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During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere.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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Joel Shore says:
July 24, 2010 at 6:57 am
cba says:
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.
This is essentially the same sort of argument that Willis made in this thread http://wattsupwiththat.com/2010/03/16/another-look-at-climate-sensitivity/ and it is wrong for the same reason that his argument was wrong: If you consider all radiative effects to be forcings and none to be feedbacks then you will necessarily derive the sensitivity in the absence of feedbacks. (The reason that your value differs somewhat from the sensitivity of 0.29 deg C rise per W/m^2 I think has to do with the fact that you are computing it over such a larger range of forcing…but there may be other reasons too.)
joel, it’s an effect. My sensitivity is deg C per W/m^2, not the BS garbage of the ipcc as they try to confuse the issue. Once that sensitivity is established, then one can analyze what forcing in w/m^2 is going to have an effect and then one can apply that increase in T (plus more) to determine the amount of feedback.
Net result, there’s 0.22 K per w/m^2 that has occurred over the 33K rise due to ghgs and atmospheric effects caused by 150 w/m^2. This is an average – but it’s the real thing. Apply that to a forcing and 3.7×0.22 = 0.8 deg C rise for co2 doubling without feedbacks.
What is being claimed is that the main feedback is h2o gas and that is going to raise the temperature further. Easiest way to get a handle on this is to assume an effect and then see if it is plausible. Let’s assume the final value is 2 deg C warming. That corresponds to a 13% increase in h2o vapor if one holds relative humidity fixed – a common climate assumption. What forcing or power absorption does 13% h2o vapor provide?
Essentially, at the tropopause, one has 3.7w/m^2 for a co2 doubling and 2.7 w/m^2 for a co2 doubling at 120km. If one includes the 13% h2o as well, one winds up with 5.1 w/m^2 and 4.1 w/m^2 respectively. Applying the sensitivity, that gives 5.1×0.22 = 1.1 deg C rise, scarcely half of the power increase necessary to achieve the 2 deg C that the new concentration of h2o vapor is based upon. In fact, not even a 30% rise in h2o vapor content is going to result in a 2 deg C rise and that 30% increase requires a full 5 deg C rise in temperature.
The other interesting factor is that 0.22 deg C / W/m^2 is lower than the straight radiative solution. That means on the real Earth, there is a net negative feedback present. Of course what we know is that clouds form when more h2o vapor is present and there is such a thing as convection (not to forget the h2o cycle as well).
It’s robust and self consistent. It doesn’t require invoking magical mystery tipping points etc. And, the ultimate elegance is that it makes use of real world values. There is an average of 150 w/m^2 blocking present because the Earth gets around 240 w/m^2 from the sun and the mean surface T is about 288k and the emissions are about 390w/m^2. The Earth is at 288k and it would be at 255k given the same radiation being absorbed as present. 33/150 = 0.22 is b real world stuff.
How do clear sky models, downwelling LW radiation, etc., explain this?
Or this?
Or this?
Or this?
Or this?
Radiation propagates at the speed of light. Molecular collisions exchange heat on picosecond time scales. Yet the charts above show changes on multi-decadal scales [and I have about 50 more charts showing the same thing].
Will someone please explain how back LW radiation operates for many years on, then many years off? Because to an unbiased observer, these charts contradict the conjecture of a near instantaneous CO2 effect on temperature.
anna v says:
July 27, 2010 at 5:20 am
John Finn says:
July 27, 2010 at 3:31 am
You are out of your depth in this, do not swim any further.
http://en.wikipedia.org/wiki/Greenhouse_effect
The greenhouse effect is a process by which radiative energy leaving a planetary surface is absorbed by some atmospheric gases, called greenhouse gases. They transfer this energy to other components of the atmosphere, and it is re-radiated in all directions, including back down towards the surface. This transfers energy to the surface and lower atmosphere, so the temperature there is higher than it would be if direct heating by solar radiation were the only warming mechanism
and this is Peden’s oven
Anna
Solar energy is a key part of the equation. There is an energy source. Roy Spencer recently had the same problem (as I do now) convincing posters of this same point.
