Guest post By Ben Herman and Roger A. Pielke Sr.
During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere. We would like to briefly explain the arguments that have been put forth and why they are incorrect. Two of the primary arguments that have been used are
- By virtue of the second law of Thermodynamics, heat cannot be transferred from a colder to a warmer body, and
- Since solar energy is the basic source of all energy on Earth, if we do not change the amount of solar energy absorbed, we cannot change the effective radiating temperature of the Earth.
Both of the above statements are certainly true, but as we will show, the so-called “greenhouse theory” does not violate either of these two statements. (we use quotation marks around the words “greenhouse theory” to indicate that while this terminology has been generally adopted to explain the predicted warming with the addition of absorbing gases into the atmosphere, the actual process is quite a bit different from how a greenhouse heats).
With regards to the violation of the second law, what actually happens when absorbing gases are added to the atmosphere is that the cooling is slowed down. Equilibrium with the incoming absorbed sunlight is maintained by the emission of infrared radiation to space. When absorbing gases are added to the atmosphere, more of emitted radiation from the ground is absorbed by the atmosphere. This results in increased downward radiation toward the surface, so that the rate of escape of IR radiation to space is decreased, i.e., the rate of infrared cooling is decreased. This results in warming of the lower atmosphere and thus the second law is not violated. Thus, the warming is a result of decreased cooling rates.
Going to the second statement above, it is true that in equilibrium, if the amount of solar energy absorbed is not changed, then the amount of IR energy escaping out of the top of the atmosphere also cannot change. Therefore the effective radiating temperature of the atmosphere cannot change. But, the effective radiating temperature of the atmosphere is different from the vertical profile of temperature in the atmosphere. The effective radiating temperature is that T that will give the proper value of upward IR radiation at the top of the atmosphere such that it equals the solar radiation absorbed by the Earth-atmosphere system.
In other words, it is the temperature such that 4 pi x Sigma T4 equals pi Re2 Fso, where Re is the Earth’s radius, and Fso is the solar constant. Now, when we add more CO2, the absorption per unit distance increases, and this warms the atmosphere. But the increased absorption also means that less radiation from lower, warmer levels of the atmosphere can escape to space. Thus, more of the escaping IR radiation originates from higher, cooler levels of the atmosphere. Thus, the same effective radiating temperature can exist, but the atmospheric column has warmed.
These arguments, of course, do not take into account feedbacks which will kick in as soon as a warming (or cooling) begins.
The bottom line here is that when you add IR absorbing gases to the atmosphere, you slow down the loss of energy from the ground and the ground must warm up. The rest of the processes, including convection, conduction, feedbacks, etc. are too complicated to discuss here and are not completely understood anyway. But the radiational forcing due to the addition of greenhouse gases must result in a warming contribution to the atmosphere. By itself, this will not result in a change of the effective radiation temperature of the atmosphere, but it will result in changes in the vertical profile of temperature.
The so-called “greenhouse effect” is real. The question is how much will this effect be, and this is not a simple question. There are also questions being raised as to the very sign of some of the larger feedbacks to add to the confusion. Our purpose here was to merely point out that the addition of absorbing gases into the atmosphere must result in warming, contrary to some research currently circulating that says to the contrary.
For those that might still question this conclusion, consider taking away the atmosphere from the Earth, but change nothing else, i.e., keep the solar albedo the same (the lack of clouds would of course change this), and calculate the equilibrium temperature of the Earth’s surface. If you’ve done your arithmetic correctly, you should have come up with something like 255 K. But with the atmosphere, it is about 288 K, 33 degrees warmer. This is the greenhouse effect of the atmosphere.
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DirkH says:
July 23, 2010 at 9:50 am
[–snip–] It is just that we mere mortals often have a hard time following the physicists because they tend to make rather large steps in their arguments. It’s not a contradiction at all.
Yeah, large steps over the precipice …
Lemming much?
Darren Parker says:
July 23, 2010 at 10:59 pm
“The C02 loses it’s heat much faster than the humid standard atmosphere.”
What point is this supposed to make?
