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Is the CO2 effect saturated?

What the science says...

Select a level... Basic Intermediate Advanced

The notion that the CO2 effect is 'saturated' is based on a misunderstanding of how the greenhouse effect works.

Climate Myth...

CO2 effect is saturated

"Each unit of CO2 you put into the atmosphere has less and less of a warming impact. Once the atmosphere reaches a saturation point, additional input of CO2 will not really have any major impact. It's like putting insulation in your attic. They give a recommended amount and after that you can stack the insulation up to the roof and it's going to have no impact." (Marc Morano, as quoted by Steve Eliot)

The mistaken idea that the Greenhouse Effect is 'saturated', that adding more CO2 will have virtually no effect, is based on a simple misunderstanding of how the Greenhouse Effect works.

The myth goes something like this:

  • CO2 absorbs nearly all the Infrared (heat) radiation leaving the Earth's surface that it can absorb. True!
  • Therefore adding more CO2 won't absorb much more IR radiation at the surface. True!
  • Therefore adding more CO2 can't cause more warming. FALSE!!!

Here's why; it ignores the very simplest arithmetic.

If the air is only absorbing heat from the surface then the air should just keep getting hotter and hotter. By now the Earth should be a cinder from all that absorbed heat. But not too surprisingly, it isn't! What are we missing?

The air doesn't just absorb heat, it also loses it as well! The atmosphere isn't just absorbing IR Radiation (heat) from the surface. It is also radiating IR Radiation (heat) to Space. If these two heat flows are in balance, the atmosphere doesn't warm or cool - it stays the same.

Lets think about a simple analogy:

We have a water tank. A pump is adding water to the tank at, perhaps, 100 litres per minute. And an outlet pipe is letting water drain out of the tank at 100 litres per minute. What is happening to the water level in the tank? It is remaining steady because the flows into and out of the tank are the same. In our analogy the pump adding water is the absorption of heat by the atmosphere; the water flowing from the outlet pipe is the heat being radiated out to space. And the volume of water inside the tank is the amount of heat in the atmosphere.

What might we do to increase the water level in the tank?

We might increase the speed of the pump that is adding water to the tank. That would raise the water level. But if the pump is already running at nearly its top speed, I can't add water any faster. That would fit the 'It's Saturated' claim: the pump can't run much faster just as the atmosphere can't absorb the Sun's heat any faster

But what if we restricted the outlet, so that it was harder for water to get out of the tank? The same amount of water is flowing in but less is flowing out. So the water level in the tank will rise. We can change the water level in our tank without changing how much water is flowing in, by changing how much water is flowing out.

water tank

Similarly we can change how much heat there is in the atmosphere by restricting how much heat leaves the atmosphere rather than by increasing how much is being absorbed by the atmosphere.

This is how the Greenhouse Effect works. The Greenhouse gases such as carbon dioxide and water vapour absorb most of the heat radiation leaving the Earth's surface. Then their concentration determines how much heat escapes from the top of the atmosphere to space. It is the change in what happens at the top of the atmosphere that matters, not what happens down here near the surface.

So how does changing the concentration of a Greenhouse gas change how much heat escapes from the upper atmosphere? As we climb higher in the atmosphere the air gets thinner. There is less of all gases, including the greenhouse gases. Eventually the air becomes thin enough that any heat radiated by the air can escape all the way to Space. How much heat escapes to space from this altitude then depends on how cold the air is at that height. The colder the air, the less heat it radiates.

atmosphere
(OK, I'm Australian so this image appeals to me)

So if we add more greenhouse gases the air needs to be thinner before heat radiation is able to escape to space. So this can only happen higher in the atmosphere. Where it is colder. So the amount of heat escaping is reduced.

By adding greenhouse gases, we force the radiation to space to come from higher, colder air, reducing the flow of radiation to space. And there is still a lot of scope for more greenhouse gases to push 'the action' higher and higher, into colder and colder air, restricting the rate of radiation to space even further.