You could though try explaining how, since we only get an average of ~235 w/m2 from the sun, the earth’s average temperature is ~288K.
—————-
kwik,
Good idea to read through all the posts again.
I will do it, but . . . . . to assimilate it or to be assimilated by it? That is the question
Here goes, back to comment #1 and reading . . . . . . .
John
Joel Shore says:
July 26, 2010 at 7:07 am
…So, you can’t just wave your hands and say “Upward energy transport”. That transport won’t do a darn thing to change the emission back out into space unless it changes the temperature structure in such a way that the emitting layers warm enough to increase the emission back up to where it balances the absorption again.
Are you familiar with the difference between dry and saturated (moist) adiabatic lapse rate?
Dry is ~ 1 K/100m, moist ~0.65 K/100m. Convection and condensation of H2O in clouds indeed do “change the temperature structure” locally, but cumulative globally over a relatively large area of the eath surface. Even when part of the H2O condensates and rains out, the remaining “elevated” air does have a higher temperature at high altitudes near cumulus and cb clouds than would be indicated by the dry lapse rate alone. And this is a primary mechanism to transport heat energy to atmospheric layers that can easily radiate it into space. They also of course increase the earth albedo.
tallbloke says:
July 27, 2010 at 3:51 am
The Earth’s surface (the bit that matters in terms of bulk energy transfer) doesn’t get a constant amount of energy from the sun. It is varying all the time due to albedo changes by much larger numbers of watts than co2 is involved with.
You are the one who hasn’t understood the problem.
Changes in albedo and other cooling/warming mechanisms are irrelevant to the issue under discussion. But I suspect you knew that.
John Finn says:
“You could though try explaining how, since we only get an average of ~235 w/m2 from the sun, the earth’s average temperature is ~288K.”
John, you have got to know there is something wrong with that sentence. Hint:
“You could though try explaining how, since we only get an average of oranges, the earth’s apples are ~288K.”
We do not know enough about all the different factors influencing the planet’s temperature at any one point in time to equate Watts per M^2; with an exact temperature. That assumed temperature comes straight from a model.
Yes, Solar energy is a key part of the equation. But what is the exact equation?
Answer: we don’t know. Changes in clouds and albedo figure into it, but they are not quantified. How do you quantify 3 million undersea volcanoes? And of course there may be unknown unknowns in operation.
What we do know is that the presumed effect of CO2 isn’t doing what it is claimed to do. The temperature rises and falls over decades, centuries and millennia, despite a smooth rise in a minor trace gas.
When the models and the data do not agree, the models are wrong.
John Finn says:
July 27, 2010 at 12:53 pm
Changes in albedo and other cooling/warming mechanisms are irrelevant to the issue under discussion. But I suspect you knew that.
The issue under discussion is the misconceptions on “the greenhouse effct”. One of the major misconceptions of which is that you can assume all other effects are feedbacks, apart from co2 which is the one true climate forcing, because, you claim, solar is ‘constant’.
I’m not going to let you shuffle the pea und under the cups like that John, and I know you know better. The important aspect of solar, the actual insolation at the ocean surface, is not constant, and varies by large amounts more than the alleged co2 forcing according to the empirical data. Childhoods end mate, we are not up for being bul[snipp]ed any more.
So if you are going to insist that it’s not part of the discussion, you have written yourself out of the discussion.
Thanks for playing.
Hmmm, apologies for getting annoyed. I just hate it when people unjustifiably limit the debate.
tallbloke says:
July 27, 2010 at 2:29 pm
Hmmm, apologies for getting annoyed. I just hate it when people unjustifiably limit the debate.