Phil. says:
July 23, 2010 at 12:42 pm
[–snip–]This is a common fallacy, radiation from cold to hot takes place all the time and is not a violation of the 2nd Law. Your interpretation would have the night side of the earth radiating into outer space but when it’s at noon it would stop radiating back towards the Sun! No net heat can be transferred from the cold body to a hot via radiation but the radiation is always going both ways.
Suppose you have an isolated black ball which you heat so that it eventually equilibrates at a certain temperature, introduce another ball nearby at a lower temperature, the hotter one will get hotter (as will the cooler).
Phil,
You’re either a comedian paid to post inanity, or you’re just plain inane.
If the Sun radiates to the Earth, and the Earth begins to heat, the heat energy will re-radiate from the Earth and into space.
This is so because space is cooler than either the Sun or the Earth.
If the only two objects in the universe were the Sun and the Earth, and space didn’t exist, then please DO TELL how the cooler Earth is going to transfer heat back to a very much hotter Sun.
You’ll get back on that, won’t you?
tallbloke says:
July 23, 2010 at 2:50 pm
Scott Basinger says:
July 23, 2010 at 2:31 pm (Edit)
The “greenhouse gases” heat the earth’s surface up approximately 35°C higher than it would be otherwise.”
No they don’t. They slow the rate of cooling.
Please don’t try to say that ‘this is the same thing’.
Reciprocity finds you incorrect in your assertion.
Are you willing to say that CO2 retains heat, and if so, how?
If a gas transmits energy, then it must do so always, regardless from whence the energy arrives.
Ergo, gasses cannot be said to favor either retention or shedding of energy, as the principle of reciprocity forbids it.
John Phillips:
Nope. The Second Law disallows it in every possible way for closed systems.
899, this thread was getting a boring, thanks for bringing back the farce.
Darren Parker says:
July 23, 2010 at 10:59 pm
A poster on Treehugger forums totally destroyed AGW with a simple experiment. Take Two Kilner Jars. Fill one with pure C02 and the other with reasonably humid but otherwise standard atmosphere. Heat both from the same heat source and then turn off the heat source after a while. Then measure the rate of heat loss within the Jars. The C02 loses it’s heat much faster than the humid standard atmosphere.
REPLY: We don’t live in a pure CO2 atmosphere, so the comparison isn’t valid – Anthony
—————————————————————————————————————————
Well, Anthony, we don’t live in a pure whatever atmosphere.
But the point was well made: CO2 doesn’t contribute to atmospheric heat.
So why so dismissive?
899, if you place a cup of hot coffee in a warm oven (say at 80C), and another identical cup on the kitchen bench, both will cool, but unless you have a very hot kitchen the cup on the bench will cool more quickly than the cup in the oven, this is because while both cups are emitting the same amount of IR radiation to their surrounds, the cup in the oven is receiving more radiation back from its surrounds.
Theo Goodwin says:
July 23, 2010 at 2:54 pm
Ryan writes:
“What AGW proponents are saying is that we have, in CO2, a translucent panel above our heads (i.e. it absorbs light). According to AGW proponents, if we put more and more translucent panels above our heads the area beneath the translucent panels will get brighter and brighter.”
Will a a translucent panel above our heads make it brighter?
What distinguish a Professor from the student, is that the Professor should be better at knowing when different laws of Physics can/should be applied. The student will often fail at this, but via training learn “how to think”.
It is easy to be fooled.
In this case I think Ryan is the one with the clear head? Why ?
Because it occurs to me that “a translucent panel” would act as a perpeteum mobile if it became brighter. But this is just my “instinct” saying so, there could be some tiny thing I am forgetting.
I still have great problems with that “Back-radiation”, as you all understand.
But I am no Professor. I am only one of the students. Well, ex student by now.
Bob Tisdale says:
July 23, 2010 at 6:02 pm
tallbloke: In running through the above comments, only a dozen or so even think to mention the oceans. Kind of odd, don’t ya think? But a few noted that the temperature of the earth would be much cooler if not for the oceans.
The oceans, of course, have their own “greenhouse effect”; that is, downward shortwave radiation can warm the oceans as deep as 100 meters but the oceans can only release heat at the surface. So all in all, most of the arguments miss the obvious.
