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During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere.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.
If the only thing to consider was W/m2 then it should be hottest near the transmitting antenna of 50000 W (fifty thousands) radio stations. Like WLS in Chi-town. There are 2.6million sqr m within a square mile of the transmitter. So .019 W/m2 fall on this area 24 hours a day all year. Plus if you add in other stations and backradiation from CO2 those areas must be boiling.
TomVonk says:
July 26, 2010 at 6:07 am
.Btw don’t fall for this “thermalization” garbage either .
If it is true that excited CO2 gives energy away to N2 by collisions , it is also true that N2 excites unexcited CO2 by collisions .
And the two rates are exactly equal in LTE !
So it is trivial QM textbook knowledge that CO2 absorbing IR does not “heat” the atmosphere in any usual sense of the word “heat”
And even if like Phil is saying the emission time is much longer than than the mean time between collisions , it is absurd to say like he does that there is a net energy transfer from CO2 to N2 by collisions .
Think 10 seconds and you will find easily why saying that there is a net energy transfer between 2 molecular species in LTE is ridiculous 🙂
I’m glad you added the smiley otherwise people might think you were right!
Think for 1 second and you’ll realize why Vonk’s wrong.
CO2 in a dry atmosphere is the only chemical species capable of absorbing 15μm radiation in doing so it has acquired extra vibrational and rotational energy. Experiments show that this excess energy is very rapidly lost before the molecule has a chance to lose it by radiation. This is the process known as thermalization, if it didn’t occur then the extra energy would just radiate away and the air would not heat up, this is not what’s observed. What Vonk is misled by is that N2 and O2 also transfer heat to CO2 molecules by collisions, however this still means that the lifetime of an individual vibrationally excited CO2 molecule (whether excited collisionally or radiatively) is orders of magnitude shorter than the mean time required to emit a photon. So the net effect of the absorption of 15μm radiation by CO2 in the lower atmosphere is that the atmosphere heats up and emission of IR by CO2 is very low (the whole process is statistical so there will always be a few molecules that will emit before they can be collisionally deactivated).
[reply] But we don’t live in a dry atmosphere. RT-mod
TomVonk says:
July 26, 2010 at 6:07 am
If it is true that excited CO2 gives energy away to N2 by collisions , it is also true that N2 excites unexcited CO2 by collisions .
And the two rates are exactly equal in LTE !
Well, but is the atmosphere in a thermodynamic equilibrium after all?
I know when the nights are clear and humid the ground cools at a smaller rate and the air temperature at 2 meters is warmer than when the nights are clear and dry.
It is evident that H2O is changing the heat retention properties of the air in a quantifiable and calculable way. I do not need the quantum framework to do that.
But, if I am interested to see why the addition of 0.4% H2O in the total atmosphere makes such a difference, the quantum picture helps in understanding. In this picture the equilibrium is broken by the selective capability of H2O to absorb and redistribute infrared energy rather than being transparent to that particular one as N2 and O2. It changes the mean free path of the infrared photons. In the same way that fog changes the mean free path of the optical photons. Am I wrong?
Joel Shore (July 23, 2010 at 8:00 am):
Thanks for taking the time to respond.
We seem to agree that the word “heat” makes ambiguous reference such that one concept referenced by the word is bound by the second law and another is not. It follows that the proposition “heat flows up a temperature gradient without being pumped” is true and is false, thus violating the law of non-contradiction. No proposition that violates this law is falsifiable, for this proposition is true and false. Thus, the proposition “heat flows up a temperature gradient without being pumped” is not falsifiable. This proposition is a premise of “the greenhouse theory” that is described by Herman and Pielke. It follows that “the greenhouse theory” states a proposition that is not falsifiable. A theory that is not falsifiable is not a scientific theory, by the definition of “scientific.”
It seems to me that the argument made in the preceeding paragraph is logically impeccable. Whether it is G&T or Herman and Pielke that are right is unrelated to the question of whether “the greenhouse effect” is falsifiable. Further, your implicit claim that the ambiguity of reference by the word “heat” is “slight” is inaccurate in reference to the proposition “heat flows up a temperature gradient without being pumped”. In reference to this proposition, the ambiguity is total.
