Guest Post by Willis Eschenbach
Andrew Lacis and the good folks at GISS have a new paper, Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature, Andrew A. Lacis, Gavin A. Schmidt, David Rind, Reto A. Ruedy 15 OCTOBER 2010 VOL 330 SCIENCE [hereinafter “Lacis10”]. Although most commenters have dismissed their work as being derivative and not containing anything new, I find that they have actually made a couple of unique and novel errors. I have two main difficulties with their paper. I have a problem with one of their theoretical claims, and I also have large issues with their model results. First, the theoretical claim. Lacis10 says:
Because the solar-thermal energy balance of Earth [at the top of the atmosphere (TOA)] is maintained by radiative processes only, and because all the global net advective energy transports must equal zero, it follows that the global average surface temperature must be determined in full by the radiative fluxes arising from the patterns of temperature and absorption of radiation. This then is the basic underlying physics that explains the close coupling that exists between TOA radiative fluxes, the greenhouse effect, and the global mean surface temperature.
Figure 1. Global Energy Budget from Trenberth et al.
Let me examine this claim one piece at a time.
They start by saying:
Because the solar-thermal energy balance of Earth [at the top of the atmosphere (TOA)] is maintained by radiative processes only …
This is not clear. What does “maintained” mean? I think they mean that on average outgoing radiation must perforce equal incoming solar radiation, which is true. As seen in Fig. 1, 341 W/m2 of incoming solar is balanced by the 102 W/m2 of reflected solar plus 239 W/m2 of outgoing longwave.
Next they say:
… and because all the global net advective energy transports must equal zero, …
“Advection” is defined by the American Meteorological Society as “the process of transport of an atmospheric property solely by the mass motion (velocity field) of the atmosphere;”
Since advection merely moves energy around, you’d think that advection wouldn’t change the average global temperature. However, while energy is conserved, temperature is not conserved. Suppose we take two equal areas, say the part of the planet from 30N to 30S (average 25°C) and the rest of the planet including the poles (average 4°C).
Advection (also called “atmospheric transport”) moves about 20 W/m2 from within the tropical and subtropical area of 30°N/S to the temperate and polar area outside of 30°N/S http://www.sp.ph.ic.ac.uk/~arnaud/PAPER/Czaja_Marshall_jas06.pdf. Using blackbody calculations for simplicity, from the 20 W/m2 energy transfer the equatorial area cools by three degrees, while the same area at the poles warms by five degrees. And as a result, the average temperature of the two areas warms by a full degree, simply from advection.
So while the authors are entirely correct to say that the net advective energy transports equals zero, the same can not be said about the effect of net advective energy transport on temperature.
However, let’s ignore that. Let’s say that both of those statements are true for the purposes of this analysis. Given those statements, they then say:
… it follows that the global average surface temperature must be determined in full by the radiative fluxes arising from the patterns of temperature and absorption of radiation.
Here’s where we really part company, on two points. First, surface temperature is not “determined in full by the radiative fluxes”. There are also sensible heat fluxes from the surface to and through the atmosphere (conduction/convection, called “Thermals” in Fig. 1) as well as latent heat fluxes (evaporation and transpiration, or “Evapo-transpiration in Fig. 1). Both of these cool the surface without changing the TOA “solar-thermal energy balance of the earth.” Either I don’t understand their conclusion, or I disagree with it. What am I missing?
Second, there is no logical “it follows” path to get from the two statements
“solar in = solar + longwave out”
and
“net advective energy transport = 0”
to their conclusion
“global average surface temperature must be determined in full by the radiative fluxes”.
I cannot think of, and they do not provide, any logical chain of reasoning that connects the third statement to the first two.
So that’s the theoretical problem with the paper. They claim that the surface temperature of the planet is “determined in full by the radiative fluxes”. I say no.