In trying to fight alarmism and debate with warmism over the years I notice they always want to talk about the atmosphere, never about the oceans.
Back radiation can’t heat the oceans.
Therefore, the increase in ocean heat-energy content since the fifties is solar in origin.
The amount of energy increase in the oceans since at least the fifties (since the mid thirties according to my model) is greater than restriction of cooling by additional GHG’s can account for.
Therefore, solar energy is accumulated in the oceans on multi-decadal timescales when the amount of insolation at the surface is in excess of the long term average, which coincides with the level at which the oceans neither gain nor lose heat (equivalent to ~40SSN).
Therefore we need to consider the cumulative total of solar energy input not just it’s instantanous level.
Since the increase in ocean heat-energy content necessarily inceases the sea surface temperature, which increases the atmospheric temperature ~2-3 months later. http://www.woodfortrees.org/plot/uah/from:2007/plot/hadsst2gl/from:2007/scale:1.7/offset:-0.3
There’s your global warming.
I have integrated sunspot area as a running cumulative total of departures from the ocean equilibrium value as a proxy for retained heat of insolation (ocean heat content anomaly) and graphed it against SST back to 1880. I also mention on the graph where the epochs of positive and negative PDO are (noted as periods of El Nino and La Nina dominance). The fit is good all the way allowing for PDO oscillations. The co2 warmista never show you a graph going back prior to 1900 because their rough correlation breaks down beyond that.
Over 2000 visitors have looked at this graph in the last few days, and most have left positive comments. There has been one unsubstantiated rejection, and two whinges about Y axis issues. It’s true that it’s difficult to quantify at historical distance, and with uncertainty about cloud level amplification of the solar input, but a good fit is a good fit.
http://tallbloke.wordpress.com/2010/07/21/nailing-the-solar-activity-global-temperature-divergence-lie/
By the way:
Ninderthana says:
July 23, 2010 at 7:58 pm
Brilliant post.
So even contrarian scientists agree: “Yes, Virginia, there is a Greenhouse Effect”!
Dr. Roy Spencer also has a go at this on this blog:
http://www.drroyspencer.com/2010/07/yes-virginia-cooler-objects-can-make-warmer-objects-even-warmer-still/
The differences in the science seem to boil down to climate sensitivity to CO2 increase.
Could Herman and Pielke propose a joint study to determine this once and for all – the experiment or experiment(s) to be funded by the energy industry and/ or a collection of governments.
Barry Moore says
July 23, 2010 at 9:11 pm
Outgoing radiation is largely invisible to greenhiouse gases as it radiates at too low a wavelength to be captured. C02 only captures heat at -30C, such that is found at the poles – and again, its onl the 1st 100ppm that does this, after which its saturation window closes, something like a tissue dropped in a bath will lose its ability to absorb more water when its saturation window closes. Doubling the tissues to 0.05% (or 500ppm) won’t absorb and more water in a full bath than 0.04% will. Secondly. Assuming the earth heats to an average 15C, from the sun – this average includes everything from deserts at 45C to the poles at -50C. There is no physical mechanism by which outgoing radiation an increase it to 16C. It is the same radiative principle by which heating a liquid to a constant 60C (1st power radiation from a heat source) will not go beyond 60C by the radiation the exits from the liquid (2nd power) *bouncing* back to the liquid (4th power). In fact, optimum temperatures are achieved through solar effects, so reduced energy (radiation)leaving earth on the basis of that 1st power will increase the temperature. If theere were an ideal greenhouse, it would keep it at 15C day and night. Thats not the same as an increase
However, what concerns radiative physics is the heat absorbtion of c02 in the atmosphere. It absorbs radiation at 13.7-16.3 microns with a peak of 15 microns – yet radiation on average leaves earth at 10 microns, which equates with 15C, or 288K. 15 microns equates with subzero temperatures that can be found at the poles – so heat capture of c02 in the atmosphere is a rather rare event, and is fixed at around 4-6% of atmospheric thermal energy, achieved by the 1st 100ppm where its absorbtion window closes – well outside of normal temperatures. Its true that a c02 molecule’s stretching mode would allow it to transfer energy to other atmospheric molecules, such as the ghg water vapour, but this requires so much energy that it doesn’t occur even at 300K, with the c02 absorbtion bands, and there’s some 3,000 other molecules apart from c02 in a given volume of air, making collisions between thermally excited c02 molecules very unlikely. Molecules of like kind are more efficient at transferring energy to one another. In the absence of such, thermal degradation takes place very quickly. (a billionth of a second), so vibrationally excited c02 thermalises very quickly with oxygen and nitrogen
Dave Wendt says:
July 23, 2010 at 1:36 pm
Many years ago Sapir and Whorf posited a theory, a much oversimplified statement of which would be, that language dominates thought. It never got a lot of traction in the linguistics community, though occasional efforts are still made to support versions of it. The way the climate debate has developed and proceeded suggests that maybe their work should be given more consideration. The rather simple error of selecting a seriously flawed analogy, the greenhouse, has lead to decades of people talking past each other on this topic, mostly it would seem, because they are trying to rectify their arguments to an analogy that has no common definition and fundamentally misstates what is actually occurring.