Cordially, Terry Oldberg
Phil. says:
July 26, 2010 at 8:42 am
[reply] But we don’t live in a dry atmosphere. RT-mod
Some do, but it’s immaterial to the physics, I just put it in there in an attempt to avoid irrelevant discussions about absorption by water!
[reply] Water vapour is the main greenhouse gas in the Earth’s atmosphere. That fact affects the scale of the effect you are discussing.
Phil. says:
July 26, 2010 at 8:42 am
If what you say: “So the net effect of the absorption of 15μm radiation by CO2 in the lower atmosphere is that the atmosphere heats up and emission of IR by CO2 is very low …” is correct (and I do not dispute what you say), what then exactly is this “back radiation” (i.e., IR radiation absorbed by greenhouse gases that is re-radiated in a downward direction thus heating the Earth’s surface) we hear so much about? If the Earth’s surface is warmed by the capture of IR radiation leaving the Earth’s surface and then being returned to the Earth’s surface, isn’t it more appropriate to call the process “back-conduction”, or possibly “back-convection” if the IR heating produces translational movement of air molecules?
Chad Woodburn says:
July 25, 2010 at 7:41 pm
I still have a question which I have asked before, but people decided to nitpick over the illustration I gave instead.
MY QUESTION IS: While CO2 blocks radiation from escaping from the atmosphere, thereby producing a greenhouse forcing, 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?
__________________________________________________________
I am a lowly chemist but I will try to answer the question.
The sun is much hotter than the earth. The black (and gray) body radiations from a hot object are a function of the temperature of the radiating body. Because the sun is so much hot that the earth it emits energy in the extreme ultraviolet, ultraviolet, visible and near infared wave bands. The earth emits in the infrared wave bands only. There is very little overlap in the emitting wave bands.
see these graphs:
Total sun and earth emissions note sun is much larger than earth’s.
Total amount of irradiation received by earth from the sun and the amount emitted from the sun. Note the amount received = amount emitted, otherwise the earth’s temp would continually increase. you can see there is very little overlap in wavelengths: click
Solar spectrum only
Astronomers Get the Spectrum of Earthshine
Phil. says:
July 26, 2010 at 10:10 am
Phil. says:
July 26, 2010 at 8:42 am
[reply] But we don’t live in a dry atmosphere. RT-mod
Some do, but it’s immaterial to the physics, I just put it in there in an attempt to avoid irrelevant discussions about absorption by water!
[reply] Water vapour is the main greenhouse gas in the Earth’s atmosphere. That fact affects the scale of the effect you are discussing.
Not at 15μm (and not in many parts of the atmosphere either), in any case if the mean emission time of H2O is longer than a few nsec the same physics works there.
What is it with you guys, I simplify the physics to make it as straight forward and intelligible as possible and you complain? Look at the big picture this is how it works.
PDF (1.8 MB)
Authors
Roy Clark, Ph.D.1
1 1336 N. Moorpark Road #224, Thousand Oaks, CA 91360 USA
Abstract
Energy transfer at the Earth’s surface is examined from first principles. The effects on surface temperature of small changes in the solar constant caused by the sunspot cycle and small increases in downward long wave infrared (LWIR) flux due to a 100 ppm increase in atmospheric CO2 concentration are considered in detail. The changes in the solar constant are sufficient to change ocean temperatures and alter the Earth’s climate. The surface temperature changes produced by an increase in downward LWIR flux are too small to be measured and cannot cause climate change. The assumptions underlying the use of radiative forcing in climate models are shown to be invalid. A null hypothesis for CO2 is proposed that it is impossible to show that changes in CO2 concentration have caused any climate change, at least since the current composition of the atmosphere was set by ocean photosynthesis about one billion years ago.
I didn’t have the $18 bucks to buy the article. Please note his “…the use fo radiative forcing in climate models are shown to be invalid.”