Next, the model problem. They base all of their claims on making very large changes in the variables of the GISSE global climate model. The model problem is that like many other climate models, GISSE has the cloud feedback backwards. The GISSE model says that clouds are a positive feedback. There’s a good study of the question by De-Zheng Sun et al., 2009, Tropical Water Vapor and Cloud Feedbacks in Climate Models: A Further Assessment Using Coupled Simulations, Journal of Climate, 22, 1287–1304 [hereinafter Sun09].
Among other things, Sun09 says:
A more serious concern raised by the study of Sun et al. (2006) is the finding of a common bias in the simulation of the cloud albedo feedback in the leading climate models: with the exception of the GFDL model, all the models they analyzed in that study underestimate the response of cloud albedo to the surface warming.
This finding from Sun 2006 were reconfirmed in Sun09. Here’s an illustration of the problem:
Figure 2. Solar (albedo) cloud feedback (blue bars), cloud longwave (yellow bars), and net cloud feedback (red bars) in models and observations of the equatorial Pacific (5°S-5°N, 150°E-250°E). Net feedback is the sum of the longwave and albedo feedbacks. Period of study 1983-2004. DATA SOURCE Sun09 Table II. See Sun09 notes for Table I and Table II for details on the data.
Note the errors in the modelled albedo feedback (blue bars). In the tropics, solar albedo feedback works as follows. Increasing warmth means increasing clouds. Increasing clouds means more sunlight is reflected into space. This cools the earth, and is a negative feedback.
While most of the of the models at least get the sign of the cloud albedo (solar reflection) feedback correct (more clouds means less sunshine hitting the earth, a negative feedback), the UKMO Hadgem1 and the GISS EH models don’t even get the sign of the albedo feedback correct. The rest of the models underestimate the size of the albedo feedback, with values as low as 16% of the observed cloud albedo feedback.
There are also a very wide range of values for the longwave, some of which are very small compared to the actual observations.
In addition to the albedo and longwave problems, a larger issue is the net cloud feedback (red bars). All but one of the models show positive net cloud feedback. The observations and one model show negative feedback.
Now, the Lacis10 authors are using their model to determine (among other things) what happens in the deep Pacific tropics when the non-condensing GHGs are removed from the atmosphere.
Obviously, the first thing that would happen if GHGs were removed is that the planet would start to cool. The immediate response in the tropics would be that daytime cumulus would decrease. This would allow more sunshine to heat the earth, which would be a negative feedback on the cooling from the lack of GHGs.
In addition, the number of tropical thunderstorms would decrease. This would slow the Equator-to Poles atmospheric transport. Once again, this would warm the earth, and would also be a strong negative feedback on the cooling.
The GISS model, on the other hand, says the opposite. It says that as the Earth cools from the lack of GHGs, the change in clouds would make it cooler yet … and unsurprisingly, it says that the net result would be that the planet would spiral into a permanent snowball. Fig. 3 is a figure from the Lacis10 paper, showing how they think it would evolve:
Figure 3. Lacis10 description (their Fig. 2) of the evolution of GISSE model when non-condensing GHGs (everything but water vapor) is removed.
I find this graph quite odd. Immediately after the GHGs are removed, surface temperature starts to drop. That makes sense. But concurrently, there is a steep increase in clouds, from 59% coverage to 69% coverage in one year. This doesn’t make sense. A warmer world is a wetter world. A warmer world is a world with more moisture in the air, and a world with more rainfall and more clouds. Conversely, a cooler world is a dryer world, with less clouds. What would cause the modelled clouds to increase in coverage as the earth cooled? This may be related to the reversed sign of the GISS albedo feedbacks shown in Fig. 2.
(In addition, the GISS Model E normally shows about 10% less cloud coverage than the real Earth. See Present-Day Atmospheric Simulations Using GISS ModelE, (PDF 2.2 Mb), page 169.)