Perhaps I ought to explain what I meant by “the discussion”. This referred to the specific exchange with Anna V who I believe is incorrect rather than the general topic of discussuion.
cba says:
July 27, 2010 at 9:57 am
Net result, there’s 0.22 K per w/m^2 that has occurred over the 33K rise due to ghgs and atmospheric effects caused by 150 w/m^2. This is an average – but it’s the real thing. Apply that to a forcing and 3.7×0.22 = 0.8 deg C rise for co2 doubling without feedbacks.
To increase outgoing radiation at TOA by 4 w/m2, the surface will need to radiate more than another 4 w/m2. Only around 60% of the surface increase will eventually escape to space. The surface will need to radiate an extra ~6.6 w/m2 which will require a temp increase of ~1.2 deg.
Joel Shore (July 26, 2010 at 1:48 pm):
Thanks for taking the time to reply.
Ambiguity of reference by the word “heat” is not the only source of non-falsifiability for climatology. Another is the failure of the IPCC climate models to make predictions. According to the IPCC itself, these models make “projections” ( see http://icecap.us/images/uploads/SPINNING_THE_CLIMATE08.pdf ).
A “projection” is a mathematical function that maps the time to the computed global average temperature anomaly. A “prediction” is a proposition that states the outcome of a statistical event or events; the complete set of these events form the statistical population for the testing of the associated model.
Laymen, including journalists and political figures, are prone to confusing projections with predictions. Thus, they are prone to thinking there is a scientific basis for the IPCC’s conclusion of anthropogenic global warming when there is none. Rather than being based upon science, the IPCC’s conclusion is based upon an appeal to illegitimate authoriy.
Cordially, Terry Oldberg
KLA says:
Yes. I am very familiar with it. Perhaps you missed this post http://wattsupwiththat.com/2010/07/23/quantifying-the-greenhouse-effect/#comment-439141 where I noted the negative feedback known as the lapse rate feedback that arises (at least in large part) because of the fact that the vertical temperature structure in the tropics on average closely follows the moist adiabatic lapse rate. My point is not that Stephen Wilde’s notion of an increase in the hydrological cycle and associated effects is completely wrong; my point is that to the extent it is correct, it is already understood and accounted for in all the climate models.
Terry,
Thanks for your response. Your discussion of prediction vs projection is another red herring. The reason that the IPCC makes projections is that it doesn’t try to predict what the future course of our societies will be but instead comes up with plausible scenarios and then predicts the resulting warming for each scenario. It is just a way of basically saying, “The future is in our hands, but if we do X then we can expect Y to happen.”
It would be tragic if the last comment on this blog were Joel Shore’s.
The IPCC has clearly failed humanity and any attempt to question otherwise is foolish! The “Science” is NOT settled unless you are a politician!
Joel Shore (July 27, 2010 at 4:51 pm):
Thanks for taking the time to reply.
According to Merriam-Webster, a “red herring” is “something that distracts attention from the real issue.” In accusing me of employing a “red herring,” you’ve responded to my argument with an ad hominem argument. An “ad hominem argument” is one that attacks the person making this argument as unworthy of belief in view of this person’s character flaws rather than attacking this person’s argument. Often, unprincipled debaters employ ad hominem arguments when grounds for attacking the victim’s argument are lacking. However, an ad hominem argument is illogical because it is irrelevant.
Here, the argument under debate is my argument that the IPCC models are not empirically falsifiable. If they were empirically falsifiable, you would be able to identify the statistical population by which these models could be falsified. If they were not empirically falsifiable, you would not be able to do so. In the citation which I supplied to you, the IPCC expert reviewer Vincent Gray testifies, in effect, that there is no statistical population.
The IPCC’s grounds for making projections are irrelevant to the issue of whether my argument is correct. If my argument is correct, the IPCC lacks a scientific basis for its conclusion of anthropogenic global warming. In responding to my argument with an ad hominem argument rather than addressing my argument, you seem to have conceded that a scientific basis is in fact lacking.
Cordially, Terry Oldberg
RE: Jim D 6:35pm July 26th and responses.
