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During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere.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.
Jim G says:
July 23, 2010 at 2:05 pm
stephen richards says:
July 23, 2010 at 12:15 pm
R. Gates says:
“Another of your cracked replies courtesy of the Gavin Schidt school of answers.”
“Gravity does not generate energy. Energy cannot be made or destroyed einstein.
Sure, gravity is a force which creates the conditions for the creation of stars and the nuclear energy in those stars is started by the force of gravity compressing the gases.”
__________________
So, you said I was wrong and then said I was right. My point was in reply to someone who was confused about CO2 “generating” energy. Gravity is the reason we have stars and galaxies, along with of course, this mysterious thing called dark matter and dark energy. Gravity is the reason that entropy can be overcome on a local (i.e. galaxy and star level). Gravity allows stars to gather enough mass to ignite and then they emit energy that allows entropy to be overcome on a very local level. So, gravity is the ultimate source of energy for we humans and other creatures to overcome entropy on a very local level, for we know that on a universal level, 99.9% or more of the universe is already in a state of heat death, having reached maximum entropy. So thank gravity everytime you feel the sun on your face and are able to overcome entropy, if only for a while…
tallbloke, Stephen Wilde,
As far as the ocean is concerned it absorbs 92% of the solar flux and 99% of the longwave (back radiation) flux. It doesn’t care if it is solar or longwave (IR) – a Watt per square meter is a Watt per square meter. You can’t choose one input and ignore the other. On the outgoing side are surface-emitted longwave flux, heat flux, and latent heat flux. You can’t say evaporation is just responding to longwave flux – these are just two of the five budget terms listed above.
Once you admit longwave flux is important, you need to consider GHGs including CO2 which provide it (in addition to clouds).
tallbloke:
I’m best on concepts and logic. Can’t do the numbers unfortunately.
Actually no one has got the right numbers yet as I’ve repeatedly told Leif and Bob.
Go to it 🙂
My take from the above post by Ben Herman and Roger A. Pielke Sr is as the follows:
Based on this understanding of their post, if “delay the cooling of the total earth system” is the operative GHG effect (GHGE) due to change in CO2 concentration, then the time factor is dominant since the “delay of cooling” is a quantity with units of delta T/time/time and the increase in CO2 concentration is a quantity with the units of delta concentration/time. It appears to me that therefore, it is the rate of change of the rate of change of T that is caused by the rate of change of CO2 concentration.
?Can this be, or do I have it backwards?
Comments please!
John
899 writes:
“THIMK: If the Earth is first heated by energy released from a gas molecule, and then the Earth releases that energy to a gas molecule, then how does the gas molecule ‘reheat’ the Earth?”
I am thimking. I am looking at the radiation as a cause. So, if absorption of radiation increases temperature in the body that absorbs it, radiation from a CO2 molecule will increase temperature. What is wrong with that claim? Earth does not care where the radiation came from, so to speak, it just gets warmer.
On your view, I should thimk that because Earth lost radiation that is now returning because of CO2 molecule banditry, then the addition of the two equals zero. I have no problem with that, but to say that the returning radiation does not warm the Earth is to deny causality to that one emission of radiation.
As a separate point, radiation coming from CO2 could be treated mathematically as if it came from the sun. Under that mathematical treatment, warming from CO2 would have to be responsive to changes in radiation from the sun? Why not view CO2 as a magnifying glass between Sun and Earth?
wws says:
July 23, 2010 at 12:38 pm
R. Gates wrote: “Ultimately of course, the source of all energy in our region of the universe is gravity,”
You must have missed being taught that “It’s better to keep quiet and be thought a fool than to open your mouth and prove it beyond all doubt.”
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Have you really thought about this? I’m doubting it, or perhaps you are the topic of your own oft quoted saying. The fact is that that gravity is the reason we have useful energy in this part of universe. I never said gravity is energy or any such thing as that, but gravity allows entropy to be overcome on a local basis. Everytime you’re able to sort your white socks from your black socks, or enjoy a tasty turkey sandwich, you can thank gravity as the ultimate reason you have that energy to overcome entropy, if only for a while.
BTW, if you think of another ultimate reason (that doesn’t related back to gravity) that we can overcome entropy in this very localized region of the universe, please let me know.
Barry Moore,
Some opacity of co2 peaks occurs in as little as a few cm. Off peak values stretch out path length dramatically. These molecular interactions between like and dissimilar molecules are maintaining the local temperature between co2, h2o and the other molecules present and there will be absorption and emissions based upon the temperature. Excitation will be a combination of photon captures and thermal collisions and de-excitation results from thermal collisions and photon emissions. As one goes up in the atmosphere, pressure drops and the pressure broadening decreases, making capture less likely in the wings.
net result is that co2 does have some effect. see my first post in this thread for more details.