Finally, Fig. 4 shows the atmospheric transport feedback and the total atmospheric feedback, again from Sun09. This is the net cloud feedback shown in Fig. 2, plus the water vapor feedback and the atmospheric transport feedback. (Water vapor feedback is similar in observations and models, and is not shown.)
Figure 4. As in Fig. 2, for atmospheric transport feedback (blue bars) and total atmospheric feedback (red bars). Total atmospheric feedback is the sum of the feedbacks of water vapor, cloud longwave, cloud shortwave, and atmospheric transport. Fewer models are shown than in Fig. 2, because of lack of data for the remainder. See Sun09 for details.
As with the net cloud and the cloud albedo feedbacks, the atmospheric transport feedback is also underestimated by many models. Atmospheric transport is the movement of energy out of the Equatorial area of the study. This transport of energy out of the area increases as the temperature goes up, so it is a negative feedback. It reduces the size of an expected increase.
And as a result of all of the model underestimations, the net feedback for the observations is much larger than any of the models. And indeed, some of the models go so far as to claim positive feedback in the deep tropics area studied.
So that’s my second problem with the Lacis10 paper. Given the huge variation in the feedbacks of the different models, and given that all but one of them show positive cloud feedback in the tropics, there is absolutely no reason to place the slightest credence in the GISS ModelE results reported in Lacis10. Let me close with this quote from James Hansen, pp 2-3 (bulleting mine):
2.4 Principal Model Deficiencies [of the GISS ModelE climate model]
Model shortcomings include
• ~25% regional deficiency of summer stratus cloud cover off the west coast of the continents with resulting excessive absorption of solar radiation by as much as 50 W/m2
• deficiency in absorbed solar radiation and net radiation over other tropical regions by typically 20 W/m2
• sea level pressure too high by 4-8 hPa in the winter in the Arctic and 2-4 hPa too low in all seasons in the tropics
• ~20% deficiency of rainfall over the Amazon basin
• ~25% deficiency in summer cloud cover in the western United States and central Asia with a corresponding ~5C excessive summer warmth in these regions.
I mean, how could you not trust a model with specs like that?
w.
Why do I get the feeling that they’re trying to fit reality into their hypothetical modeling.
It occurred to me a while back that heat from the Earth’s mantle must pass through the crust at a certain specific power. It seems that this effect is trivial – 0.2 W/m2 – compared to solar, and doesn’t merit being included in the equations.
The IPCC claim that “black carbon on snow” contributes just 0.1 W/m2, but this figure is not absolute: it is a relative change compared to its pre-industrial value, and therefore not comparable to the 0.2.
Might it be that the moon’s tidal effect might oscillate, contributing a few tenths of a Watt of variation on a decade/century timescale? No? Ah, well, I’ll get me coat.
‘Knobs’ indeed….. Perfect!
Thanks for the post and analyses, Willis!
Strikes me as something that the peer reviewers should have offered before publication. If they did, what was the result? In any case, now that the paper has been publicly peer-reviewed, what are the chances the lead author will respond, preferably here?
This also tells us something is seriously wrong with the existing peer review system.
Knobs were discovered by the previous Administration.
Neither can I Willis. That statement makes no sense physically, and wouldn’t pass muster in a physics paper. First, heat does move around on the surface and can in fact redistribute itself in the ocean, or through rivers and lakes into the ocean. In short, energy contained locally on the planets surface and oceans can change outside of radiative flux. This means the temperature can change due to something other than radiation.
I also do not believe the upper atmosphere is wholly protected from escaping earth’s gravity from the pull of vacuum/solar wind. It is entirely plausible to my mind (and I thought there was literature backing me up but I cannot quote it) that gases/ions actually do escape earths gravity well much as gasses bleed off of comets who venture too close to the sun. I recall a paper demonstrating a picture of earth’s gas “tail” as it were. This is a form of heat transfer to space and it is not radiative. My understanding is that Earths atmosphere is not a perfect bubble, but a leaky bubble that is replenished with vulcanism. Without volcanoes, we would slowly lose net CO2 in the air, which would kill the plants, which would then kill us. This makes me very thankful for Krakatoa. I’m hoping there’s a geologist/space-science person on this thread who can back me up, but I’m fairly certain this is the case and it undercuts the idea that the only heat transfer to space is radiative.
