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During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere.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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Andres Valencia says:
July 23, 2010 at 4:57 pm
“Am I right to think about G&T that:
A possible way for atmospheric “greenhouse gases” to warm a planet could be by temporarily delaying some escape of heat?
Infrared absorbing gases in the atmosphere could slow the cooling of the Earth?”
Almost exactly. The gases (including the IR absorbing ones) have a thermal capacity and they are poor conductors. That’s why they slow the cooling. The radiation freaks are ignoring this part of the equation!
Just in case this hasn’t been linked:
http://hockeyschtick.blogspot.com/2010/07/must-read-global-warming-alarmists-in.html#comment-form
BTW, Herman and Pielke Sr. don’t have any qualifications that exceed G&T or some of the others I linked to. So the Jury is still out, I think. We have a hypothesis not a theory; no empirical evidence; DEFINITELY not proven!
Guest post By Ben Herman and Roger A. Pielke Sr.
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.
The more you people write, the more you reveal yourselves to be the pseudoscientists you are. Who’s paying you to push that line of crap? Whomever it is must be paying you well! Are you hierodules in the temple of CACC or CAGW?
[1] The natural state of all matter is: REST. Ergo, gasses DO NOT ABSORB –AND RETAIN– ANYTHING.
Hell, it doesn’t ABSORB anything!
Certainly CO2 molecules may be excited to a higher energy level, but as soon as the energy source either diminishes or ceases, the resonance decreases/ceases.
You two make it sound as if the gas acts as a battery of some sort which absorbs —and saves— energy, only to release it at an inconvenient time.
Hell, you even make it sound as if the CO2 “amplifies” the Sunlight!!!
CO2 —just as with other atmospheric gases— acts as an insulator. And while it is true that it resonates with energy of a certain spectra, that in NO WAY implies that it will behave differently otherwise.
Any energy received by CO2 molecules, is released by that molecule consonant with the energy received, and the ability of the atmosphere to accept the energy released.
The Sun is a PRIMARY radiator, and the Earth a secondary radiator. That being the case, when ‘Sun don’t shine,’ then the Earth is THE ONLY source of radiated energy, and NOT the gas.
[2] Now then, since the gas acts merely as a ‘transmission’ medium for a certain spectra, then it may well be said that it DOES NOT retain energy of that spectra, but instead helps to disperse it MORE RAPIDLY than if it were it not in existence — FOR THAT SPECTRA.
Ergo, with MORE CO2 in the atmosphere, the amount of energy reradiated by the Earth is actually facilitated by the CO2 which actually leads to better cooling.
This reciprocity then is beneficial: Even when the Sun radiates at a stronger level, the radiation from the Earth sends even more energy back into space by dint of the fact that the energy from the Sun coupled with the re-radiated energy from the Earth, EXCEEDS the energy received from the Sun, contributing to the space-bound energy.
AND, with no Sunlight —hours of darkness— the CO2 thence facilitates the release of energy into space.
[3] NOW AGAIN: why with all that CO2 locked in the matrices of the polar and glacial ice, isn’t said ice turning to water every time the Sunlight hits the ice?
And WHY aren’t the seas —with all of that entrained CO2— roiling whenever the Sunlight hits them?
And WHY aren’t the lot of us roasting like pigs on a spit whenever the Sunlight hits us, if only that the atmosphere is virtually flooded with that dreadful CO2 gas?
anna v
I putter with the toy Earth a bit in 1-d with some fairly sophisticated in my spare time. I use a combination of stefan’s law and a full bore hitran IR database radiative power transfer application along with a model atmosphere from 1976. It doesn’t deal with particulates but it seems to do a good job on spectral analysis when compared with actual high resolution spectrums.
It provides some interesting things IMHO when combined with some concepts from Keihl and Trenberth 97.
In essence we get an averaged surface T and emission of 288.2K and 391w/m^2. We have an averaged incoming solar of 341w/m^2 with about 0.305 of that reflected away due to albedo, leaving 239w/m^2 solar power being absorbed by Earth’s surface & atmosphere. Simple energy balance demands that there must be an averaged value of 239w/m^2 emitted. Simply put, there must be an average of 391-239 = ~150 w/m^2 of outgoing power which must be absorbed without being reemitted. Note that about 107 w/m^2 is all that ghgs absorb so the balance due to clouds must be the difference, about 43 w/m^2.
