Explaining misconceptions on "The Greenhouse Effect"

Guest post By Ben Herman and Roger A. Pielke Sr.

Image: University of Arizona

During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere.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

  1. By virtue of the second law of  Thermodynamics, heat cannot be transferred from a colder to a warmer body, and
  2. 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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Vince Causey

Good article Dr. Pielke. It is unfortunate that this needs saying at all, but I fear the infamous G&T paper has done a bit of damage to the credibility of sceptical science.


Greenhouse Gases emitted in all directions. Also into outer space. Seems to forget this detail.

Laws of Nature

Hi there,
well .. I usually describe it the following way:
It is a fact, that with increasing CO2 the characteristic CO2 emission into space comes from a greater atmosphere layer (measured by the temperature of the emitting molecule via the spectrum width).
In layman terms this means the lower layer losses one way to transport energy and thus has a lower thermal conductivity (which means it warms)
This effect is well understood and can be calculated to the 3.7 W/m^2 cited by IPCC, the question reamins, what this means to the temperature.
All the best regards,

The amount of warming from the greenhouse effect varies by a large amount between the tropics and the poles, due to the amount of water vapour in the atmosphere. The tropics experience much more more greenhouse effect than the south pole, because there is almost no water vapour in the atmosphere over the south pole.


My guess is all of the feedback ‘constants’ are driven by the variables “The rest of the processes, including convection, conduction, feedbacks, etc. are too complicated to discuss here and are not completely understood anyway.” Without understanding those variables ones instrumentation is left to quantify the dynamics. Empirical prediction?

andy adkins

The conditions forcing the escape of radiation the atmosphere must also force the escape of atmospheric gases. As such, wouldn’t the conditions for escape of those gases be the determinant of the rate of the greenhouse effect
….There is dusted together water on the moon and mars………




Surely the ultimate question is – Is the Earth sensitive to changes in CO2 levels?
The earth has had much higher levels of CO2 in the past so the knee jerk reaction to this must be NO, or else we would not be here to talk about it.
Is industrialisation altering our atmosphere to such an extent that we face imminent virtually immediate doom?
Again looking at the last 20 years I would say NO. So whatever we need to do whatever we need to measure and calculate we can do rationally and sensibly and slowly and openly.
Is this happening? NO ….

Leonard Weinstein

You have to add the trapping effect of the clouds and you have the basic story complete.


Anyway, it looks like Kevin Trenberth’s backradiation hop (up, down, up, down) as described here
vastly overestimates back radiation because they just didn’t follow the established vector calculus rules (subtracting energy that goes into the opposite direction).
The atmosphere is due to the density of CO2 a dense fog for the absorption bands of CO2 even where there is no water vapor, and this was so even before the increase in CO2 emissions. The light (or LWIR) from a diffuse surface like the Earth’s surface must be diffuse. The fog will re-emit the light into all directions equally. What does it matter whether a ray from the surface is intercepted after 23 m on the average or after 15 m the first time, to be re-emitted? Nothing at all when the atmosphere is 10,000 times as high.


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 …
x becomes the upper threshhold of the objects temperature (assuming no other energy inputs …)
yes, it may REMAIN at some temperature between x and zero longer than it would but it can never rise above x … it may be relatively warmer because of slowed cooling but it has certainly not “warmed” up …
if you say something has warmed you are implying that its temperature has RISEN … not cooled slower …

J. Bob

Good article. In a way it reminded me of another item I read today, not exactly on the subject, but interesting, about Enrico Fermi, and connections.
This connection is CO2 causing GW simply because CO2 was increasing and some recent warming. This idea was noted in similar to a train of thought that Enrico Fermi discussed with his friends Teller, John von Neumann, and others over lunch at Los Alamos. The subject was the recent disappearance of NY trashcans and increased appearance of flying saucers. The logical, but not necessarily correct, conclusion was aliens were stealing NY trashcans.

“The rest of the processes, including convection, conduction, feedbacks, etc…. are not completely understood anyway. … There are also questions being raised as to the very sign of some of the larger feedbacks to add to the confusion. ”
Dr Pielke, I note you talked about warming the ground, but carefully avoided reference to the ocean, the really big dog on the climate block. Since longwave radiation can’t penetrate the ocean, but only causes increased evaporation at its surface, and since as you note, there’s lots we don’t know about convection etc, what makes you so sure adding more co2 will cause warming? Is Miscolzci to be ignored forever?
Earth warmed while solar activity was high, and cloud albedo diminished, and ocean heat-energy content has been dropping since 2003 when the sunspot count dropped below its long term average of 40, and cloud increased again.

