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.
mkelly says:
December 10, 2010 at 7:34 am
Just on a photon to photon basis many more IR photons must leave to make up for the decrepency in energy levels. But where did the extra ones (photons) come from?
Lets be clear, photons are bosons, i.e. they have integer spin (1). There is no conservation of bosons law, there can be as many as needed to obey the energy conservation law.
@willis
“The loss of the GHGnc gases gives only a 9 W/m2 change in downwelling radiation, according to MODTRAN. While this is a significant change, it is far from enough to send the planet spiraling into a snowball.”
Yet a mere 2 degree change in axial tilt creates or melts a continent size glacier that buries everything north of Washington DC under a mile of ice.
Don’t make claims you can’t back up.
Ron Cram says:
December 9, 2010 at 10:29 pm
“A warmer world is a drier world.”
That’s as wrong as wrong gets. The driest place on the planet by far is Antarctica.
Owen, you are making the faulty assumption that radiation can only be absorbed once on the trip from surface to the stars. In reality, it can be (and almost certainly is) absorbed and re-emitted multiple times (like a distillation tower), thus while each stage has a 50% chance of emitting up or down, the “50% maximum” that you mention doesn’t exist.
anna V.
I’m refering to the approach of measuring they used in that paper. Not the specific conclusions they draw or assumptions they make.
The hand that twirls the Knob that sets the dial on the Magic Thermostat rules the world! Cradles-rocking is merely second-best.
Ben of H;
Since the proportion of energy that gets re-emitted by ‘fingerprint’ radiation (as opposed to lost through thermal conduction, etc.) is very low, the log decline at each stage means the final total % is likely very close to 50.
It doesn’t. Venus emits quite a bit more energy than it gets from the Sun (almost none of which makes it past the upper cloud decks anyhow, thereby eliminating, by definition, any GH effects). There is evidently a considerable heat engine or pool still at work in Venus’ interior.
Something about the advection statement just doesn’t make sense. Yes, if you consider ONLY advection in the sense that mass is advected back and forth but the net mean atmospheric air density is unmodified, then that’s correct. But as the author pointed out, IF you are talking about HEAT, it is an entirely different matter. If I draw a line at the 30-degree North latitude and ask whether there is a net advection of heat across that line then I would certainly say that there must be. Warm air moves north and cold air moves south and there is a net loss of heat from the equatorial region. Certainly Lacis et al. know this. Then why are they making this baseless claim?
By moving warmer air north the air temperatures in the north must increase by some delta-T while those to the south decrease by an equal amount, since Temperature is a quantity proportional to the mean kinetic energy present, it is a direct measure of energy content. But by increasing the temperature of cold air, the net increase in the outgoing longwave energy is not linear in dT. Rather, due to the T-to-the-4th power in the radiation equation, a dT temperature change produces (roughly) a 4-dT/T effect.
The Lacis et al. static analysis thus discounts the very mechanism that would modulate the environment. The warmer air moving north over colder seas causes increased evaporation and greater cloud cover. On the flip side, if for some reason the Earth were to start cooling, there would be a removal of energy and thereby a reduction in the energy transport mechanism. The result would be to reduce cloudcover, as indicated, but also maintain an island of heat near the equator. The increased gradient would thereby keep the Earth from further cooling, limiting the impact of any ice-age.
Thanks muchly for that post. I’ve been keeping an eye open for a comprehensive themodynamic summary statement like that.
Brian H – I agree with you.
Therefore, the original premise is nonsense.
QED ?
anna v says:
December 10, 2010 at 8:10 am
Lets be clear, photons are bosons, i.e. they have integer spin (1). There is no conservation of bosons law, there can be as many as needed to obey the energy conservation law.
I guess I should have put a smiley face after the question. My point is the energy coming in is based on frequency of light from the sun. The frequency of IR per example gives energy 20 times less.
1 mole = 22.4 liters
1 m3 = 44.6 mole
1 mole = 6.022 x 10^23
44.6 x 6.022 x 10^23 = 2.7 x 10^25
2.7 x 10^25 x 3.58 x 10^-19 = 9666000 J s per m^3 sun light in
2.7 x 10^25 x 1.32 x 10^-20 = 356400 J s per m^3 IR out
I am not convinced that W/m2 is the best way to show the energy balance.
Yes I know there is no real mole of photons it is an example only to show a differnce in energy.
mh;
yes, the analogy I’ve come to is that of a pressure vessel, with one leak or outlet. As material (energy) is forced through the gap, it is rapidly replaced and followed by more from the rest of the volume. The outflow thru that gap is thus far higher than if there were multiple simultaneous outlets.
Am I misconstruing the situation?
Mars is a better place than Venus to see that CO2 doesn’t really contribute much in a radiative way to the so-called “greenhouse effect” (which was even noted by Lacis et al. in this current paper we’re discussing).