PDF (1.8 MB)
Authors
Roy Clark, Ph.D.1
1 1336 N. Moorpark Road #224, Thousand Oaks, CA 91360 USA
Abstract
Energy transfer at the Earth’s surface is examined from first principles. The effects on surface temperature of small changes in the solar constant caused by the sunspot cycle and small increases in downward long wave infrared (LWIR) flux due to a 100 ppm increase in atmospheric CO2 concentration are considered in detail. The changes in the solar constant are sufficient to change ocean temperatures and alter the Earth’s climate. The surface temperature changes produced by an increase in downward LWIR flux are too small to be measured and cannot cause climate change. The assumptions underlying the use of radiative forcing in climate models are shown to be invalid. A null hypothesis for CO2 is proposed that it is impossible to show that changes in CO2 concentration have caused any climate change, at least since the current composition of the atmosphere was set by ocean photosynthesis about one billion years ago.
I didn’t have the $18 bucks to buy the article. Please note his “…the use of radiative forcing in climate models are shown to be invalid.”
http://www.appinsys.com/GlobalWarming/EPA_Submission_RClark.pdf
Here is a link for another paper by Dr. Clark with the summary about radiative forcing.
Terry Oldberg:
Thanks for your reply. Yes, different people tend to use the word “heat” slightly differently. (E.g., some use it only in a macroscopic sense so that heat must flow from colder to hotter [in the absence of work] whereas some use the term “net heat” to refer to this macroscopic heat concept and then talk about the various radiative transfers represented by the Steffan-Boltzmann Equation as “radiative heat flows” or something of the sort.) Like ambiguities in terminology that exist in ***ALL*** fields of science, this has the potential to create some confusion but that confusion is easily cleared up by simply stating the sense in which one is using the terms. I know of no field of science free from such confusions and people are discussing what is the best terminology and pedagogy all the time without resorting to stating that a field has foundational errors and that the theories in the field are thus unfalsifiable.
And, I don’t even think that confusion in terminology is the main problem here. The main problem is that G&T have claimed in response to our comment on their paper that “The correct question is, whether the colder body that radiates less intensively than the warmer body warms up the warmer one. The answer is: It does not” and other people have made similar claims. These claims are demonstrably incorrect, as Herman & Pielke and Roy Spencer and Willis Eschenbach and many others have pointed out, at least if by “warms up” one means (as in the greenhouse effect) that the presence of the colder body makes the steady-state temperature of the warmer body higher than would be true in the absence of this colder body.
There is nothing in any of the models of the greenhouse effect, whether they be “toy models” or full-blown GCMs, that violates the Laws of Thermodynamics. And, no matter how one might argue about what the best way to use various terms like “heat” in describing these models, it will not change that simple fact.
Cheers,
Joel
mkelly: Yes, everyone agrees that there is a lot of garbage out there on the internet. You seem to have found some.
I eschew theory replacing experiment. The effect is simple enough to measure. Suspend two objects at different temperatures in a vacuum chamber and measure the rate of cooling. Remove one object and measure again.
An error I see made all too frequently is forgetting that electromagnetic radiation exhibits wave/particle duality and which way to treat it depends on context. In general electromagnetic radiation propagating through a vacuum are treated as waves. They are treated as photons generally only during certain interactions with matter. The wave nature of EMR has some weird effects associated with it like interference, standing waves, and so forth when they meet.
So no, I don’t believe there is any spooky action at a distance going on with 2LoT but I know that the wave nature of EMR makes your photons passing in the night theory bereft of much connection to physical reality or any real understanding of EMR. The higher amplitude wave coming from the warmer object meets the lower amplitude wave coming from the cooler object and simply decreases the amplitude of the higher power wave. This takes place in the vacuum between the two objects.
Likewise, I don’t think it’s magic that when I have pump pushing water uphill in a pipe and I add head to the pipe that the increased pressure isn’t making more of the water molecules at the end of the pipe fall all the way back down to the pressure source.
Like I said, this is easily settled by experiment though. I could be wrong and experiment will prove that one way or another. Electromagnetic wave theory was far from intuitive when took a course in it 30 years ago so I could be mistaken.
For once I agree with Joel but only on this specific point.
In reality we have three ‘bodies’ to consider namely Earth, it’s oceans and it’s air.