If a person is interested enough to argue about the greenhouse effect, he ought to be interested enough to have learned that the analogy is flawed. The trouble is not language. The trouble is that some people are egoistical fools.
Andrew W says:
July 23, 2010 at 2:20 pm
Thank you Ben Herman and Roger A. Pielke Sr for the tidy post, it’s resulted in the funniest thread I’ve read in ages, that kill-joy from Brenchley tried to derail it all but to no avail. The thread is a testament to humans being rationalising rather than rational creatures.
I don’t think the problem is rationalization. I think it’s egoism, and I would almost say, solipsism.
Jeff @ur momisugly 8.20.
Thats the most sensible thing I’ve read in ages. Thanks.
My understanding is the effect of additional CO2 on outgoing radiant energy is logarithmic. This has not been included in the excellent description in the article which suggests more CO2 causes directly proportionately more warming.
Bob Kutz July 23, 2010 at 8:35 am says:
“Can you tell me, does atmospheric CO2 currently absorb 100% of the longwave IR in the bandwidths which apply? If so, at what altitude is the saturation achieved?”
Well it should be simple enough to measure the altitude where saturation is achieved.
Why don’t scientists do that instead of what they are wasting time and our money on?
I see that NIWA in NZ have just wasted $12 million on a new computer for climate modelling.
“Assuming that additional CO2 would lower that altitude”
Surely additional CO2 would raise the altitude where saturation is achieved.
Jeff says:
July 23, 2010 at 8:20 am
“slowing down the cooling of an object cannot cause it temperature to rise … THAT would violate the 2nd law …
if a black box is warmed to x degrees by the sun then its temperature cannot rise above x no matter how much greenhouse gas it is surrounded by …”
Nonsense, to lift its temperature all you have to do is put the black box in a container that still allows it to continue to absorb full sunlight but that restricts the escape of heat, or surround it with GH gases which would do the same thing.
To those who think that CO2 has no effect on eath’s energy budget, this emission spectrum graph is from a post by Steve McIntyre on ClimateAudit (See http://climateaudit.org/2008/01/08/sir-john-houghton-on-the-enhanced-greenhouse-effect/ ).
http://climateaudit.files.wordpress.com/2008/01/daly_spectra.gif
Steve writes “The large notch or “funnel” in the spectrum is due to “high cold” emissions from tropopause CO2 in the main CO2 band. CO2 emissions (from the perspective of someone in space) are the coldest. (Sometimes you hear people say that there’s just a “little bit” of CO2 and therefore it can’t make any difference: but, obviously, there’s enough CO2 for it to be very prominent in these highly relevant spectra, so this particular argument is a total non-starter as far as I’m concerned. )”
Note that the ‘effective emitting altitude’ is around 6000m which is the average height that the incoming solar energy is balanced by the outgoing IR energy. Increasing CO2 will increase the height of the ‘effective emitting altitude’ which, because of the lapse rate, means that the lower atmosphere and surface will warm.