“Principal Control Knob Governing Earth’s Temperature” This title is a gift. It’s astonishing that a paper using this metaphor by these scientists is appear so late in the day. We really do have thermostatic control over global temperature! The scientists (still!) say so.
We can determine our destiny, avoid catastrophe, if we only mend our ways, if youse all do what we say. While there were no control knobs in the 15th century, still its shades of Savonarola versus the Florentine Renaissance, demanding the Bonfire of the Vanities and all that.
Their logic is full of holes. As EthicallyCivil pointed out net advective energy transport does not equal zero. This method dominates in the lower troposphere but both are always occurring at every altitude. Mass flows at low altitudes will lose more energy to radiative fluxes at higher altitudes. Some energy picked up at low altitudes via advective flows will be lost to radiative fluxes at higher altitudes. This seems obvious, what am I missing?
The temperature v energy issue is important too. The specific heat capacity of water is about 4 times that of air. Now consider the specific volume differences and you realize that you can heat many cubic meters of air using the energy contained in very little water and cool the water much less than the air is heated. Assuming of course that the temperature difference exists to transfer the energy. And I haven’t even begun to discuss latent heat.
Because energy can be neither created nor destroyed. So all you are doing with advective transfers is moving it around, and what one place gains, another loses. Net zero.
Thanks, Anthony. I finished the essay at about 3:30 AM last night, then posted it in a hurry this morning …
And while I’m here, thanks also for:
• Having the best and freest science blog on the web. The moderation is generally very light (although repeat offenders may get banned after repeated warnings). The tone is good and is improving, hopefully even mine. And the science is always welcome, whether it is agreed or disagreed with.
• Allowing me to post here under my own by-line without any pre-screening or editorial changes. Much appreciated. People should know that Anthony and I don’t always agree about the science. However, he gives me free rein to make my own inimitable mistakes and curiously probable claims, without interference or hindrance. He is clear that I do not speak for him, nor he for me.
So my thanks for all of your efforts, my friend.
w.
IR radiated at higher altitudes, above the majority of greenhouse gases is less likely to be absorbed by the thinner atmosphere on the outward vector than the denser inward vector. For air carried aloft, the net flow of radiated energy is outward.
The premise that convecion/advection does not contribute is false.
it is a spinning ball for Gods sake; the temperature goes up and down during the day and night cycle, the system is never in a equilibrium state. What absolute crap this paper is.
“Because energy can be neither created nor destroyed. So all you are doing with advective transfers is moving it around, and what one place gains, another loses. Net zero.”
Not net zero….energy radiating into space is not destroyed, it simply does not return to the atmosphere. A net loss.
Willis,
But can’t energy be transferred into a fluid via conduction and convection and transferred out via radiation? Or am I misinterpreting what is meant by advective flows?
According to the simplistic Trenberth diagram displayed by Willis, the proportions of various HEAT sources leaving the surface are:
Evapo-transpiration = 49.7%
NET Radiative, absorbed in troposphere = 35.2%…. Direct to space = 3.5%
Thermals = 10.6%
Net absorbed by the surface = 0.9% (what a travesty!)
Thus, by far the greatest HEAT loss contribution (which is 99.1 % of the total HEAT in), is given as from evapo-transpiration (E-T).