The Greenhouse Effect isn't even remotely Saturated. Myth Busted!

Basic rebuttal written by dana1981


Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

 

Last updated on 7 July 2015 by pattimer. View Archives

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Further reading

V. Ramanthan has written a comprehensive article Trace-Gas Greenhouse Effect and Global Warming.

Comments

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Comments 126 to 150 out of 663:

  1. KR (RE: 125), "As has been said to you before, the windowing effect (where IR goes straight from the surface to space) is only part of the reduction in IR. The rest occurs in the full absorption bands (where IR from the surface makes it only 10's or 100's of meters before absorption)" When I refer to the "window", I mean transmittance - the amount of the whole spectrum of emitted surface power that passes through to space without being absorbed by the atmosphere (not just one particular band). This is the amount that should reduce by 7.4 W/m^2 if the referenced 3.7 W/m^2 is all incident on the surface as claimed when CO2 is doubled. There appears to be some confusion in regards to the definition or use of the term "window". Some refer to this as the mostly transparent region between about 8u and 13u, but this is not how I use the term. Nor do I believe this is how 'novandilcosid' is using the term either. You don't seem to understand that there are other parts of the spectrum besides the CO2 absorbing bands that are not completely saturated and a portion of surface emitted energy passes through them unabsorbed out to space. The aggregate amount that passes through the whole spectrum of emitted surface energy is the "window" or transmittance.
  2. KR (RE: 125), Trenberth et al 2009 has a transmittance or "window" of 70 W/m^2 (40 through the clear sky and 30 through the clouds). If when CO2 is doubled, the "window" decreases by 3.7 W/m^2 (or 7.4 W/m^2) and 1.85 goes up out to space and 1.85 goes down to the surface (or 3.7 goes up and 3.7 goes down) (*Trenberth actually has it being 52% up and 48% down).
  3. RW1 - Got it, you are going to continue to disregard the spectra between 600-750 microns, let alone around 450 microns, where IR from the surface cannot reach space unintercepted, and where increasing CO2 concentrations raise the effective emission to space to higher/colder altitudes. Quite frankly, I cannot take your discussion of the greenhouse effect seriously when you ignore major components like this.
  4. KR (RE: 128), I'm not disregarding any spectra. I'm also well aware there are bands that are saturated. I also agree that the CO2 absorbing bands are not saturated - there is room on the wings to expand and capture a little more outgoing surface power. This is where the additional 3.7 W/m^2 from 2xCO2 is coming from.
  5. RW1 @127, I don't want to buy into another fruitless conversation but, Trenberth 09 shows a 40 Watt/m^2 atmospheric window, and also shows 30 W/m^2 emitted to space from cloud surfaces, with another 169 W/m^2 emitted from the atmosphere other than from clouds. These three combine to make up the OLR.
  6. Tom Curtis (RE: 130), "RW1 @127, I don't want to buy into another fruitless conversation but, Trenberth 09 shows a 40 Watt/m^2 atmospheric window, and also shows 30 W/m^2 emitted to space from cloud surfaces, with another 169 W/m^2 emitted from the atmosphere other than from clouds. These three combine to make up the OLR." I don't see how this is possible. Think about it. How can the clear sky atmosphere emit 169 W/m^2 to space when surface only emits about 131 W/m^2 to the clear sky in the first place? We know this because the ISCCP data says clouds cover 2/3rds of the surface, which means 1/3rd of the surface is clear sky. 396 W/m^2 x 0.33 = 131 W/m^2 emitted from the surface to the clear sky.
  7. John Cook, Moderators - Might I suggest a thread on the Trenberth diagram and energy budget? This has been repeatedly misunderstood, misquoted, and misused for more instances of mathturbation than just about any graphic I can think of. - It's not a model, contains no information whatsoever about interdependent changes of climate elements upon perturbation. - It's a four layer accounting of energy interchanges between these layers (Sun, surface, atmosphere, space). Some of these exchanges (161 insolation, the 40 W/m^2 "window" from surface to space) skip a layer, most do not. - Energy entering a level of this accounting does not retain identity/sourcing with what goes out; it's all joules, all the way down, which for example is why the atmosphere can radiate 169 W/m^2. - If somebody disagrees with a number in the Trenberth budget, they should take it up with Trenberth, who has done a clearly sourced and researched work with plenty of references to look at for each individual number. "I don't see how this is possible" is not a valid objection; it's certainly not science.
  8. Tom Curtis (RE: 130), I might also add that Trenberth's "window" of 70 W/m^2 is not referenced in the paper. It appears to just be a rough estimate or guess. He also has greater than half of the surface power absorbed by the atmosphere being emitted up out to space, which is inaccurate. To get half up and half down requires a "window" of 82 W/m^2 with his numbers (396 - 82 = 314; 314/2 = 157; 239 + 157 = 396 at the surface). Even this site's hfranzen from first the link I posted in #124 has diagram on page 19 of his paper showing a "window" of 88 W/m^2. Take a look: "Flux balance on the Earth"
    Response: [muoncounter] We've been through the half up/half down bit before. By assuming that model, your argument is turning circular. You're also veering off topic (and it's hard to do both at the same time). This thread is on CO2 absorption band saturation.
  9. muoncounter, OK. Maybe KR is right and there should be a dedicated thread to the Trenberth diagram and energy budget.
  10. #130 Tom Curtis at 11:21 AM on 26 April, 2011 Trenberth 09 shows a 40 Watt/m^2 atmospheric window That 40 W/m2 is not substantiated anywhere in the paper. It was just pulled into Fig. 1. out of thin air.
    Response:

    [DB] "It was just pulled into Fig. 1. out of thin air."

    Please substantiate, or withdraw, this allegation.

  11. Berényi - The infrared atmospheric window was derived in 1918 from the H2O spectra, first estimated (by hand) in 1928. Now the value of transmitted energy is determined as a side product of the line-by-line radiation models, to distinguish between surface radiation actually transmitting directly to space and atmospheric radiation on the edges of the window also radiating to space. Trenberth may have thought that it wasn't necessary to to spend much time on a value that has been known for >80 years. A value you could have determined with a few moments of web search, I'll note. In my opinion, your language here is skating the thin edges of the Comments Policy regarding accusations of deception.
    Response:

    [DB] Sometimes, in the course of human events, it's necessary to reinvent the wheel.

    As you note, the fact that some then find it necessary to reinvent the flat tire is revealing.

  12. 131, RW1,
    which means 1/3rd of the surface is clear sky. 396 W/m^2 x 0.33 = 131 W/m^2 emitted from the surface to the clear sky.
    I won't get into Trenberth's diagram with you again (entirely). I'll repeat that you don't understand it, you are making invalid assumptions, you don't understand enough of the underlying physics of atmospheric heat transfer, and this is all leading to gross misinterpretations. However, concerning this particular statement of yours about "1/3rd ... clear sky"... First, you can't just assume that because 1/3 of the sky is clear then that the clear sky absorbs 1/3 of the radiation. The ability to absorb long wave radiation is dramatically different between clear sky and clouds (clouds probably absorb substantially more, being made up of a powerful greenhouse gas, but I've never really seen any numbers on this). Clouds and the radiative properties of the surface are also not evenly distributed over the globe, either in space or in time. Everything else is not homogeneous. Second, you cannot ignore the non-radiative components (thermals and the release of latent heat). Third, and most importantly, you cannot ignore a major element which is not included in the diagram, which is the transfer of heat between "clear sky" and clouds. What happens when a cloud dissipates? Does the heat vanish? Is it forced to instantly radiate up to space? Does it fall to the ground with the rain? Hint: When a cloud absorbs LW radiation, it is capable of transferring that heat to the surrounding and pervading atmosphere (remember, a cloud isn't a solid object, it coexists in space with the O2/N2 of the atmosphere). So it doesn't really matter which absorbs the radiation. The atmosphere (consisting of "clear sky" and clouds) absorbs the radiation, and the two cannot be separated into distinct components re this diagram. This diagram is not a GCM. It's just a diagram intended to help communicate the earth's energy budget to the casual viewer, and nothing more. You cannot read as much into it as you are attempting. So, again: 1) You need to study more before you can comment on or interpret Trenberth's diagram. 2) Trenberth's diagram is not the topic of this thread. [This will be my last post on the subject (here), so please don't come back with an angry list of "but what about this?" questions. I'm not biting.]
  13. #136 KR at 22:44 PM on 26 April, 2011 Trenberth may have thought that it wasn't necessary to to spend much time on a value that has been known for >80 years. A value you could have determined with a few moments of web search, I'll note. Really? I thought the proper way to determine values of physical quantities is to measure them. On the other hand Trenberth simply assumes it is 40 W/m2. We can get a deeper insight into his thought process if we consider an old paper of his where the problem is elaborated on briefly. Bulletin of the American Meteorological Society, 1997 Earth's Annual Global Mean Energy Budget J. T. Kiehl & Kevin E. Trenberth "Some of the radiation leaving the atmosphere originates near the earth's surface and is transmitted relatively unimpeded through the atmosphere; this is the radiation from areas where is no cloud and that is present in the part of the spectrum known as the atmospheric window, taken here to be the wavelengths 8-12 µm (Fig. 7). The estimate of the amount leaving via the atmospheric window is somewhat ad hoc. In the clear sky case, the radiation in the window amounts to 99 W m-2 , while in the cloudy case the amount decreases to 80 W m-2, showing that there is considerable absorption and re-emission at wavelengths in the so-called window by clouds. The value assigned in Fig. 7 of 40 W m-2 is simply 38% of the clear sky case, corresponding to the observed cloudiness of about 62%. This emphasizes that very little radiation is actually transmitted directly to