I posted a mainstream paper, not a controversial one at all. Nobody on any blogs or in any other papers criticized it. It is built on observations and line-by-line radiation models that are themselves based on our quantum mechanical understanding of molecules and detailed lab verification. To deny this paper is to deny quantum mechanics, and the whole field of atomic science from which these models come. Yes, CO2 effects are easiest to measure in the Antarctic due to the dryness, so that is a good place to see them. You could also make such measurements of downward IR spectra at 10 km altitude over the US where it is equally dry, but harder to get long-term continuous measurements. CO2 effects are easily measurable, and that is the point I was making.
John Finn says:
July 27, 2010 at 3:43 pm
cba says:
July 27, 2010 at 9:57 am
Net result, there’s 0.22 K per w/m^2 that has occurred over the 33K rise due to ghgs and atmospheric effects caused by 150 w/m^2. This is an average – but it’s the real thing. Apply that to a forcing and 3.7×0.22 = 0.8 deg C rise for co2 doubling without feedbacks.
To increase outgoing radiation at TOA by 4 w/m2, the surface will need to radiate more than another 4 w/m2. Only around 60% of the surface increase will eventually escape to space. The surface will need to radiate an extra ~6.6 w/m2 which will require a temp increase of ~1.2 deg.
==================================
that is a clear sky only, radiative solution only. The number I’m showing is actually what is going on average for all of the ghg/cloud effects on Earth under conditions one sees today. The fact that it is 0.22 deg C rise per W/m^2 rather than 0.29 deg C rise per W/m^2 is because there is net negative feedback involved.
On the science side, and I am glad David Springer read the whole paper, two points. They found that the ratio of the CO2 to H2O effect did not change with season when H2O changed by a factor of two. They explained this in terms of the emission lines of CO2 becoming more distinct from H2O as the background temperature changes and the spectrum shifts with temperature towards the CO2 emission peak, so no mystery there, and actually some quite neat science. Emission lines of course are related to absorption lines, so you expect CO2 emission at 15 microns if it absorbs there, to answer the other doubt.
899 raises an issue about upwards and downwards fluxes. As far as the ground is concerned, the downward flux is enhanced by GHGs, warming it more than it would have without GHGs. Once the ground gets warmer it can also radiatively heat the air with upward flux, but convection is more dominant in warming the air than radiation.
Jim D says:
“CO2 effects are easily measurable, and that is the point I was making.”
Jim, if that is true then you have completely solved the previously unsolved question of what the climate sensitivity number for CO2 actually is. The IPCC says 3°C – 6°C. I look forward to your paper setting them straight [and they need to be set straight].
Congratulations! With your solution you’re on the short list for the [now worthless] Nobel Prize. But first, you had better tell the climate modelers:
http://img254.imageshack.us/img254/2626/tempobsrvvsco2ct4.png
#
Jim D says:
July 27, 2010 at 6:57 pm
On the science side, and I am glad David Springer read the whole paper, two points. They found that the ratio of the CO2 to H2O effect did not change with season when H2O changed by a factor of two. They explained this in terms of the emission lines of CO2 becoming more distinct from H2O as the background temperature changes and the spectrum shifts with temperature towards the CO2 emission peak, so no mystery there, and actually some quite neat science. Emission lines of course are related to absorption lines, so you expect CO2 emission at 15 microns if it absorbs there, to answer the other doubt.
899 raises an issue about upwards and downwards fluxes. As far as the ground is concerned, the downward flux is enhanced by GHGs, warming it more than it would have without GHGs. Once the ground gets warmer it can also radiatively heat the air with upward flux, but convection is more dominant in warming the air than radiation.
#
=====================
Jim,
not only co2 but also h2o vapor is a log function when it comes to blocking IR. Doubling h2o is just an incremental effect, one of several doublings. The h2o doubling has about twice the effect of a co2 doubling in W/m^2. It’s no wonder that you don’t see a tremendous change in absorption/emission with a factor of two change in h2o vapor. It seems that people forget this all too often.