I guess I have a problem with the over simplistic model. Yes, absorbing gasses in the atmosphere ‘slow’ the cooling because the radiated heat bounces a like a pinball from molecule to molecule before it actually radiates to space.
However, the movement of air columns can shorten or lengthen that wayward path, as can precipitation which tends to absorb heat and drop it back into the oceans.
When air heats it rises, but the atmosphere also expands (something easily detected in satellite orbits, which experience changes in atmospheric drag constantly as the atmosphere expands and contracts – sometimes regionally). An expanding atmosphere lowers the density as volume increases. Already ‘thin’ air becomes even thinner, which means the chances of IR radiation bouncing back into the atmosphere should decrease and radiation rates escaping should increase.
If the Earth’s atmosphere actually has built in thermal balancing – which must be the case given it has survived for billions of years – then the combination of precipitative cooling and increased radiative cooling because of lower density and greater surface area to space would seem to more robust than many climate alarmists would consider.
This becomes even more true if recent human actions on climate are driven by the UHI and expanding population centers (changing the basic reflective/absorptive characteristics of the Earth’s surface). I seriously doubt CO2 or any GHG can go into a ‘runaway’ mode. If you look at Mars, Earth & Venus it is not the GHG gas necessarily that drives their climate, but the distance from the Sun (i.e., solar flux intensity) and their mass (how much atmosphere they can hold gravitationally) which dictated their atmospheric stability point.
No one has proved reducing GHG on Venus or increasing it on Mars would change a damn thing. These kinds of theories border on the science fiction concept of terra forming – something never proved even slightly.
The billion year stability of our atmosphere, through massive eruptions, massive (but slow) changes in content, though large impact events, would indicate the cross-checking balancing mechanism always bring the system back to a nominal range of climate. A range we have seen for millions of years and a wide range of CO2 and GHG concentrations.


While it doesn’t refute your argument, I want to point out that assertion #2, technically, is not correct. There are many sources of energy on Earth that are not sun related. Simply because it has mass, the Earth contains ~5^41 J of energy. It creates a vast gravitational well that imparts energy on all objects on the planet. Additionally, a lot of our energy sources have no ties to solar energy (e.g. fission reacts on Uranium which is, most likely, a remnant of a distant supernova).
However, if you were to say that the sun is the source of all BIOLOGICAL energy, I wouldn’t argue.

“The rest of the processes, including convection, conduction, feedbacks, etc. are too complicated to discuss here and are not completely understood anyway.”
But that’s the crux of the matter. For starters, there cannot be a proper greenhouse effect in the presence of constant convection. And the biosphere is a temperature regulating mechanism that constantly changes the chemical composition of atmosphere, therefore defining, where the equilibrium will be.
Therefore, all this talk about “greenhouse effect being real” is nonsense. No, it’s not “real,” it exists only within the simplistic framework of intentional misunderstanding.

Dr David

How much of the 33 degrees is due to heat escaping from the Earth’s core and tidal forces?

anna v

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.
A bit misleading, this last paragraph.
The dry atmosphere consists of:
N2 78.084%
O2 20.946%
Ar 0.934%
rest 0.03768%
and if there is humidity around, H2O 0.4% and more near the surface.
The trouble is not with whether the atmosphere keeps temperatures temperate, but whether the tiny amount of CO2 can contribute significantly to this, considering also that H2O covers most of the spectrum and CO2 only some windows.
I am curious if anybody has calculated a toy earth with only N2 and O2 as an atmosphere. Deserts do get cold at night and hot in the day, but on average would not be too far off current global averages.

I question the analysis by Herman and Pielke in
Comments from Herman and Pielke are particularly wellcome.


“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.”
Um, what about an atmosphere devoid of greenhouse gases? What about the dry adiabatic lapse rate?

