In the article copied below, Roy Spencer makes the valid point that there are many "feedback" factors influencing climate heating which aren't factored in by "climatologists" and other missing link descendents of the alchemysts.
This doesn't even begin to scratch the surface. It's so commonly glibly stated that "clouds trap heat". They also *reflect* it back from the sun. Less heat gets down to Earth. But hotter climate would create an increase in the number of clouds, reflecting more heat, hence, reducing the temperature rise that would otherwise have occurred, diminishing cloud production, etc. A pretty strong feedback loop. Global temperature rise *always* has to increase the average level of atmospheric humidity, but only small increases in the humidity have to increase the clouds. Self-regulating. I have long suspected that this is far more dominant than any alleged "greenhouse" gases and that the loop gain of the feedback is so high that Earth's average temperature (whatever that means) can change very little, even for fairly substantial increases in solar radiation.
If you think about it, do an analogy between the Earth and your house. Let's say you built a glass house (all climate researchers live in glass houses) with double-pane windows to trap the heat inside. Think "glass geodesic dome". Now, I think I can say with confidence, those glass panes are probably at least as good if not better than the Earth's atmosphere (adjusting for scale, of course) in "trapping" heat. They usually use Argon gas to retard the transfer of heat from inside to outside, and while the mechanism isn't the same (thermal transfer via gas diffusion instead of by re-radiation, though the windows in *my* house also have a special plastic film that actually reflects infrared), I think the analogy is useful:
If I changed the Argon concentration in this glass house by the fraction that global warming whack-jobs claim mankind is increasing CO2 in the atmosphere (about doubling), how much would my winter heating bill go down?
NOT. Not much, anyway. I just paid a $302 gas heating bill for November. I suspect it would go down about 0.1%, or 30 cents. If that. That is, look out your windows in this glass house, and ask, if I increase the gas between the panes by 0.5% does it block much more heat going out? NOT.
Actually, as I think about it, my gaseous diffusion analogy is good. Even the Earth radiates by gaseous diffusion, at least, from the surface to the upper atmosphere -- even if there *was* a layer of CO2 to "block" the infrared radiation from Earth, the jostling of air molecules would transfer heat *past* the CO2, up to the upper atmosphere, allowing the heat energy to radiate into space anyway. This, I think is the proof that the CO2 theory is completely, totally bogus. Geez, I'm smart.
My point, as obscure as this analogy is, is that I doubt the CO2 in the atmosphere has any truly significant effect on the overall global temperature. The vast majority of heat that the Earth receives is what gets past the clouds to reach the Earth and heat it up -- but there *has* to be a balance of "what goes out (re-radiated back to space) = what comes in (from the sun)". The total solar efflux of heat is so great that whatever little CO2 there is in the atmosphere (something like 0.5%, if I recall correctly) can have only a miniscule effect on the heat balance, whether by clouds dominating, or by gaseous diffusion bypass. A lot less than the 1 - 3 degrees (or 100 degrees if you watch "The Day After Tomorrow's Most Stupid Environmental Scaremongering Doomsday Film of the Century").
Put it another way. The Earth is a "blackbody radiator", in the parlance of science. A fact widely used in science and space engineering, by the way. For you non-scientists, have you ever huddled next to a hot boulder on sunny day with a cold wind? That's Earth. Third hot rock from the sun. All that solar radiation is heating us up and we're all huddled next to the rock to keep warm. But the rock radiates back into space. The atmosphere might provide a little thermal insulation, but not much. (Certainly not like a good thermos bottle.)
But the enviro-whackoists are claiming that by wrapping a hot rock in a little CO2 that the Earth is going to have be insulated from radiating the sun's energy back into space. Meaning, higher surface temperature would be required to radiate into space the same amount of energy as the Earth is receiving from the sun. Like, if you wanted to feel the outside of that thermos get warmer, you need to put hotter coffee inside.
But putting aside alleged CO2 reflection of infrarad from the surface, how much insulation does the atmosphere provide? A thin amount. Wrap yourself in a 1mm air blanket and go outside in January in Minnesota on a sunny day. The only thing keeping you warm will be the solar radiation your body receives directly.
Actually, here's another nail in the coffin of the CO2 theory: Putting aside the fact that Earth will ultimately re-radiate even "trapped" infrared by gaseously diffusing heat (molecules bumping into each other) from the lower to the upper atmosphere (ie, right around and CO2), the effect of the CO2 itself has got to be small. If it's reflecting heat going up, it's reflecting heat coming down. Now, the standard explanation is that on the way down the wavelength of the sun's energy is higher on average than what's going up, and there's some truth to that, but it can't be that much different. The Earth is a blackbody radiator. Whatever energy gets absorbed and then re-radiated is going to have a spectrum not that much different than the Sun's, even though the sun is much hotter. Yes, there's a shift towards lower frequency cause the Earth is cooler than the sun (about 6000 degrees cooler), but the famous Planck radiation formula shows the frequency shift is not that much.