There is much debate about feedbacks from clouds arising from cloud cover changes. There is also positive feedback argued for increased water vapour in a warming world. These two parameters would appear to be related to E-T, so it seems to me that a necessary small % change in E-T would have a greater cooling effect than the radiative effects of clouds and water vapour
I’ve asked Roy Spencer about this, and he agrees that it is important, but without suggesting how much so. He has not responded to my latest Email but the message I seem to get so far is that everyone is too busy arguing the radiative effects to even think about what would seem to be a larger negative feedback in E-T (evaporative cooling + latent heat)
Regardless of what happens at TOA, the measure of global warming over the past 150 years IS ONLY given by the near surface temperature. That temperature is affected by what happens at the surface and in the troposphere, but not so much at TOA.
Thoughts anyone?
“knobs” … misleading title… I thought it was going to be an article about bumbling UN politicians, who people of British descent would rightfully describe as knobs.
Thanks, Willis, I always enjoy trying to follow the thoughts in your articles. I have three points that I would like to make about atmosphere temperature control knobs. I found chart at NOAA showing that humidity in the upper Troposphere has been decreasing continuously since 1958. Studying the chart, I concluded that increasing CO2 would result in displacing H2O vapor into outer space due to simple partial pressure equilibrium. This would act as an atmosphere temperature relief valve.
My second point is the amount of ground water from slow to recharge (fossil) aquifers grew continuously from about 1945 to about 2000 or so. The large bulk of this water is used for crop and forage irrigation. The aquifer levels have started dropping, especially in US, China and parts of India who are the big players in irrigation. The levels have dropped to the point that production rate has been to slowly drop as well. The amount of produced water that does not recharge back into the earth is about 800 cubic kilometers per year. This amount of water raises the ocean levels about 2.6 mm per year. The evapotranspiration of the produced water on the surface changes the potential energy of the water into kinetic energy at constant temperature due to latent heat. The water vapor rises until it is reaches condensation temperature where the kinetic energy releases specific heat into the atmosphere as it changes back into potential energy. Thus, the condensation increases the temperature of the atmosphere more than enough to account for the observed global warming.
My third point is the number of continuously operating evaporative cooling towers also began to increase about 1945. These towers force or induce air into contact with water falling down the tower. The evaporation of water into vapor causes the water to cool for recycling. The air expelled from the top of the cooling tower is essentially 100% hot saturated air and aerosols, which rise to form clouds.
These are real operational activities at work day in and day out. Hansen et al seem to me to be missing real contributors to changes in the climate.
“Using blackbody calculations for simplicity, from the 20 W/m2 energy transfer the equatorial area cools by three degrees, while the same area at the poles warms by five degrees.”
Willis, this touches on a problem I have with climate models generally. Trenberth was quoted, at Lucia’s I think but possibly at Judith Curry’s, as saying that the climate models run at a range of absolute temperatures; and as I recall, most run hotter than the actual world. However, the argument is made that it is the anomalies of these models which are predictive of climate change. But, thermodynamically speaking, as your quote above demonstrates, the amount of temperature change from a given amount of energy input depends on the temperature at which the input occurs. Thus your tropical zone decreased in temperature by 3 degrees while the much colder polar regions increase in temperature by 5 degrees, from the same change in energy. So, how can models running at different temperatures from the real world and each other have the same trend from the same increase in CO2 forcing? Surely the hotter models should have a lower trend and the colder models a higher trend?
TOA for the “atmospheric window” is the surface. Every molecule emitting in that range will cool without limit. It will “steal” heat from adjacent molecules, and keep pumping it out the window. Thus the window becomes the “preferred” radiative exit for energy from the surface, since none of the photons at those energies is bounced or “back-radiated”.
Willis,
Thanks for the informative post. One small comment, you started by saying “I think they mean that on average outgoing radiation must perforce equal incoming solar radiation, which is true.” This is not necessarily true at all, it would strictly be true only if the earth and sun were in equilibrium with each other, which of course they are not (sun 6000K, earth 300K!) . If the sun were to disappear tomorrow, there would be no incoming radiation, but the earth would still radiate out. I guess it’s observed that there is roughly an incoming/outgoing balance in practice, since the earths mean temp is roughly constant, but there is no a priori reason for this to be true.