Bob Kutz

That is a very good simple explanation of the greenhouse effect.
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?
Assuming that additional CO2 would lower that altitude, what sort of effect would this actually have on surface T? I mean, given what we know about the atmosphere I would think convection would distribute this additional atmospheric heat well enough to prevent a significant increase to the ground temp and probably keep the increased surface atmospheric temp from increasing a great deal as well. I guess what I’m really asking is, if all of the IR that CO2 can absorb is already being absorbed by CO2 within the first several tens of meters above the surface (to my understanding), what additional impact can more CO2 have on the overall heat content of the atmosphere, and does it really make a difference if that heat is added in the first 50 meters or the first 5?
Maybe this isn’t so, I do not know for a fact if the CO2 is currently absorbing 100% of the IR it is capable of, though I’ve read and been told that this is true. Maybe science doesn’t yet know the answer to these other questions, which would seem plausible as this is almost bordering on chaos theory; (everything’s just so, you have all of the measurements and can accurately predict what will happen forever, then a butterfly flaps it’s wings and all of your calculations go awry.)
Or maybe I’m just way off base in my line of thinking here.
Please let me know your thoughts.
And again, this is a really good article in describing the greenhouse theory of global warming to someone (like me) who hasn’t the scientific background to do the math, but is really trying to understand and keep up with the debate.

Dr. Pielke
For your demonstration of the greenhouse effect WUWT has used the Arctic part of the globe, which is currently very popular with many researchers. In a way of a modest contribution, I think I may have found an important correlation as shown here.
You may not agree with the explanation for this unusual phenomenon, but in the interest of science and the readers of WUWT (well over 3000) who viewed this graph, I would very much appreciate your comment.
Thank you.

Pamela Gray

This is entirely reasonable. For me, that we have greenhouse affects on the planet is rather boring (not that your presentation was). It’s kind of a stable thing and of not much complexity relatively speaking.
It’s the feedbacks and turbulent nature of the thermosphere that fascinates me. Much harder to simply explain and therefore endlessly fascinating to me. If each of our gasses and particulates in our overturning thermosphere (warm to cold in height so it wants to be turbulent) were colored, it would be a right pretty ever changing kaleidoscope of swirling color topped with a ribbon-like fairly stable stratospheric layer (cold to warm in height so those layers don’t want to be turbulent), and so on. If one were to try to demonstrate AGW increases in any one color in that thermosphere, stratosphere, etc, you would be hard pressed to do so. But regardless I could stare at such a presentation for hours.


DirkH says:
July 23, 2010 at 8:20 am
“[…]The atmosphere is due to the density of CO2 a dense fog for the absorption bands […]”
Such a re-emitting fog must tend towards an equilibirum, and that’s why its exact density does little to change the overall distribution of re-emittance towards the ground or space; just like adding another 15m of atmosphere does not change the distribution. I’m assuming a 100% re-emittance here. If the re-emittance is smaller, energy will just be distributed to non-LWIR-emitting molecules like O2 which results in heating where we enter the area of “not well understood anyway” convection and conduction so that would steal some more energy from Kevin Trenberth’s beloved backradiation, torpedoing his assumptions further.

Leonard Weinstein

I don’t think that most of the arguments circulating (such as Lubos’s or mine) are contradicting what you said. Their point is that, at least for Venus, it is mainly the fact that the atmosphere is very tall due to much higher mass of the atmosphere that causes the very high surface temperature. There still needs to be greenhouse gas and clouds, but they could be a far lower percent of the composition and still get most of that high temperature as long as the mass of the atmosphere is high enough to maintain the approximate altitude where outgoing radiation leaves the atmosphere. If the Earth had 100,000 ppm CO2 rather than 390 ppm, the temperature would only be a few degrees higher that at present, due to the limited size of our atmosphere. In other words, it is the COMBINATION of mass of the atmosphere that is resulting in it’s thickness combined with the trapping effect of greenhouse gases and clouds that result in the ground temperature. The concept that had been often stated, of a “runaway” greenhouse effect, is what brought that point up. There is no runaway, just straightforward fluid dynamics and radiation heat transfer.


bah. I pounced on the sentence without reading the context. You were quoting other sources. Nevermind. I guess I’m the troll here. 🙂

Mike Davis

This shows a lack of understanding of how a green house works. A green house restricts transfer of energy it does not heat or cool. By claiming that green house gasses that restrict energy transfer result in warming you are missing half the equation because they also restrict the increase in warming to start with. The restriction leads to less extreme temperatures both warm and cold. If the globe was experiencing an increase in Green House Effect we would see a reduction of extreme weather events because of the restrictive nature you claim. There is no evidence of that! Climate continues within the range expected for an interglacial period as displayed by historic interglacials.