The main concern (for me) is that I’m becoming increasingly persuaded by the positive feedback argument. It seems logical that if you remove CO2 from the atmosphere the amount of water vapour will reduce. I can’t think of any reason why the dsme process shouldn’t happen in reverse. The onus, therefore, is on leading sceptics such as Lindzen and Spencer to settle the feedback part of the issue.
The moon has no atmosphere, an albedo of 0.12, and an average temperature of -23c as measured by experiments left on the moon by two of the Apollo missions.
The earth has an average albedo of .30 so, without greenhouse warming, should have an average temperature colder than the moon.
Greenhouse warming is real but it’s water, in all its phases, that runs the show, not C02.
just to be clear the average temperature of the moon is MINUS 23c
John Finn:
But the feedbacks are crucial, right from the outset.
If the surface is 1.2 deg warmer then it must be emitting 4W/m2 more (I have it at 3.6W/m2, but we won’t quibble)
But a warmer surface will also mean more convection and evaporation.
So, if the surface is receiving 4W/m2 more, and it’s emitting 4W/m2 more, then where does the extra energy come from for the increased convection and evaporation?
The answer is, the surface cannot warm by 1.2 deg, otherwise it would be losing more energy than it’s getting.
That’s a negative feedback which has to be taken into account right from the outset.
I still have a question (which I have asked before, but don’t think was clearly answered).
While CO2 blocks radiation from escaping from the atmosphere, thereby producing a positive feedback, to what degree does CO2 block radiation from entering the atmosphere, thereby producing a negative feedback? Has that negative impact (if it exists) been included in the calculations?
Clouds can have a positive feedback effect by keeping heat near the ground from escaping more quickly into the upper atmosphere, but the clouds also can create a negative feedback by keeping heat from reaching the ground in the first place by reflecting the radiation back into space. My understanding is that under some circumstances the net effect of the clouds can be negative. To what degree is CO2 like that?
“Can you tell me, does atmospheric CO2 currently absorb 100% of the longwave IR in the bandwidths which apply?
If so, at what altitude is the saturation achieved?”
Logic would dictate that *if* 100% of the longwave IR is already being absorbed in the bandwidths CO2 does its absorbing, than increasing concentration can not absorb anymore because there is no more IR left in that bandwidth to absorb!
Unless there is an increase in radiation from either reduced cloud cover or increased TSI….
Arno Arrak says:
July 23, 2010 at 9:51 am
Trouble with carbon dioxide greenhouse effect is that it requires carbon dioxide to absorb infrared radiation and thereby get warm. This simply does not happen because the infrared band of the atmosphere is saturated and no further additions of carbon dioxide to air can change the already-existing greenhouse effect. This follows from the empirical observation based on NOAA’s weather balloon database that the global average annual infrared optical thickness of the atmosphere has been unchanged for 61 years, with a value of 1.87. This means that constant addition of carbon dioxide to the atmosphere for the last 61 years has not had any influence on the transparency of the atmosphere in the infrared or the optical thickness would have increased. And it didn’t. See Ferenc Miskolczi E&E 21(4):243-262 (2010). His is the first determination of the actual optical thickness of the atmosphere in the IR despite the billions spent on “climate research” by “climatologists” who spew out thousands of “peer reviewed” papers every year.
___________________________________
If what Arno Arrak says is true, then there is no point discussing all this. No need to spend billions in research to save the planet while the IPCC can disband or else diversify into designing raiways (they already have an expert railway engineer) or the production of soft porn (same engineer doubles up as porn writer when he is not watching melting glaciers or navel-gazing).
In fact, there are a hundred scientific reasons why CO2 gas should be considered as an irrelevant parameter in the climate forcing budget, while the only parameter that causes climate change is ‘chaos’ as we have now learnt after so many years of climate research, failed predictions and goal-post moving by the warmists. When are our politicians and their scientific cabal going to accept reality?
What a fantastic thread, so learned and civil unlike the shrill hysteria, interspersed with ‘comment removed’, you get at some sites.
Please keep posting, all you learned people.