The Hot Water Bottle Effect of the oceans is so large in relation to the Greenhouse Effect of the air that the latter should be ignored. It is the oceans that make the troposphere so much warmer than it ‘should’ be.
CO2 being but a tiny portion of the air a change in quantity can have no measurable effect at all.
Furthermore the temperature of the troposphere is set by the density and pressure differentials between ocean air and space and not merely by the composition of the air.
No change in the composition of the air that fails to affect total density and pressure of the air or the ocean can have any effect on the equilibrium temperature of the troposphere.
If the optical depth of the atmosphere has not changed for 61 years then CO2 increases have failed to affect total densities and pressures because the speed of the hydrological cycle changed to negate the CO2 effect.
Is Miscolczi right or not ?
Either optical depth has changed or it has not. Which is it ?
Bingo! Most everyone here is talking about EMR in quantum unit carriers (photons) when they should be talking about waves. I cut my teeth in EMR theory in the radio and microwave portions of the spectrum which cannot be properly understood without understanding wave propagation. Light is no different than radio waves except in wavelength. Waves are a lot harder to understand as they act in very non-intuitive ways where photons can be treated more or less like a ping pong ball.
anna v says:
July 26, 2010 at 5:34 am
John Finn says:
July 26, 2010 at 2:25 am
You have once more described Peden’s oven, the paradoxical chicken that cooks by itself because of the reflected radiation:
No I haven’t. The planet-atmosphere has an external heat source – it’s sun.
@Stephen Fisher Wilde
You’re making the most sense here IMO.
I’m not an optical guy so when you mentioned optical depth I googled optical depth co2 global warming and the second hit was a discussion of a paper
Greenhouse Effect in Semi-Transparent Planetary Atmospheres by Ferenc M. Miskolcziby
At first blush it appears solid and made me want to clarify some things I’ve written.
First of all I said the greenhouse effect is real and based that on no more than the average temperature of the moon measured experimentally by two different Apollo missions which placed thermocouples at the surface and at various depths up to 3 meters in regolith and recorded the results over a period of years. Below 25 centimeters the thermal gradient disappeared and the measured temperature was negative 23C. The earth and the moon are made of the same stuff and sans atmosphere would have substantially similar albedos. With an atmosphere that allows oceans and clouds and ice the earth’s albedo is about 0.30 compared to the moon’s 0.12 so absent any so-called greenhouse effect we should expect the earth to be somewhat colder than the moon.
The average temperature of the ocean is about 4C which I believe is the true average temperature of the earth’s surface, averaged across glacial and interglacial periods. So the claim in the OP that greenhouse warming of 33c is probably close enough to correct to not be worth arguing about.
I also said that CO2 greenhouse effect is real but I wasn’t clear that it’s real only in isolation — if everything else remains the same. The Miskolcziby discussion referenced above made want to clarify. CO2 doesn’t exist in a vacuum. Changing its concentration can’t be considered in a vacuum. So the long and the short of it is that greenhouse warming is real, Co2 greenhouse warming is real, but CO2 probably makes no net contribution to global warming in the present or near future context and in no case is anthropogenic CO2 going to have any measurable effect. Possibly it becomes an important greenhouse gas in “snowball earth” episodes.
I think we are in agreement on the above. I just wanted to be sure we’re on the same page.
Dave Springer says:
July 26, 2010 at 3:54 pm (Edit)
Greenhouse Effect in Semi-Transparent Planetary Atmospheres by Ferenc M. Miskolcziby
That’s Miskolczi.
More here: http://tallbloke.wordpress.com/2010/01/04/why-the-sun-is-so-important-to-climate/
Dear all…
I’d like to contribute a little on this issue.
First of all, AGW is based on false conceptions and incomplete information about the physics of heat transfer.
I don’t understand why AGW proponents take the carbon dioxide as the cause of a climate change invoking its absorptive-emissive power because, through experimentation and observation of natureal phenomena, it has been demonstrated the gas is physically incompetent for causing a warming of the atmosphere.