MOREOVER, if you look at charts of atmospheric absorption versus wavelength (or frequency) the trend is clearly that at longer wavelengths the atmosphere becomes more transparent. Lousy absorption. That's why radiowaves travel so far, but you can't see nearly so far even on a nice haze-free day. (Nate, don't grimace at my science. A little literary license is needed here.) So you can say that on average, the shift in energy from shorter wavelength (ie, higher frequency) from the sun, to longer wavelength (ie, lower frequency) from the hot rock Earth, should allow that heat to radiate away more efficiently, the atmosphere be damned.
Of course, the atmospheric absorption (I've got pretty graphs if anyone is interested) does have many "absorption lines", where particular gas molecules will "resonate" and absorb energy more efficiently. The global warming psychos (I will run the gamut of insulting names for them, probably ending in "scientific pedophiles" and "serial killers of rational thought") claim that it is atmospheric absorption at certain of these spectral lines that "captures" the heat so efficiently. So, these lunatic advocates of fake science that is worse than animal bestiality claim, CO2 absorbs certain frequencies of energy radiated by the hot rock, and *doesn't* absorb the frequencies coming from the sun. So what comes in heats the rock, but what the rock re-radiates gets trapped.
What a crock of rock, now that I think about it even more. The first question to ask, is: what *fraction* of what is re-radiated by the hot rock is around the wavelength at which the CO2 absorbs. Not Too Damned Much. Those atmospheric absorption lines are damned narrow. I forget the actual wavelengths for CO2, but I think it's around 10 microns. Translate to frequency, estimate the linewidth of CO2 (probably 1/1000 of the wavelength, integrate Planck's formula, and presto, hey! I bet you find the total energy that is absorbable by atmospheric CO2 is maybe 1/1,000,000 of what's re-radiated by the Earth. A guess, but my guesses are often pretty damned good when subsequently verified. (And when they're not so good I crawl into a hole in the ground and hibernate during the Nuclear Winter of my dis-contempt.) This is the fraction of solar energy that the CO2 would be trapping, and the fraction that small increases in atmospheric CO2 would be increasing.
Because the *second* question is, what fraction of the 10 micron CO2-absorbing wavelength (if that's what it is) does the atmospheric CO2 actually trap. Ain't gonna be 100%. Some's getting past, like a hockey goalie with a broken stick and a 4 foot hole in his net. Let's pick a number. Say, 10% gets absorbed. Maybe it's better than that, but I like the number. (That's the approach of the climo-scatologists, so why can't I do it, too?) Now you double the amount of CO2 in the atmosphere. How much more gets trapped? Well, it's not linear (there's an exponential for the attenuation), but to first order I think we can assume it is. We'll say twice the heat in that narrow CO2 linewidth gets trapped. Now, instead of trapping (by reflection alone!) 1/1,000,000 of the solar energy in that linewidth, it's trapping 1/500,000.
Big deal. How much could Earth heat up? At a mean surface temperature of 292 degrees (a nice day), the day gets warmer by 0.0005 degrees. No reason for air conditioning and the disaster movie doesn't make a dime.
But it's actually not even that bad. The CO2 reflects the IR at that linewidth... so it goes back to Earth (that little bit of energy that would otherwise have gone to space). What does it do there? It has to heat everything up a little more (0.0005degree). Then what happens? That energy gets spread over a wider spectrum (the essence of blackbody) and then re-radiated again over many more frequencies, with only a small fraction at the frequency you originally absorbed. The Earth has to heat up oh-so-slightly to increase the radiation rate back into space to overcome the reflection of the CO2. Damned little increase by the 1/500,000 standard, but practically, even less.
For this reason (third question): a lot of that reflected heat (a lot of a very little, that is) goes into heating the other 99.5% of the molecules in the atmosphere. Now, heated up a little more, they start jostling amongst each other like a bunch of drunken girls and boys at a college frat party, and they transfer energy (via jostling, not radiation) right on past the CO2 (getting past some kind of chaperone in this idiotic analogy). Once past (into the upper atmosphere) they have time now to re-radiate and voila, most of that 1/500,000 energy originally reflected by the CO2 now radiates into space anyway, without ever heating the Earth up nearly as much as 0.0005 degree. Maybe only heating it up 0.000005 degree.