John A

Dear Dr Pielke:

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.

What are “IR absorbing gases”? As far as I am aware, gas molecules can absorb light quanta but by becoming excited, they give up the energy just as quickly. There is a slight loss of energy because of increased entropy on the release of that energy, because some of that motion is converted into molecular oscillation and some into translational energy.
You appear to reject the nomeclature of “greenhouse theory” because that isn’t how greenhouses warm up, but you describe the warming of the lower atmosphere as if there was a sheet of glass high up there which heats up and then magically re-radiates the energy to the ground and then slows down the re-emission of the heat back into space. This is a false model.
Real greenhouses don’t work like this either – they warm because they restrict the convectional motion of the air, something demonstrated one hundred years ago by Robert Wood.
The atmosphere also has massive convectional motion driven by the Sun which (somewhat to my surprise) is completely ignored in those idiot cartoons by Trenberth which treats the Earth’s atmosphere as if it was made of lucite. The circulation of the oceans is an even bigger thermodynamic engine driven by the Sun.
I’m afraid you have failed to grasp the main criticism of the greenhouse gas hypothesis – the atmosphere is not restrained from convecting.
Why does it not get so cold at night? Because of water vapour in the atmosphere. Not because water vapour is “a powerful greenhouse gas” whatever that means, but because in the atmosphere water vapour changes state from gas to liquid as it cools and liquid to gas as it heats up. Thus some of the energy from the sun is captured in the latent heat of vaporization (NOT “re-radiated”) of water backwards and forwards from gas to liquid to gas. The heat captured by water condensing in the atmosphere during the day is transported to the nightside (by the rotation of the earth) where the loss of the Sun is compensated by emission of heat as water evaporates and re-emission of heat as water condenses higher up.
It is the water vapour effect of retaining heat by constant cycling from liquid to gas to liquid that slows the re-emission of heat energy back into space, not “re-radiation”. Water vapour clouds glow in IR because of this effect, which is why they can be pictured at night from satellites.
The more water vapour in the atmosphere (as in the tropics) the greater this heat trapping in clouds becomes.
It explains why the greatest difference between day and night temperatures occurs in the major deserts where water vapour in the atmosphere is scarce. It also explains why the difference between day and night on Mars is even more extreme than the Earth despite having eight times the partial pressure of CO2 at the surface than the Earth – its the lack of heat energy “trapped” by water vapour of which Mars has very little, from changing state in the atmosphere in the form of clouds.

Richard Garnache

While I agree that so-called greenhouse gases reduce the cooling rate of the earth, the degree that CO2 affects that cooling rate is in question. Ibelieve the formula used by IPCC is in serious error.
The IPCC contends that doubling the co2 concentration will cause a forcing of 3 to 6 degrees C. Unfortunately they seem to be better at fudging data than applying physics. Their standard calculation is shown below.
∆T=4.7ln(c/co)=4.7ln(836/368)=4.7*.69=3.2Deg C
However, H20 also absorbs 15 micron radiation. Since water vapor concentration is 1 to 4% of the near earth atmosphere, it would be more accurate to include all gasses that absorb 15 micron radiation. To be clear, c should include 10000ppm water vapor plus 836 ppm co2, and co should be 10000 ppm water vapor plus 386 ppm co2.
∆T=4.7*ln(10836/10386) = 4.7*.044 = .2 degrees C
I can live with that.

Leonard Weinstein

I need to add another point mainly related to Venus. Absorption of the radiation from the ground is important so that back radiation nearly equals radiation up as a trapping mechanism. However, this DOES NOT significantly directly change the atmospheric temperature. The main factors that determine the atmospheric temperature are the effective location of outgoing radiation (which sets the value of temperature in the atmosphere at that location) and lapse rate, and the lapse rate will (on the average) be the wet or dry lapse rate. The atmospheric convection totally dominates in retaining that lapse rate level (it transports much more energy that the radiation flux). The trapped heat was important is setting the location of the outgoing radiation, and for Venus, that is its only important function. Earth is much more complicated due to the fact that the outgoing radiation leaves from all altitudes from the ground up, so that can’t be treated as simply as Venus.