Jim D says:
July 24, 2010 at 8:42 am (Edit)
tallbloke, Stephen Wilde,
As far as the ocean is concerned it absorbs 92% of the solar flux and 99% of the longwave (back radiation) flux. It doesn’t care if it is solar or longwave (IR) – a Watt per square meter is a Watt per square meter.
I’m not sure which part of ‘solar shortwave penetrates the ocean tens of meters’ and ‘longwave radiation from the greenhouse can’t penetrate the ocean much beyond it’s own wavelength’ you don’t understand. How can I make it plainer for you?
The Sun’s energy goes right into the ocean, where it can stay for years. The downwelling GHG flux can only concentrate right on the surface, where all those watts/m^2 cause a rapid and radical temperature increase, which is absorbed in the latent heat of evaporation.
The warmists will bluster about this, saying the heat gets in there this or that way. Ask them to show you the data. In fact, I’ll ask you.
Show me the data.
Jim D
I think you will find that the response of water to longwave as opposed to shortwave is very different.
The thing is that longwave IR never gets past the region involved in the evaporative process whereas shorter wavelengths do.
In order to affect ocean heat content a wavelength must get past the evaporative barrier.
Back radiated IR from CO2 just doesn’t.
Theo Goodwin says:
July 24, 2010 at 8:51 am (Edit)
I am looking at the radiation as a cause. So, if absorption of radiation increases temperature in the body that absorbs it, radiation from a CO2 molecule will increase temperature. What is wrong with that claim? Earth does not care where the radiation came from, so to speak, it just gets warmer.
Yes, but Earth got cooler by radiating into the atmosphere in the first place. That the point 899 is trying to make I think. So the fact that moastly water vapour and a little bit of co2 send half back again before finally failing to catch the ball and letting it out into space is neither here nor there, except indsofar as the number of times they do catch it and bounce it back to Earth slows down the cooling rate.
jae says:
July 24, 2010 at 8:00 am
“(4) But that cannot happen because of the Second Law; the cooler atmosphere cannot contribute heat to the warmer surface.”
Why do your clothes keep you warm on a winter day? Are they not at a lower temperature than you are?
Jim G says:
July 23, 2010 at 2:05 pm
“As several of us discussed in a previous post, gravity is not even really a force but a condition, curvature, of space-time which occurs in the presence of mass causing everthing in its reach to move in a straight line though curved space. The source of energy represented by radioactive material in otherwise empty space would not be due to present gravity though it was originally created by gravity…”
______________
I think you are confused about things a bit. Exactly what gravity is, no one really knows. Is it merely a curvature of spacetime, or is an actual force that is transmitted by a particle called the “graviton”? No one knows…
http://scienceworld.wolfram.com/physics/Graviton.html
The point isn’t really that we have to know what it is, but simply what it does. What is does is allows entropy to be overcome on a (universally speaking) local level. We have sunshine because of gravity. That sunshine travels to the earth and warms it. GHG’s trap enough of that sunshine to maintain the earth at an nice range where surface life can thrive. Life trives by using energy to overcome entropy during the lifetime of the organism.
Stephen Wilde says:
July 24, 2010 at 8:44 am (Edit)
tallbloke:
I’m best on concepts and logic. Can’t do the numbers unfortunately.
Actually no one has got the right numbers yet as I’ve repeatedly told Leif and Bob.
Go to it 🙂
Sure, I’ll just whip out my pocket radiometer and nip out into the garden. Back in ten. 🙂
In answer to John Whitman
July 24, 2010 at 8:47 am
The original post did not say anything about delaying the cooling, as it talks about equilibrium states. There is a fixed heating rate and a cooling rate that adjusts to that in such a way as to balance it, leading to equilibrium. The adjustment is through temperature which rises till the cooling rate equals the heating rate. CO2 puts a spanner in the cooling-rate works that means the surface has to go to a higher temperature to balance the same heating rate. Think of it as a resistance to the cooling efficiency.
jae says:
July 24, 2010 at 8:00 am
I’m still puzzled:
(1) The heat of an object is a function of the total amount of thermal radiation directed upon it.
(2) During the day, when the sun is shining, the surface of, say, a piece of asphalt is heated by the sun to a temperature that is higher than the air temperature.
(3) The standard GHG theory says that there is backradiation, which affects the temperature of the atmosphere (preventing it from cooling off as fast as it would without GHGs). This backradiation would have to be ADDED to the solar radiation during daytime to determine the total energy being received by the asphalt. That would HAVE to lead to an even higher temperature than produced by the sun alone (see (1) above).
(4) But that cannot happen because of the Second Law; the cooler atmosphere cannot contribute heat to the warmer surface.
(5) Therefore, something’s wrong with the “GHG hypothesis” as explained in this post.
Can someone explain where I am wrong?
Yes you are mistaken about the 2nd, as you’ve stated it it doesn’t apply to radiation, for which net heat flow is the key.