In answer to your question about n2 and o2, I’ve modeled no co2 and no2 h2o and that removes about 99 of the 107 w/m^2, leaving about 8 w/m^2 absorption due to all other small ghg contributors.
One can establish a sensitivity – although not quite the same as (mis)defined by the ipcc by taking the 33deg C rise and dividing by the 150 w/m^2 ‘forcing’ power. That gives us 0.22 deg C rise per W/m^2 power absorption increase and is the actual Earth’s sensitivity factor.
Note that a straight radiative ‘sensitivity’ can be done by taking the emission of 239 divided by 391 – the emission from the surface to get the fractional estimate of power leaving the surface and escaping. That’s about 0.61 so divide that into 1 W/m^2 gives a needed increase of 1.6w/m^2 emitted from the surface in order for 1 w/m^2 to escape and at 288.2k, that corresponds to a T increase of around 0.29 deg C rise per W/m^2 absorption increase. This suggests that a net negative feedback is present as the needed change is less than a straight radiative change.
A doubling of co2 comes out with a 3.7 W/m^2 increase in absorption at the tropopause (11km and over the spectrum range of 0 to 75 um). This gives a (n ipcc) sensitivity of 3.7 x 0.22 = ~0.8 deg C rise per co2 doubling. If one resorts to look at absolute humidity and goes with the climatology assumption that relative humidity stays constant with the change in averaged T, one can assume a 2 deg C rise and come up with only a 13% increase in averaged h2o vapor. That is much less than an h2o doubling so it amounts to around 5.1 w/m^2 when combined with the co2 doubling. This gives a sensitivity for co2 doubling of 5.1 x 0.22 = 1.1 deg C rise- which means that unless there are additional significant effects causing another 0.9 deg rise, that we’ve actually overestimated the additional h2o consequence.
At present we are now below the claimed sensitivity measurement ranges, but only slightly and only if there are no other effects. We are also a long way from the potentially serious high sensitivities claimed by the warmistas. Note that the nice long list of these claimed papers gets quite short when each is held to any scrutiny as each has a rather wide error range and lots of potential problems with methodology or assumptions.
Another factor is the nature of the albedo. With 70% ocean and liquid water, the surface averaged albedo is about 0.08. With 62% cloud cover, that puts the cloud albedo at around 0.22 and clouds themselves with an albedo of around 0.37, significantly less than the sulfur based clouds of Venus. The clouds provide a most interest averaged situation. They’re blocking most of the surface radiation and are emitting essentially a full blackbody spectrum since we’re dealing with droplets of h2o water or ice. I’ve not looked into the emission characteristics of water droplets but they’re not going to be molecular spectrums like that emitted from a gas and I think they’re going to be full bore (or close to it) bb continuum curves (at the characteristic T of the droplets). That means there’s broad band emissions above the altitudes where much of the ghgs reside.
George E. Smith says:
July 23, 2010 at 5:08 pm
The simplest way to see that delaying the cooling process results in a higher temperature, is that during the delay time between energy coming in, and an equivalent energy exiting, the sun is still pouring in energy at a constant rate; so an increment of energy is added to the earth system that grows linearly with the propagation delay of the cooling process, and that must result in the Temperature going up.
If you have a well-mixed mixture of distilled water and ice, the temperature of the mixture will be 0 degrees Centigrade. As you add heat to the mixture, the temperature will stay at 0 degrees Centigrade until the ice has melted. If you add enough heat the ice will melt and the temperature of the water will rise. But during the interval the ice is melting, the added heat does NOT raise the temperature. So I don’t believe that the claim “an increment of energy” must result in “the Temperature going up” is correct.
Ben Herman and Roger A. Pielke Sr.
I find your post confusing. Surely you can present a post more logical and explanatory than your current offering? I’ve given up reading the responses here after reading about 30% of them.