The radiation density in my idealized CO2 fog must, when it reaches equilibrium with the LWIR-radiating Earth surface, have the same radiation density as the Earth’s surface. It cannot exceed this radiation density. The CO2 concentration is not a variable that can manipulate this. The fog model only breaks down with extremely low CO2 concentrations; but the variation in CO2 concentration from 270 ppm to 390 ppm does absolutely NOTHING to the radiation density in this fog.


tallbloke, the GHE will by itself (i.e. without feedbacks) cause warming. However as it happens, other collateral effects may cause the warming to be increased, decreased or perhaps even reverted into cooling. Roger is only talking about the GHE, alone, without considering feedbacks.


So any measured INCREASE in downwelling CO2-caused LWIR radiation must be caused exactly because this fog model is idealized and the real atmosphere behaves differently. IOW, CO2 moelcules collide with O2 etc and heat the gas mix up via conduction. Where, again, energy leaves the radiation model and turns into plain old kinetic energy, heats the atmosphere up, leading to convection. As Abdusamatov has said “Heat rises up, not down”.


Tallbloke is right. Do you prepare your breakfast with a hair dryer? “Your are going against the wind”. Have you already found that atmosphere’s heat piggy bank you dreamed of?. You integrate from 0 to infinite, that’s like asking, how much will I warm up by putting on my bed an infinite number of covers?. Add all the warm you can to the atmosphere and it won’t warm up sea water. Please, let us not cheat people: The heat capacity of the air is 3227 times less than water. Would you warm your feet, when cold, with a bottle filled with hot air, or instead with hot water?

“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.”
I politely disagree. That 255K has been obtained by blackbody calculation, but confusingly with present Earth’s albedo (which is predominantly made by clouds and snow/ice). Look at the nearby Moon with albedo 0.11 (Earth has ~0.3): its average temperature is 270K.
So for start, 288-270K = 18K is more correct.
Second, this temperature difference is because of existence of ATMOSPHERE, not greenhouse gases. It is easy to show, that on Earth, the main “greenhouse gas”, water vapor in various states, effectively cools the Earth: a) by clouds, creating major part of albedo, b) by evaporative cooling, preventing all Earth being hot as dry deserts, c) by ice/snow, participating on albedo.
Mere greenhouse gases in a thin atmosphere create no “greenhouse” effect. Mars atmosphere consists of 95% CO2 – but Mars blackbody T = Mars actual T = 210K.
You need a bulk atmosphere (in our case composed of N2 and O2) and water in liquid/vapor state to get habitable conditions with mild diurnal cycle and pleasant average temperature. Our nights are warmer than on the Moon not because of “backradiation”, but mainly because the atmosphere holds the daily heat. “Backradiation” on Mars does NOTHING, and the effective concentration of CO2 there (6,000 ppm) is that of CO2+water vapor on Earth (if water vapor creates 90% of GHE).
In my chemist opinion, the greenhouse theory confuses the simple heat storage in the atmospheric mass with hypothetical arrows in radiation diagrams.
Not to forget, how do I know the IR radiation is coming from IR active gas, and not from nitrogen/oxygen bulk atmosphere? That forgotten 99% of the atmosphere radiates in IR spectrum, as every material with its temperature above zero K.


Could you tell me how much IR-radiation is coming straight from the sun to the earth?

Ralph Dwyer

Speaking for the simple-minded among us, I think we are very fortunate to have an atmosphere that “behaves/responds” as well as it does supporting life as we know it. Keeping it simple, I don’t think anyone would argue that the atmosphere is in equilibrium. But it is “responding” to something. Right? Could it be the sun above and/or the oceans and land mass below or volcanic emissions or even the pesky humans? I’ll stick with Ian Plimer on this one and say the pesky humans are the least of out worries.


….. but the atmosphere is not a perfect blanket around this planet. Additionally CO2 only constitutes a small fraction of the atmosphere’s composition. So the % of IR radiated directly back to Earth is small.
Also the oceans, which covers 70% of this planet’s surface, lose most of its heat thru evaporation, which involves a completely different physical process.
If this planet had no oceans and a thick atmospheric blanket of CO2 then I would agree that there would be a significant rise in surface temperatures ……….. but this planet doesn’t.