A brief and simple calculation of the emissive power of the carbon dioxide at its current mass fraction, taking into account the results of many experiments done by reputable scientists and engineers like Hottel, Leckner, Sarofim and many others, the total emissivity and absorptiviy of the carbon dioxide is quite insignificant.
The following formula is for calculating the total emissivity of the carbon dioxide:
ΔE = [[ζ / (10.7 + 101 ζ)] – 0.0089 ζ ^10.4] (log10 [(pH2O + pCO2) L] / (pabsL) 0) ^2.76
Considering the data obtained by many researchers on this matter, the total emissivity of the carbon dioxide is low. It is 0.0017.
This value is very important for calculating the amount of energy that the carbon dioxide absorbs and emits each second. Given the specific heat capacity of the carbon dioxide at its current density and temperature, which is of the order of ~871 J/Kg K, the carbon dioxide is not the cause of any change of the Earth’s climate.
The formula for obtaining the amount of energy transferred by radiation between two thermodynamic systems is as follows:
Φq/s = e σ (A) [(Ts^4 – Tg^4)]
For example, at an atmosphere temperature of 310.4K (27 °C), the usual temperature in Summer at my location, and a surface temperature of 340.65 K (67.5 °C) the energy emitted by the carbon dioxide is 0.403 W*s.
On the contrary, the water vapor emitts 102 W*s.
It is clear what is the main protagonist in the warming of the Earth.
Besides, the oceans, the land and the subsurface materials are the fundamental thermodynamic systems of the Earth that store energy for longer periods than the atmosphere, which, in any case, acts like a conveyor of thermal energy.
On the other hand, the main thermal energy exchange at the boundary layer surface-atmosphere is not by radiation, but by conduction. The energy absorbed by the layer of air above the surface is convected away by the air. The latter happens also with the radiation absorbed by the atmosphere.
Phil. says:
July 26, 2010 at 11:15 am
What is it with you guys, I simplify the physics to make it as straight forward and intelligible as possible and you complain? Look at the big picture this is how it works.
No Phil, this is the BIG picture of how it works:
The sun heats the ocean, the ocean heats the atmosphere, and the atmosphere loses heat to space while the convection of evaporated ocean water regulates the speed at which the ocean cools. That’s the big picture. Any co2 in excess of around 120 parts per million is pretty much along for the ride, because the window of opportunity it has to do anything exciting is pretty small compared to what water vapour does.
Now, within that bigger picture, what do you estimate the scale of the radiative forcing involving 0.039% of the atmosphere compared to the energy flows outlined above to be?
@Gail Combs July 26, 2010 at 11:10 am
The question was about which part of the solar specturm is blocked by greenhouse gases on the way in.
Comparison of solar spectrum at top of atmosphere and at the surface answers that question and also illustrates the difference between water vapor and CO2. This graph overlays power spectrum at top and bottom of the atmosphere in full sun.
http://en.wikipedia.org/wiki/File:Solar_Spectrum.png
H2O does all the heavy lifting in both incoming spectrum as well as in LWIR at night as it boxes in CO2 on either side and overlaps it as well. You can’ t see the overlap because the power spectrum is so small in the CO2 band.
It’s untrue that sunlight has no LWIR component. It does and you can see it in the graph above.
tallbloke says:
July 26, 2010 at 4:57 pm (Edit)
Now, within that bigger picture, what do you estimate the scale of the radiative forcing involving 0.039% of the atmosphere compared to the energy flows outlined above to be?
Phil, I see Nasif Nahle July 26, 2010 at 4:52 pm has done the homework I set for you. He has done the quantitative work on co2’s effect. Qualitatively I was going to say it was somewhere between a fart in the wind and a storm in a teacup. Hi Nasif 😉
Case closed.
Hi, tallbloke! 🙂
Published work shows that a third of the downward longwave flux at the South Pole surface is from CO2. This paper goes into measurements of the spectrum to prove it. It is hard to dispute that level of detail.
http://journals.ametsoc.org/doi/pdf/10.1175/JCLI3525.1
from Abstract “About two-thirds of the clear-sky flux is due to water vapor, and one-third is due to CO2, both in summer and winter.”
Can we move past this argument about CO2 being insignificant now?