Smokey, some people here were questioning whether CO2 effects can even be seen or measured, which was amazing to me. I answered that with a paper showing clear observations. Sensitivity of global climate to CO2 doubling is a whole different issue from point measurements that show CO2 does anything.
cba, normally you would expect to see the ratio change if one of components, CO2 or H2O, doubled without the other. It was interesting that it didn’t, but also explainable with known physics. A lot of people here don’t believe in basic physics, let alone climatology, so let’s get the physics straight first, otherwise it really is hopeless.
Pardon the rant but,
I always believed you can’t fully follow, and objectively take sides, on the GHG science without the basic building blocks in physics, and I think this thread is proving people don’t have those building blocks yet, and next thing you know, we’ll be trying to defend quantum mechanics. What is the lowest common denominator? Do people believe in quantum mechanics? If so, how about atomic and molecular physics and interaction with radiation? How about absorption and emission lines, and the Planck function? How about specifically the molecular radiation properties of various gases from theory and verification in the lab? How about atmospheric measurements of these things that are explainable in terms of the above listed? How about the fact that those measurements include what we call back radiation? Then, on to the original post which only builds on this physics, and you are only a few more steps from understanding GHG theory, but instead of debating those steps, we are stuck at steps one and two.
Joel Shore says:
July 27, 2010 at 4:51 pm
The reason that the IPCC makes projections is that it doesn’t try to predict what the future course of our societies will be but instead comes up with plausible scenarios and then predicts the resulting warming for each scenario. It is just a way of basically saying, “The future is in our hands, but if we do X then we can expect Y to happen.”
I think you are wrong Joel. Each scenario is a projection. It is not a rigorous output with correct error propagation and display of that error for each scenario. So the resulting warming from each scenario is a projection also , not a prediction.
John Finn :
July 27, 2010 at 11:55 am
I do not disagree that the earth is warmer than it would be without an atmosphere and certainly warmer than it would be without the magical H20 and the marginal CO2.
That the main heat source is the sun is also a given.
I specifically disagree in the mishmash of classical thermodynamics and quantum statistical mechanics that is hand waving back radiation etc.
If I were computing the temperature of the earth I would use a specifically written Stefan formula probably treating the skin surface (ground) temperature as body1 and layering the atmosphere in spherical rings with their heat capacity etc. I took thermodynamics 301 back in 1960 and am too rusty to lift up my sleeves and calculate and the last program I wrote was back in 2000. I can judge though if a calculation is internally consistent or not. Mixing up thermodynamics and quantum statistical mechanics is not a consistent way of calculating and leads to paradoxes, as Peden’s oven.
Jim D says:
July 27, 2010 at 8:18 pm
Do people believe in quantum mechanics? If so, how about atomic and molecular physics and interaction with radiation? How about absorption and emission lines, and the Planck function? How about specifically the molecular radiation properties of various gases from theory and verification in the lab? How about atmospheric measurements of these things that are explainable in terms of the above listed? How about the fact that those measurements include what we call back radiation?
Physics is not a matter of beliefs. It is an elegant system that has developed many frameworks that describe matter and energy, starting from axiomatic statements ( i.e. not provable but accepted as a premis) and ending in predictions in numbers to be compared with the data.
If the predictions are wrong one goes back to the premises and modifies them and comes back to new predictions. It is the scientific method and has nothing to do with beliefs.
Do you believe in a chess game? Or are you accepting its premises, playing consistently according to the rules and accept the outcome? You do not introduce the rules of a different game when playing chess.
There is nothing conceptually wrong with looking at the quantum mechanical formulation of radiation in the atmosphere. The error comes when, because it is extremely cumbersome and difficult to calculate what happens using quantum statistical ensembles, which is the rigorous way if one is using the quantum framework, one starts introducing a different framework, thermodynamic calculations, by taste and ad hoc.
Mixing frameworks in calculations leads to paradoxes like violating the second thermodynamic theorem and Peden’s oven.
When people understand this they can say they understand physics. Unfortunately, climatologists have been using physics as a tool box and not checking for consistencies.