IMHO I believe you would do better service by concentrating your effort into describing the effect that pressure invokes on the speed and type of energy transfer between molecules in a mixed gas. This would lead to a discussion on internal molecular energy (twisting, stretching and bending of bonds, their resonant frequencies and the time-scale that may, or may not, lead to a photon emission).
If you took this approach, it would be easier to explain that GHE (greenhouse effect) is dependant on the time permitted for a given ‘radiatively active’ molecule to either, receive internal energy by irradiation absorption from the EM field and emit a photon to the EM field (re-radiation), or receive internal energy by irradiation absorption from the EM field and passes this energy on to another molecule by ‘collisional transfer of energy’ (thermalisation of EM radiation). At least WRT to OLR (outgoing long-wave radiation), for example, is it ‘outgoing’, or ‘not’!
IOW! If a molecule’s internal energy reduces and it produced a photon it’s not within the ‘greenhouse’, but if a molecule’s internal energy reduces without the manifestation of a photon the energy has added to the general gas kinetic and is within the ‘greenhouse’.
This ‘microscopic’ view may seem to give more ‘focus’ to the definition of GHE, but it also adds complexity. However, I believe that the readership here is up to this and those who aren’t will be helped by those who are.
That received, I think you’ll realise that GHE is dependant on the gas selected and the local atmospheric pressure. Why not post on this?
Best regards, Ray Dart.
This is slightly O/T but I can’t help myself. I had this afternoon off, I was home alone in peaceful quiet and thoroughly enjoying this comment thread. There’s some mighty meaty stuff here! Great reading! I was thoroughly engrossed.
Then my doorbell sounds and my dogs start barking like idiots. I go to my door in disgust and tell my “man killer” Golden Retrievers to sit down and shut up (and quit wagging your tails…that’s embarrassing). I find a kid of about 19, standing all of about 5’8″ with greasy hair with a Sierra Club badge on a lanyard holding a clipboard. He had holes in his earlobes expanded by what looked like huge metal Cheerios. He explained that he was from the Sierra Club and he was here because of the oil spill in the Gulf. Of course I asked if that was the case why he was here in Santa Fe and not down on the Gulf Coast. He said, “Well sir, we’re here looking to recruit new members”. I couldn’t help myself. I’m 6’2″ and I’m already standing on a stoop a good 5″ above him. I leaned in and slightly over him and in my deepest, most menacing voice I said, “I would rather DIE than join the Sierra Club.
His smile vanished and he beat a hasty retreat to the street as fast as he could go without breaking into a run. Childish, perhaps…but hey…you find your fun where you make it!
Tallbloke:
“Mosher and the warmists say co2 warms the atmosphere. Pielke and I say it slows the rate of cooling of the atmosphere. You say “it doesn’t matter”.”
I’m pretty sure there’s no disagreement between Pielke and “warmist” scientists on the basics of how the GH effect works, so I guess that claim of yours is just a strawman.
I think you’re being a bit unfair on Mosher, the analogy I’d use is if you’ve got and electric blanket but then put more blankets over the top, do the additional blankets work to help increase how warm the bed is? no one would be claiming that the extra insulation (blankets or CO2) is a heat source, but a warmer bed (or Earth surface) is the result.
Tallbloke responds to Basinger as follows:
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’.
So, Tallbloke, is it wrong to say that CO2 molecules capture radiation from Earth’s surface and then emit radiation randomly so that near half what they admit goes to Earth’s surface? If this description is correct then how can it be that the emitted radiation does not heat the Earth’s surface?
This chart is illustrative.
http://en.wikipedia.org/wiki/File:Solar_Spectrum.png
Note how much more power in the infrared spectrum is absorbed by H2O compared to CO2.
Water vapor accounts for some 95% of GHG warming. The mechanism is the same. There are interesting differences however.
Water vapor can vary a lot from region to region and in the same region it can vary a lot and do it quickly. CO2 doesn’t vary nearly as quickly or as much.
Water vapor also also forms clouds and ice. CO2 doesn’t. Cloud formation causes cooling in at least two different ways. CO2 of course doesn’t form clouds. When water vapor condenses into a cloud it releases a lot of latent heat of vaporization. That heat was picked up at the surface where the water evaporated. The water cycle works like a heat pump with the cold side on the ground and the warm side in the clouds. And then of course a cloud is has a much higher albedo so it bounces a lot of the visible spectrum back out into space before it reaches the surface. Ice of course also has high albedo.