What is Governing the Temperature of the Earth?
The surface of Planet Earth is heated by the incident short-wave electromagnetic radiation from the sun. In order to balance the temperature of the earth, most of this incident radiation energy is, contrary to the assumption made in the AGW hypothesis, removed from the surface by convective cooling by a flowing atmosphere and by evaporation (removal of latent heat) from the surfaces of the seas, lakes and moist soil; and by transpiration of plants. Only a small fraction of the incident energy is radiated by the surface towards space in the long-wave infra-red (IR) part of the electromagnetic spectrum [1]. Consequently, the lower atmosphere, is heated by convective heat transfer from the surface of Earth; by release of latent heat during condensation of water vapour (formation of clouds) and; to a small extent, by thermalisation of excited GHG molecules. The so heated air parcels increase in volume (reduce their density) and rise towards higher altitudes, while their temperature reduce along the lapse rate function. The rising warm air is replaced by cooler air, thus maintaining a continuous convective churning/stirring of the atmosphere that we call wind.
In the upper part of the troposphere and in the stratosphere, IR energy can more efficiently be emitted towards space to achieve the required radiation balance of Earth’s. That is, the estimated effective radiation balance temperature for the earth, ‑18°C, is established in the upper portion of troposphere and in the stratosphere and not at the surface of the earth, as anticipated by IPCC and the AGW proponents.
The bottom portion of the troposphere and thereby also the surface of the earth, exhibit an average temperature of +15°C. This is approximately 33 K higher than what can be estimated based on the radiative balance with space. This temperature increase is the direct result of the presence of an atmosphere, with its given mass, within the gravitational field of the earth (see contributions by Jelbring and Thieme below). The atmosphere (the air), with its mass, is attracted towards the surface of the earth by the gravitational field. Most of this atmospheric mass will thus reside close the surface of the earth where it is compressed to a higher pressure (on average 1.013 bar) and obtains thus a higher temperature. Correspondingly, the atmosphere becomes thinner (less compression and thus lower pressure) and cooler, the higher the altitude is. This pressure and temperature distribution is governed by a restricted thermodynamic equilibrium, so-called adiabatic condition. Such a condition prevails when the size of the air parcels is large in comparison to the length scales for heat conduction and diffusion during the time interval pertaining to the state change. Adiabatic changes in temperature thus occur due to changes in pressure of a gas while not adding or removing any heat from or to the surrounding. This entails that the total energy content in an air parcel with a given mass remains constant when it moves vertically, that is, the sum of potential and thermal energy remains constant, independent of the altitude.
The (vertical) circulation of the air is a continuous process that is driven by the sun and the dynamics of the planetary atmosphere. At high altitude (high potential energy), a parcel of air of given mass has a large volume and low temperature (low thermal energy). When brought to lower altitudes (low potential energy and high thermal energy) it becomes compressed and thus heated. Again, the temperature of the air parcel will be governed the lapse rate function, which is a consequence of the prevailing thermodynamic equilibrium under adiabatic conditions.
The mathematical description of this mechanism has been called the adiabatic model of atmospheric temperature (see papers by Khilyuk and Chilingar) and can closely (within 0.1%) describe the long-term average temperature distribution as function of altitude in the troposphere. The normal atmospheric pressure (1.013 bar) near the surface of the earth will bring the air temperature to around +15°C, or TEarth  33 K higher than the temperature determined from the radiation balance between incident (short-wave) radiation from the sun and outgoing (long-wave) radiation from the upper part of the atmosphere towards space.
The cyclic heat input from the sun (over day and night; seasonal variations at different latitudes, etc.) provides the driving forces behind the continuously circulating atmosphere and its vertical transport of heat from the surface of the earth to higher altitudes, where heat balance can be established by long-wave radiation towards space. Well proven, basic physics considerations (radiation balance and adiabatic compression) therefore directly explain the observed temperature of Earth’s atmosphere, without the need to revert to obscure and unverified greenhouse effects from greenhouse gases.
The Hothouse Venus
Planet Venus, with its CO2 rich atmosphere (96.5% CO2) has a very high surface temperature, in the order of 462°C (735 K). This high surface temperature is often claimed to be the result of a runaway greenhouse effect due to the high CO2 concentration, evaporation of the surface water and subsequent rise of the levels of other GHGs. This, of course, sounds plausible in the ears of the AGW proponents, who want to scare the inhabitants of Planet Earth that similar dramatic temperature increases (beyond the tipping point) may develop also here, if we do not take appropriate measures to curb the emission of GHGs.
There exists, however, a physically well-founded, explanation for the high surface temperature on planet Venus, namely the adiabatic model of atmospheric temperature (see papers by Khilyuk and Chilingar), mentioned above. Not only is the concentration of CO2 much higher at Venus than on Earth, but also the atmospheric pressure at the surface of Venus is much higher, approximately 90 bar. While the gravitational effects on the mass of the (dynamic) planetary atmosphere heats the bottom of the atmosphere and the surface of Earth by TEarth  33 K above the effective temperature expected from radiation balance alone, the same effect on Venus heats its surface by TVenus  507 K above its effective radiation balance temperature, which is ‑45°C (228 K). The adiabatic model of atmospheric temperature also well describes the temperature of the Venusian atmosphere as function of altitude, within 1%. Again, there is no need to revert to an (unverified) runaway greenhouse hypothesis to explain the high surface temperature of Venus. Plain, well established, physics suffices. Consequently, the (runaway) greenhouse effect does not exist.
Suggested Reading:
H.R. Jelbring. The Greenhouse Effect as a Function of Atmospheric Mass, Energy & Environment, Volume 14, Number 2 – 3, May 2003, pp. 351-356, http://ruby.fgcu.edu/courses/twimberley/EnviroPhilo/FunctionOfMass.pdf
Hans Jelbring, Politics and the Greenhouse Effect, http://www.tech-know.eu/NISubmission/pdf/Politics_and_the_Greenhouse_Effect.pdf
Heinz Thieme, The Thermodynamic Atmosphere Effect – explained stepwise, http://realplanet.eu/atmoseffect.htm
L. F. Khilyuk, G.V. Chilingar, On global forces of nature driving the Earth’s climate. Are humans involved? Environmental Geology, Volume 50, Number 6 / August, 2006, pp. 899-910, http://www.springerlink.com/content/t341350850360302/ (behind pay-wall)
G.V. Chilingar, L.F. Khilyuk, O. G. Sorokhtin. Cooling of Atmosphere Due to CO2 Emission. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, Volume 30, Issue 1, January 2008, pages 1‑9