Consider your black asphalt surface receiving 1000W/m^2 from the sun and about 350W/m^2 of downwelling IR therefore it will heat up to a temperature that will radiate 1350W/m^2. Net heat flow is 650W/m^2 from the surface to the cooler atmosphere but there is always flow in both directions.
tallbloke: You wrote, “Therefore we need to consider the cumulative total of solar energy input not just it’s instantanous level.”
The impacts of ENSO events on tropical and extratropical cloud amount need to be considered, also, as these can cause signifcant changes in DSR.
Jim G said:
“GHG’s trap enough of that sunshine to maintain the earth at an nice range where surface life can thrive.”
Just a thought, Jim. How much is ‘trapped’ by those pesky GHGs and how much is ‘trapped’ by our oceans.
You may conclude that not only is the anthropogenic portion of CO2 in the air insignificant in relation to the natural CO2 in the air but that the CO2 in the air is insignificant in relation to what the H2O in the air is doing or even that the air in it’s entirety is utterly insignificant in relation to what the oceans are doing.
Isn’t the issue of anthropogenic CO2 just plain silly ?
Are you a member of the ‘tail wags dog’ community ?
tallbloke, Stephen Wilde,
I see where we differ. You think that downward longwave flux has no influence at all on ocean temperature in the long term. I don’t agree at all with that view. By keeping the top of the ocean from cooling towards 255 K (as it would with just mean solar radiation), it maintains the thermal profile in the ocean, preventing convective mixing that would otherwise bring the colder water down and reduce the ocean heat content.
Spector says:
July 24, 2010 at 8:34 am
The results from one online absorption effect calculation tool based on MODTRAN data suggests that there may be an additional temperature effect proportional to the seventh power of the log of the CO2 concentration that would kick in around 7200 ppm, but I have not seen any explanation of why this might be the case.
Based on the theory you’d expect a transition from log(CO2) to sqrt(CO2) at higher concentration.
Having recently been made aware of my ignorance re: certain components of this complex topic(namely the Weinstein Displacement Law- as yet an unresolved condition) I find the current submission an embarrassment, intended, as it presumes, to inform to the above, often learned, commentary.
Jim D says:
July 24, 2010 at 9:24 am
In answer to John Whitman
July 24, 2010 at 8:47 am
The original post did not say anything about delaying the cooling, as it talks about equilibrium states. There is a fixed heating rate and a cooling rate that adjusts to that in such a way as to balance it, leading to equilibrium. The adjustment is through temperature which rises till the cooling rate equals the heating rate. CO2 puts a spanner in the cooling-rate works that means the surface has to go to a higher temperature to balance the same heating rate. Think of it as a resistance to the cooling efficiency.
——————————
Jim D,
Here is a whole paragraph from “Explaining misconceptions on ‘The Greenhouse Effect'” by Ben Herman and Roger A. Pielke Sr. I took the whole paragraph to minimize the possibility that I am quoting them out of context.
So, it appears to me they are saying “loss of energy” which I translated to cooling.
Another paragraph from the post here:
Bob Tisdale says:
July 24, 2010 at 9:37 am (Edit)
The impacts of ENSO events on tropical and extratropical cloud amount need to be considered, also, as these can cause signifcant changes in DSR.
Yes, I agree. This is why the SST can run counter to the sunspot area cumulative total on my chart, for periods as long as the phase of the PDO. It does seem to even out to the solar values over ~60 years though.
Jim D said:
“There is a fixed heating rate and a cooling rate that adjusts to that in such a way as to balance it, leading to equilibrium.”
Now Jim, nothing in nature is fixed.
The rate of energy release from the oceans to the air varies depending on internal ocean cycles.
The rate of energy release from atmosphere to space varies with the level of solar surface activity.
The composition of the Earth’s atmosphere varies over time.
The net energy output of the sun varies over time.
The speed of the hydrological cycle varies to offset any variable other than:
i) Total atmospheric density (and thus pressure at the surface)
ii)The properties of the phase changes of water
Thus is equilibrium maintained over billions of years.
The issue has been resolved 🙂
Jim D says:
July 24, 2010 at 9:37 am (Edit)
tallbloke, Stephen Wilde,
I see where we differ. You think that downward longwave flux has no influence at all on ocean temperature in the long term. I don’t agree at all with that view. By keeping the top of the ocean from cooling towards 255 K (as it would with just mean solar radiation), it maintains the thermal profile in the ocean, preventing convective mixing that would otherwise bring the colder water down and reduce the ocean heat content.
So you now agree radiation from GHG’s affect the rate of cooling, rather than actively heating the ocean by penetrating it and emitting photons into water molecules then?
Jim D,
Sorry, I screwed up those pesky blockquote html editing commant in the last two sentences in my previous comment to you.
John
[reply] try using italics tags instead. RT-mod