Albedo is a big flaw in global circulation models (GCM). The earth’s average albedo is difficult to measure even today and various different attempts to measure it are not in satisfactory agreement. We do know it varies however and but the GCMs model albedo as a constant. Moreover, the value assigned to the constant in different models (the guesstimates) differ greatly. It’s bascially a fudge factor that the model maker gets to adjust but so long as it’s a constant in the model where it’s a significant variable in reality it mucks up the model in one way or another no matter what constant value they assign. Neat huh? Hide the albedo.
These aspects of cloud formation are very poorly modeled in the so-called Global Circulation Models and they have huge potential for variable effect.
Your rebuttal of the two misconceptions is spot on, as far as I can see.
However, your conclusion doesn’t follow, except in the trivial sense that more GHCs imply more warming covers warming of any amount, including infinitesimal amounts.
You are also correct that the Earth’s temperature in excess of 255K is due to GHCs. However, if “more warming” at the current temperature and concentration of GHCs means a significant amount if warming, then you have not made that case and I believe the evidence is completely against it.
Steve Goddard’s adiabatic lapse rate argument makes much more sense. Personal observations that anyone can do, such as watching an eagle rise on a thermal, should be enough to convince you that convection completely dominates heat dissipation from the Earth’s surface and does so on a scale far too small to be accounted in the expensive supercomputer climate models. If this is so, and it certainly seems as if there is overwhelming evidence that it is, then all fear of greenhouse disasters is entirely misplaced.
Why oh why does nobody address simple heat storage effects? The Earth is NOT a simple blackbody that emits exactly what it absorbs. It absorbs and stores heat. The SB equations don’t accomodate this fact, so they cannot be used to predict the temperature of the planet without GHGs. This very obvious fact is not being addressed by those who think they are “in the know.”
Most serious sceptics recognise that the greenhouse effect is a physical reality, however they also recognise that totally unrealistic and unphysical to consider this effect in total isolation.
Basic physical principles tell us that any increase in the downward IR radiation in the atmosphere (e.g. caused by increasing levels of CO2) must originate in the levels of the atmosphere where the absorportions by that particular green-house gas are not saturated. This corresponds to the upper troposphere for CO2 (and water vapor).
In its simplest terms, it means that it requires increasing levels of either CO2 and/or water vapour in the upper (tropical) troposphere, in order for their to a significant warming of the atmosphere due to green-house gases.
The truth is that increases in CO2 levels in the atmosphere result in greater amounts of IR radiation being reflected back upon the Earth’s ocean surfaces. This additional energy leads to a greater level of evaporation from the Earth’s tropical oceans.
This additional evapouration at the oceans surfaces leads to an additional deposition of energy in the mid level (tropical) troposphere through the dual processes of the latent heat of evaporation (at the ocean surface) and condensation (in the tropical thunderclouds). This deposition of energy warms all levels of the (tropical) troposphere, with the level of warming with altitude being set by the relative contributions of the dry and wet adiabatic lapse rates.
Many people seem to missing the crucial point that the increase in convective overturning in the (tropical) troposphere (caused by increasing evaporation
from the oceans surface and condensation as rainclouds) results in the pumping of massive amounts of de-humdified air into the upper (tropical) troposphere.
This lowers the specific humidity (mass of water vapour per 1 kg of air) in the upper reaches of the tropical tropsphere.
It doesn’t take a genious to see that the resultant decrease in water vapor ( a dominant green-house gas) in the same level of the atmosphere where increasing amounts of
of CO2 is having its greatest impact on warming the atmosphere produces a MASSIVE NATURAL NEGATIVE FEEDBACK MECHANISM, that effectively nulifies CO2 ability to warm the atmosphere.
This simple physical model is backed up by direct radiosone observations which show that:
a) the overall (i.e global) IR optical depth of the atmosphere has not changed in the
last 61 years
b) that the IR optical depth of the atmosphere appears to be controlled by the column
density of water vapour (NOT CO2).
c) the specific humidity of the upper troposphere has been systematically dropping
over the last 30 – 40 years.