I am delighted that this simple and clear but authoritative statement of the reality of the “greenhouse effect” has been posted here. Too many inaccurate statements to the effect that there is no greenhouse effect have been published recently, and they do not deserve to be given any credence. The true debate in the scientific community is not about whether there is a greenhouse effect (there is), nor about whether additional atmospheric CO2 causes warming (it does), nor about whether CO2 concentration is rising (it is), nor about whether we are the cause (we are), but about how fast CO2 concentration will rise (for a decade it has been rising at a merely-linear 2 ppmv/year, against the IPCC’s projection of an exponential increase at today’s emission rates), how much warming a given increase in CO2 concentration will be expected to cause (around a third of what the IPCC projects), whether attempting to mitigate future “global warming” will make any real difference to the climate (it won’t: remember Canute), whether the cost of forestalling each degree of “global warming” will be disproportionate to the climatic benefit (it will), and whether focused adaptation to any change in the climate, where and if necessary, will be orders of magnitude cheaper than trying to prevent that change from occurring in the first place (yes).

Dave Dardinger

Thus, the warming is a result of decreased cooling rates.

This is a bit misleading. As you point out later, the total heat released to space is going to be the same eventually. And the amount of radiation released by the surface will actually increase to include the increased amount of long-wave radiation downward. What’s really changed is the ability of the atmosphere to absorb additional heat because of the increased amount of GHGs in it. This means both the surface and the lower atmosphere will warm (if feedbacks are ignored.)


Is it possible to discuss briefly the effects of changes in the night sky temperature? (I say night sky only because it is easier to visualize, but it is in fact a twenty four hour effect).
As a side note to my interest in studying night sky radiation as an energy source for heat engines is that the temperature of the sky at the galactic plane is quite different than what it is away from the plane, and that the alignment of this plane with the earth’s equator is cyclical over time. This periodic alignment (and other celestial alignment variations) exposes the equatorial earth to longer periods of warmer areas of space and of course the poles to cooler areas, and this, it seems, should affect the ability to cool by radiation.
This question occurred to me because the article discusses the thermal properties of the sky as an unchanging component of the process. Surely in my lifetime it will be, but over the period of time important to climate this may be non-trivial.