Mars’ atmosphere is 95% CO2, so in spite of the low air pressure (1% of Earth’s) there is about 30 times more CO2 per unit surface area on Mars than on Earth. Yet the mean surface temperature is the same as the black body temperature, ~210 K, according to NASA’s “Mars Fact Sheet”:
http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html
Black-body temperature: Mars 210.1 K Earth 255 K
Average temperature: Mars ~210 K Earth 288 K
Other sources sources might quote slightly higher mean Mars temps, but only a few degrees warmer at most. I use NASA’s Fact Sheet figure, because they computed it before the AGW era, from the old Mariner mission spectrometry analysis, and probably contains less bias than any modern “calculations” they might have produced since then. [Yes, I don’t trust them now.]
Lacis et al. don’t offer any detailed explanation of this deficiency, but suggest it might be due to “pressure broadening” of the CO2 absorption lines. I’ve seen that claim by other AGW apologists, but have not found any substantive explanation of how line broadening (in Earth’s high pressure atmosphere) ‘enables’ the CO2 GH effect on Earth but not on Earth. I’m skeptical, sounds like hand-waving to me. (But please correct me if this is a well-understood mechanism.)
So what does account for the 33K “comfort blanket” that we enjoy on Earth? I think we all know the answer: it’s the water, in all of its physical states, that captures and regulates this additional warmth that has made life possible on Earth.
I should have been more pointed about why I dislike the 2D Global Budget chart.
Energy doesn’t translate to temperature. Altitude is a good example — same amount of energy but decreasing temperature. Space would be another reasonable example. Night is another – no solar input yet only a marginal drop in temperature.
The budget chart implies a static global effect that isn’t static or global.
Isn’t the surface temperature trend in Antarctica another good example of the Not Global aspect of the Greenhouse effect?
http://earthobservatory.nasa.gov/IOTD/view.php?id=6502
anna v says:
December 10, 2010 at 8:10 am
Massless!
John Kehr points out above that the Trenberth diagram illustrated by Willis can be misleading. It crudely attempts to show the greenhouse effect giving large numbers for surface radiation and back radiation. However, this radiation, or more properly Electro-Magnetic Radiation (EMR) is not HEAT. Furthermore, HEAT transfer via EMR is determined by the difference between opposing EMR, and in the case of the Earth, here is another NASA diagram that only shows net HEAT transfers. EMR also radiates in all directions, so that most of it is tending to be lateral rather than straight up and down as illustrated by Trenberth. Yet, in any typical homogenous layer of air, obviously, there is no lateral HEAT transfer, no matter how intense the lateral radiation is
This NASA diagram has slightly different net values and descriptions to Trenberth’s latest version, but it illustrates the point about net heat loss from the surface:
Evapo-transpiration (E-T) = 45.1%
Net EMR absorbed by atmosphere = 29.4% And directly to space = 11.7%
Convection = 13.7%
Thus, the greatest proportion of heat loss from the surface is via E-T, which presumably is the driver for water vapour and clouds, which are widely debated for their radiative effects in feedbacks. However, there seems to be no interest in the significant negative feedback which should arise from a small proportional increase in E-T.
Willis Eschenbach says:
December 10, 2010 at 1:28 am
Willis, I have been working with control loops for 35 years now. What often is observed is that many people are fooled by cause and effect ; They often draw the opposite conlusion of what is going on in such a loop.
The warmers have got it the wrong way around. You got it right.
Slowly this will be discovered. I think the warmers already know it in their hearts. But it is hard to accept.
Andy and pals got the title of their paper wrong. It should have been Atmospheric CO2: Principal Control Knob Governing Giss Model E’s “Temperature”.
“Principal Control Knob Governing Earth’s Temperature”
I could tell you who that control knob would be, but he doesn’t govern the Earth’s temperature.
As a “thought experiment” move the Earth closer to the Sun. At some point most of the Ocean would become atmosphere (give or take a bit of supercritical nonsense) . I have no idea what the atmospheric pressure of 1.4 billion cubic km of water equates to, but it could just be crushingly “wetter”
As an additional “thought experiment” move the Earth away from the the Sun…. Oceans of Nitrogen and no atmosphere to speak of.
Miskolczi, Ferenc – molecules defying gravity must get their gravity defying energy from somewhere. If energy into the system is constant then …
So how far towards the equator do glaciers have to go to get runaway cooling in the models? How do they extract themselves from ice ages?
I think you and others misunderstand what Lacis10 said. Advective energy transports indeed must equal zero. If you are moving energy from one place to another, what one loses the other gains. Net zero. As I pointed out, while energy is conserved, temperature is not.
Willis Eschenbach says:
December 10, 2010 at 1:28 am
Baa Humbug says:
December 9, 2010 at 12:19 pm
Thankyou for the reply. I allus learn somfin from ya
Willis,
I don’t think anyone is confused on conservation of energy. That is not the question. Every reference to advection I can find speaks of a mass flow. Radiation heat transfer must be included when considering conservation of energy. Mass flow is not required for heat transfer via radiation. Some of the references I have seen regarding advection appear to me to be talking about what I have traditionally referred to as forced convection. Such as energy transfer due to mass flow of the wind.