Grossly oversimplified in detail and just as frightening as "Day After Tomorrow" in its lack of mathematical and numerical rigor, but I hope you can see that the essence of the analysis is utterly correct in principle. You need not fear global warming. Unless the sun heats up too much. Supernovae, whatever. Then you won't care, though. And probably will never know fast enough to care. But I digress.
Raining on the Global Warming Parade
By Roy W. Spencer Published 03/09/2004
There are many remaining scientific uncertainties that limit our ability to predict how much global warming can be expected due to mankind's use of fossil fuels. The largest uncertainties are related to feedbacks. Feedbacks describe how various elements of the climate system respond to an initial warming tendency, and possibly change it. This warming tendency is caused by increased trapping of infrared radiation in the atmosphere from increasing concentrations of carbon dioxide.
Feedbacks can either be positive (amplifying the warming), or negative (reducing the warming), and exert a potentially huge influence. In theory at least, they make the difference between benign warming (say, 1 deg F), or strong warming (say, 7 deg. F) over the next 100 years. Most feedbacks involve water in one form or another. Water vapor, clouds, snow cover, sea ice, and ocean circulations are the major players usually researched.
I believe the largest uncertainty, though, is one that receives little attention -- maybe because we know so little about it. That is precipitation, the only process that removes water vapor (Earth's major greenhouse gas) from the atmosphere. Since water vapor accounts for 80%-90% of the Earth's natural greenhouse effect, it is critical to understand what processes determine its equilibrium value in the atmosphere and how they might change with warming.
All of the water vapor that is being continuously evaporated from the Earth's surface must eventually return to the surface as precipitation. The climate system strikes a balance, allowing only so much water vapor to accumulate before it is depleted by either rain or snow. The term used to describe this self-limiting process is "precipitation efficiency," which is a measure of how readily precipitation processes in clouds convert cloud water into droplets large enough to fall to the surface. Theoretical research has shown that for a given amount of sunlight, high precipitation efficiency leads to cool, dry climates and low precipitation efficiency leads to warm, moist climates .
All of the dozen or so leading computerized climate models increase the amount of water vapor in the atmosphere, significantly resulting in a doubling of the warming that might be expected due to increased carbon dioxide alone. The absolute water vapor increase is such that the relative humidity remains about constant with warming. This is strongly positive water vapor feedback. But how could these models have any credibility on this issue unless they contain knowledge of how precipitation might change with warming? I believe that they can't.
What does the current climate system tell us about this issue? In the tropics, where more sunlight causes warmer conditions, there is indeed more water vapor in the lowest part of the atmosphere (the "boundary layer") than there is outside of the tropics. By itself, this suggests a positive water vapor feedback. But above the boundary layer, the tropical free troposphere has only slightly more water vapor, and much lower relative humidity, than at high latitudes. This wasn't widely realized until Earth-orbiting satellites gave us a global view of the relative humidity field, revealing large regions with RH below 10% in the tropics . And it is this dry, free-tropospheric air that allows huge amounts of Earth-cooling infrared radiation to escape more readily to space. Deep tropical rain systems are apparently more efficient at keeping the free-tropospheric vapor at very low levels, even though the relative humidity near the surface remains nearly the same as that at high latitudes.
The processes which control precipitation efficiency are not well understood. On a theoretical level, we still don't even understand what initiates rain formation in clouds. We do know that precipitation proceeds by larger drops falling faster and growing by collecting smaller, more slowly-falling cloud droplets. But we don't know how the small and large droplets got close together in the first place. Turbulence within clouds probably plays some role.
Unlike the old adage that two wrongs don't make a right, climate models contain many processes that are probably wrong (or non-existent), but are tuned to get the right average climate conditions. So models can be tuned to reproduce the very dry tropical free-tropospheric seen in nature. But this doesn't mean that they contain information on how precipitation efficiency changes with temperature. We need to know how these precipitation processes in clouds change with warming, not just their average values, before we can have much confidence in global warming predictions. And as Joni Mitchell sang in her hit "Both Sides Now", we still "really don't know clouds at all."
1. Renno, N.O., K.A. Emanuel, and P.H. Stone, 1994: Radiative-convective model with an explicit hydrologic cycle, 1: Formulation and sensitivity to model parameters. J. Geophys. Res., 99, 14,429-14,441.
2. Spencer, R.W., and W.D. Braswell, 1997: How dry is the tropical free troposphere? Implications for global warming theory. Bull. Amer. Meteor. Soc., 78, 1097-1106.
Roy Spencer recently wrote for TCS about Osama Bin Greenhouse.
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