Josh Grella

Though I agree with the general idea written about here, I still have a few questions about the greenhouse effect that I haven’t seen addressed anywhere yet (perhaps I just missed it along the way). If greenhouse gases increase, would they not absorb incoming IR as well as outgoing IR? If they do, how do we determine which IR they abosorb at what rate? Also, since CO2 and other gases can/do emit IR in all directions, how do we determine where the radiation emitted goes or is it just assumed that it is emitted in all directions at the same rate/proportion? Is it easier to emit IR outward, sideways, down, any other direction depending on which layer of the atmosphere said greenhouose gas is in? Is all or some of this part of the great unknown at this point?


The weakness in all this seems to me to be the impression I gain that this is all just theory… there MUST be warming because, based on the line of reasoning, it seems to make sense. Is there any experimental method or data that actually confirms that the theory is valid? Yet some of the other theories that have been circulating have also seemed to make sense. Frankly, having spent countless hours reading on this (excellent) site, I have come to the conclusion that even the most sincere analysts and philosophers here are still dealing out opinions and theories that, while interesting, still fail the test of hard science in that nothing can yet be proven. My own skepticism goes beyond just AGW to encompass the entire field of the related science. The actual reliable knowledge here is still dwarfed by the vast unknown. Sorry guys..

Theo Goodwin

Is it not true that your explanation is based on the assumption that CO2 molecules are distributed randomly in the atmosphere? Is it not true that there have been no experiments to test the assumption that CO2 molecules are randomly distributed throughout the atmosphere?

John Prendergast

Lord Kelvin’s second Law lof Thermodynamics paraphrases as heat flows from a hotter body to a colder body. Thus heat from earth’s surface and lower atmosphere must flow to a colder body, perhaps the 0.389 parts per million of CO2 in the atmosphere. However CO2 does not radiate heat to space or back to earth in certain fairly narrow wave lengths. This means we have lot of hot CO2 floating around in the atmosphere, don’t we? No we don’t, becuase hot CO2 molecules pass on their heat to cooler fuller spectrum radiating nitrogen and oxygen molecules. The very slightly heated Oxygen and Nitrogen molecules radiate more energy to space than they did before. Thus CO2 may have an effect but it is going to be very very small until the atmosphere gets to about 13% Co2 when CO2 molecules will start to have to try harder to pass on heat to oxygen and Nitrogen and Helium and Argon molecules.
Of course water vapour mucks things up, there are about 2790 times more water vapour molecules in the atmosphere than there are CO2 molecules and water vapour acts both as a solar sheild/reflector as well as an emitter when not in clouds formation. Water vapour also blocks heat radiation in same frequencies as CO2, again a very small part of the radiating spectrum.
Please stop knocking CO2 – it is free plant food. We need every bit of growing power as earth gets fuller of people.


And then… then there’s night. That would be what half of the planet is experiencing at any one time.
Has anyone tried using a satellite to measure IR radiation on the night side? If night time IR emissions are dropping, then I’d accept that “something” is happening. But as it is, “nothing” out of the ordinary is happening.
Any attempt to show “something” will continue to fail as long as heat continues to radiate away on the night side. That would be the major mechanism of the planet’s temperature self-regulation.
Of course the “greenhouse effect” is real, and of course H2O is the overwhelmingly dominant factor. The currently popular fantasy about CO2 “tipping” the balance in some dramatic fashion is ludicrous, and ignores historically significant CO2 levels that did not (and can not) cause any of these “tips”.
If only some of these people would stand back and see how insane the concept of runaway “feedbacks” is at the gas percentages we’re talking about… especially in the context of an atmosphere that has remained relatively stable for BILLIONS of years.

Stephen Wilde

I think this old article by me holds up pretty well to date :
“Greenhouse Confusion Resolved”
and this is especially for Enneagram:
“The Hot Water Bottle Effect”


Claes Johnson says:
July 23, 2010 at 8:35 am
“I question the analysis by Herman and Pielke in […]”
Great to see you here, Prof. Johnson! I guess your argument (ignoring the low frequency backradiation) is the classical thermodynamics position. My model of a “CO2 fog” that redistributes the “backradiation” around until an quilibrium is reached practically has the same effect: As the radiation in this absorption band goes back and forward in all directions, it practically cancels out, and that is exactly what your argument says (that it’s irrelevant).
Yours is the general view of energy balance, mine – or Dr. Pielke’s – looks at individual rays and tries to figure out the system dynamics.


Reading some of the comments suddenly makes me feel sympathetic with the few warmists that read sceptical blogs.
…and that is an amazing feat…