplay between the different heat reservoirs with differing heat capacities (or timescales), which spreads the local ‘overshoot’ variability regionally and over longer time scales. This produces a chaotic variability that appears random, but is actually bounded. Running the climate model again, but starting with slightly different initial conditions, will produce a different temporal record, but one which will exhibit the statistical behavior.
Both climate GCMs and the real world exhibit comparable variability. The external forcing is fully controllable in climate models, but its unforced variability is a characteristic of the model physics. In the real world, there are solar cycle variations, episodic volcanic eruptions, greenhouse gas increases, etc., that constitute the external forcings. The climate system responds to these external forcings, and in addition, includes its unforced natural variability in the form of quasi-periodic resonances ranging from months to decades (e.g., JMO, QBO, El Nino, La Nina, PDO), all of which show up in the global surface temperature record.
All of this greatly complicates the analysis for those who seek to find “empirical verification of global climate change” in terms of simple statistical correlations, or linear regressions, between measured changes in greenhouse gas amounts and the observed variations in global surface temperature over some limit time interval. In reality, the global climate is far too complex, the available measurements are much too limited and incomplete, and the time scale that is accessible is way too short for this approach to yield anything other than at best a very limited semi-qualitative understanding of what is actually happening with global climate.
This is where it is important to understand that the natural variability of the climate system represents temperature fluctuations about a zero reference point. Moreover, these random-looking fluctuations most definitely are not random variations (as in random walk), such that given enough time, they could move the global temperature arbitrarily far from its equilibrium reference point. Climate GCMs (and the real world) must conserve energy, so arbitrarily large departures for the equilibrium reference point simply can not happen in the absence of external forcing being applied. Thus, given enough time, the unforced climate will approach its equilibrium point, and averaging over a time scale that is longer than the time scales of the fluctuations will serve to define the point of equilibrium.
(6) The Climate Stuff that is NOT at all that Uncertain
This brings us to the topic of global climate change aspects that are of the more certain and deterministic kind – the stuff that depends on very basic physics that have been well understood for many decades, if not centuries. More specifically, in the climate context, this refers to the radiative forcings that drive global climate change, and include in particular, the anthropogenic greenhouse gases are being accurately measured and monitored, and their radiative parameters that are likewise accurately known and understood.
As in all measurements that have ever been made, there are always going to be some uncertainties. And this applies to the greenhouse gas atmospheric concentrations and their spectral absorption line parameters. But these are very minimal uncertainties that are inconsequential in determination of the contribution that these gases make to the strength of the terrestrial greenhouse effect.
As has been explained in the past, it is the non-condensing greenhouse gases (CO2, CH4, N2O, O3, CFCs, of which CO2 is the principal contributor) that control the strength of the terrestrial greenhouse effect, with water vapor and clouds (being temperature dependent feedback effects) providing radiative magnification.
In short, we need to start getting used to understanding the fact that atmospheric CO2 is the principal control knob (the solar luminosity remaining fixed) that governs the global surface temperature of the Earth. The present atmospheric concentration of CO2 stands at about 400 ppmv. With zero atmospheric CO2, the climate of Earth will plunge to a snowball Earth state (global annual-mean surface temperature of – 30 °C) and kill off most everything that is alive. (Something similar to this happened about 650 million years ago).
With the atmospheric CO2 concentration increasing to about 4% (40,000 ppmv), the global annual-mean surface temperature will rise to about 60 °C, a temperature extreme that will very likely kill off most everything that is alive. (This has not happened in the geological past. But it could happen in the future if all the CO2 that is locked up in the carbon reservoirs was released into the atmosphere).
(7) Summarizing the Points to an Impending Need to Act
To summarize, (1) there is no credible uncertainty as to identifying atmospheric CO2 as the principal control knob that governs the strengths of the terrestrial greenhouse effect; (2) there is no credible uncertainty as to identifying atmospheric water vapor and clouds as the temperature dependent feedback effects whose distribution in the atmosphere is governed by the Clausius-Clapeyron relation; (3) there is no credible uncertainty as to identifying the ongoing anthropogenic increase of atmospheric CO2 as the principal cause for the ongoing global warming.
It is very important to differentiate between those aspects of global climate change that are well understood in terms of basic physics (for example, the increased global warming due to the increase in atmospheric greenhouse gases), and those aspects that are known to be chaotic in nature (the unforced natural variability). The former is predictable, the latter is not.
Supported by this basic understanding of our climate situation, policy makers have now both the compelling need and the full justification to act responsibly and start taking positive steps to begin curtailing the continuing growth in atmospheric greenhouse gases. Sensible action would be to promote energy conservation, impose a true-cost responsibility fee on carbon, encourage alternate forms of energy generation, and continue educating the public as to why all this is necessary in order to best protect our current way of life.
These conclusions are all based on well-tested principles of physics and on direct observational data, and not on arbitrary assumptions or guesswork. As the global temperature continues to warm, more and more thermal and latent energy continues to accumulate within the atmosphere, thus providing more fuel and impetus for stronger and more extreme weather events. This is what can be expected from further global warming. And that clearly seems to be what has been happening as the global temperature continues to increase.
To be sure, there are some important uncertainties regarding global climate change that need to be recognized and addressed. For example, our current best estimates for the equilibrium sensitivity to doubled CO2 are about 3 °C, based on climate GCM modeling results, paleoclimate data, and other available measurements. But, because of the uncertainties in aerosol contribution to the direct and indirect forcings, it is not possible to attribute precisely what fraction of the observed climate change is due only to CO2, based on observational data alone. Because of uncertainties regarding the rate of heat energy mixing into the deep ocean, the time scale of the climate response will also be impacted. In view of this, the current climate sensitivity to doubled CO2 could well be within the range of 2 – 4 °C.
There are also real and significant uncertainties affecting the regional changes of climate that arise from semi-chaotic behavior in horizontal transports of energy, but these have minimal impact on the global energy balance since the horizontal transports, integrated over the globe, must average out to zero. There are further real and significant uncertainties in knowing how rapidly the polar ice will disintegrate in response to the increased warming. All of these uncertainties are real and significant, and they are active topics of current climate research to be ultimately resolved and understood.
However, none of these uncertainties materially alter the fact that the global temperature continues to rise unabated (with some unforced natural variability superimposed), as the direct result of continued increases in anthropogenic greenhouse gases. Policy makers should take heed to act responsibly and start taking positive steps to curtail the growth in atmospheric greenhouse gases. To not act is to continue playing Russian roulette until climate disaster eventually hits home.