When will people start waking up to these simple realities?
Say you have one of those insulated coffee cups. When you put hot coffee in it do you say the cup heats the water? Of course not. The keeps it warm long.
CO2 does the same thing as the cup.
Oops – meant to say “the cup keeps the coffee warm longer”
It is interesting to see this as proof of the “obvious”:
“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.”
My understanding is that the atmosphere has density, this density causes compression, compression causes an increase in temperature. How much of the 33 degrees warmer is the compression? For an idea, just 30,000 feet up in the air the temperature outside the cockpit of an aircraft is frequently -30f to -50f. If the surface air temperature is 70f this is a difference of 100 to 120 f. Sorry, but I am not going to be duped into the greenhouse effect, the amount of radiation escaping from the surface of the earth at the wavelengths for which it can be absorbed by the “greenhouse gasses” are fully 100% saturated by 10 feet elevation, moving that 10 feet of elevation down to 5 feet or even 2 feet is not going to significantly increase the temperature of the atmosphere, which is more than 100,000 feet deep.
“CO2 does the same thing as the cup.”
And if you put a vacuum between the coffee and the cup, it stays warmer much longer. So just what is your point?
The core issue here apparently is: more CO2 slows down the IR escape to space. Then, TIME is the variable I see absent from the equations regarding irradiation, either downwell radiation or to outer space.
Photons travel at the speed of light, so a photon irradiationg from the surface will be about 300.000 km from Earth’s surface in the first second. And it is not coming back.
How much time it takes for a molecule to reirradiate a photon after receiving it? How much does it take to go down a Fermi level and radiate a new photon? Picoseconds, Nanoseconds, femtoseconds? Has anyone measured that? And how?
Can there be calculated the number of molecules a photon will impact before going out to space? The atmosphere is not a solid block of gas molecules, so quadrillions of photons will be escaping to outer space without hitting any molecule. On the other hand, millions of photona can impact several quadrillion molecules before finally escaping without a possibility of return.
If someone could calculate that, making an overall average and adding the delay in reirradiation could give an idea of how much -(if it ever happens)- GH gases retard radiation going to outer space. And those gases non GH as oxygen and nitrogen, will absorb the photon but will only get rid of it by conduction! And the sheer difference between GHG and O2 and N2 is humongous, so the chance of giving away the energy by trasnferring the heat to a CO2 molecule is negligible. This complicates things further.
Uncertainties are too broad here. I wish someone had an answer. I hope it is not I the only one who jumps in a huge mattres of ignorance.
Mods
As pointed out by George (above) I made a typo in the following:
Phil. says:
July 23, 2010 at 12:58 pm
…….”In fact for CO2 the time it takes to emit a photon from the excited state is much shorter than the mean time between collisions in the lower atmosphere so the most likely fate of the excited state is to transfer kinetic energy to the surrounding gases via collisions. Higher up in the atmosphere collisions become less likely and therefore emission of radiation more likely.”
It should be ‘longer’ not ‘shorter’. Can you fix it since it doesn’t make sense otherwise.
REPLY: I have fixed it for you. – Anthony
Thanks Anthony, Ben Herman and Roger A. Pielke Sr.; Great article!
Thanks DirkH and jae, I am using the delay concept to limit the scope of my article on the G&T paper published at “Climate Change; The cyclic nature of Earth’s climate”, at http://www.oarval.org/ClimateChange.htm
Clear Skies
Dr. Dave says:
July 23, 2010 at 7:03 pm
“I would rather DIE than join the Sierra Club”.
Send the Sierra club recruiter to Los Osos, CA. I’d like to confirm your feelings.
“The rest of the processes, including convection, conduction, feedbacks, etc. are too complicated to discuss here and are not completely understood anyway.”
Scratches head……
But they do know that co2 will warm the earth?????
There can be no runaway warming in earth from co2.
Increasing co2 will likely cause cooling because of negative feedback.
Reginald Newell, worked at MIT, NASA, IAMAP