Jeremy;
Aside from solar wind knocking molecules out, out, and away, there is always going to be some loss from thermal evaporation (individual molecules achieving escape velocity due to chaotic Brownian motion effects.) Probably electromagnetic acceleration of ions gets involved, too.
I.e., there’s more than one “leak” in the balloon.
Slightly OT but maybe Willis can clarify:
The energy budget diagram shows 78W/m^2 of incoming solar energy being absorbed directly by the atmosphere. Is half of this then included in the outgoing and half included in ‘back radiation’?
Doesn’t this bugger up the theoretical amount of radiation trapped by the atmosphere from outgoing LW from the surface?
The analysis of Willis Eschenbach is correct and shows one of the essential errors done by many climate scientists, in that respect that they believe that the mean temperature of the Earth is a proxy of the global warming. Though it sounds paradoxical, the earth can be warming/cooling despite that mean temperature of the Earth is falling/rising.
The first statement of Lacis et al, that global spatial average of advective energy (convective power flux) is true and zero per definition. But as Willis has pointed out the next part of the statement is not correct:
….it follows that the global average surface temperature must be determined in full by the radiative fluxes arising from the patterns of temperature and absorption of radiation.
The mean global temperature is computed as a spatial and temporal averaging of the local measured temperatures, which locally is determined by the in/out going radiation and the convective power flux. Averaging this does not remove the convective power flux (the advective energy). The reason for this is that in a local radiation balance the temperature dependence is a complicated function. The dependence goes approximately as the fourth power of the temperature (Bolzmann). So an averaging of the radiation balance will give the mean value of the forth power of the temperature and this will be independent of the convective power flux. But this does not give the mean temperature of the Earth. However it would be a good proxy of the global warming/cooling issue i.e. computing the spatial and temporal averaging of the fourth power of the temperature and expressed it as an equivalent temperature i.e. as the cubic root of the measurement. I would expect that a global curve of these equivalent temperatures would appear to be much less fluctuating than the present representation of global temperature.
The (local) climate and the temperature are determined by the convection in the atmosphere and the oceans. So only if there is a coupling between the convection patterns and (minor) changes in the radiative power flux due to greenhouse gasses, the climate will change of this reason. But this has to my knowledge never been proved.
Thank you for that fascinating study by Evans, Dave. Lacis (above) claims that
In the Evans clear-sky observations (no clouds) CO2 was measured at 11% of the total downwelling radiation from water vapor, CO2, and minor GHGs.
In the Lacis10 study CO2 was 27% of the total of water vapor, CO2, and minor GHGs. In other words, the Lacis10 computer results show about two and a half times more radiation from CO2 (and minor GHGs) than Evans’ observations.
Alternatively, we could approximate the clouds. In Lacis10 clouds have half the forcing of water vapor. We can apply this same percentage to the Evans observations, and assume that the clouds are half of the water vapor forcing. This increases the total forcing by that amount.
This (naturally) reduces CO2 forcing as a percent of the now-larger total. In this case, which is comparable to the Lacis formulation above, CO2 is 8% of the total, with the minor GHGs at 2%.
Once again, the Lacis10 results are about two and a half times larger than the Evans observations.
The other finding of Evans was that more water vapor in the air means less CO2 absorption in both absolute and relative terms. In the winter it was measured at 105 W/m water vapor versus 35 W/m for carbon dioxide (33%). In summer CO2 radiation goes down to 10 W/m2 versus 255 W/m2 for water vapor (4%), due to increased absorption by water vapor.
This means that CO2 will make less difference in the tropics, with its uniformly high humidity, than in the extratropics where the Evans observations were taken.
So no, I don’t find the Lacis10 invocation of the GISS ModelE death spiral into terminal Arcticatastrophe at all suasive …
I don’t understand. Why are all the models that disagree with observation, at least in quality, if not quantity, not thrown away as innacurate or just plain wrong.