space as though the atmosphere were transparent". Taken here to be & somewhat ad hoc, indeed. A value of 40 W/m2 would imply a broadband thermal infrared optical depth of 2.29 (which roughly means the average photon gets absorbed 2.29 times before it escapes to space). On the other hand this value averaged over the entire surface is below 1.9, that is, total thermal radiation flux escaping from surface to space unimpeded is above 60 W/m2. Trenberth's simple calculation makes two omissions. One is the polar window (above wavelength 16 μm), covered only by weak water vapor absorption lines, so in extremely dry regions (like polar ones) a considerable amount of radiation can get through in that frequency band. The other one is clouds. As clouds are always fractal structures, cloud covered surface has a fractal dimension less than 2 (and decreasing poleward). Cloud fraction is usually determined by counting cloudy vs. clear sky grid cells (pixels). However, the finer the grid resolution is, the less the ratio of cloudy pixels will be, because fractals are just like that. It means even in areas categorized as "cloudy" some thermal IR can get through to space unimpeded. Therefore thermal IR radiation flux originating near the earth's surface and transmitted relatively unimpeded through the atmosphere is measured to be more than 40 W/m2, Trenberth's back-of-the-envelope calculation is only good as a lower bound. An error on the order of ~20 W/m2 in one of the components is a serious one if an average planetary imbalance of less than 1 W/m2 is pursued.
  14. Berényi - Very good; looking up the references. Which, I'll note, support the value in the 2009 paper. Does this mean you are withdrawing your accusation of manufactured data? There are a lot of uncertainties in the numbers Trenberth presents, as is clearly discussed in the article: amounts of convective activity, latent heat numbers from precipitation, large scale estimation of the surface radiance covering sufficient points to cover variation, etc. Others are much more certain: backradiation, insolation, and so on. Taken together, they add up to 10's of watts. Does that matter? No. Trenberth's energy budget is not a GCM, not predictive, but rather an overview of the data available adjusted for internal consistency. Running off and arguing about differences within the range of error of individual element uncertainties is not productive. Such decimal point gaming certainly has no traction in proving/disproving any element of the radiative greenhouse effect. I'll note that this discussion is rather off topic - unless, as you seem to be arguing, that you are attempting to find more evidence for the fact that the CO2 effect is indeed not saturated.
  15. RE my comment in 137, I inappropriately said "clouds probably absorb substantially more." I should probably withdraw that assumption upon the realization that while clouds cover on average of 2/3 of the surface, they make up considerably less of the total volume of the troposphere (7%, Lelieveld et al., 1989; Pruppacher and Jaenicke, 1995). This means the atmosphere has opportunities to absorb that same radiation before it reaches the clouds (in the lower, denser part of the atmosphere where there is substantially more CO2 and water vapor), as well as above the clouds. Comparing the outgoing LW radiation by latitude and season versus the cloud distributions by latitude and season demonstrates an even greater imbalance that must be addressed. Obviously, things are a lot more complex, and such a brash, broad assumption was unwarranted. Apologies for the error.
  16. #139 KR at 02:33 AM on 27 April, 2011 Very good; looking up the references. Which, I'll note, support the value in the 2009 paper. No, it does not. It supports only a claim the value in the 2009 paper should be at least 40 W/m2, but it can be larger by a wide margin. Trenberth fails to mention this detail. Does that matter? Yes, definitely. According to Trenberth there is a net heat transport of 23 W/m2 from surface to atmosphere by thermal IR radiation. On the other hand if global average window radiation is more than 60 W/m2, this heat transport is negligible and any net heat transport between surface and atmosphere is mediated by thermals and evaporation. That's a big difference. It means the greenhouse effect is saturated indeed. Surface and atmosphere is in radiative equilibrium (as it should) except for the fraction of radiation that escapes directly to space. For example if effective temperature of the surface is 289 K (16 °C), effective temperature of the atmosphere as seen from the surface is 277 K (4 °C) and window radiation is 62 W/m2, the above relation holds. Value of net heat transport by radiation between surface and atmosphere has enormous physical consequences, so you can't miss it by 10's of watts and still claim the physics is understood.
    Response:

    [DB] Again, please substantiate, or withdraw, your allegation of manufactured data made against Dr. Trenberth.

  17. Berényi - You continue to use a tabulation summary as a model. I would suggest you obtain a modern copy of MODTRANS or other radiation modeling code and look at the results yourself. You should also (as Trenberth did) cross-examine satellite spectra, cloud coverage estimation on a global scale, and distribution of humidity over both ocean and land. Once you've done so, and backed up your calculations, your numbers can be taken seriously. If operating from a summary that has been adjusted for internal consistency, with considerable uncertainty on some items - not even close. Please cf. my last link in this post. Again - are you retracting your accusation of manufactured data? I don't believe I'm alone in finding that deeply insulting to Trenberth et al.
  18. 142, KR,
    I don't believe I'm alone in finding that deeply insulting to Trenberth et al.
    Agreed. Insulting, unfounded, and pretty far over the top (as if his energy budget diagram is or was intended to be anything more than a back-of-the-envelope presentation of energy flow in the system).
  19. 141, BP, I don't quite understand your comment. I think you just have some hurried mistakes in there. Perhaps you can correct them and re-post, or clarify things:
    ...net heat transport of 23 W/m2 from surface to atmosphere by thermal IR radiation...
    The 23 I see in the diagram is reflected visible spectrum radiation. There is also 17 W/m2, but that's for thermals, not "thermal IR radiation." It has nothing to do with radiated heat. Beyond this, you say:
    It means the greenhouse effect is saturated indeed.
    I don't follow you. That is, I don't follow how the proportion of energy from thermals to that escaping through the atmospheric window can have anything to do with whether or not the greenhouse effect is saturated, one way or the other. Honestly, I don't see how anyone could ever take any numbers from such a simple schematic and draw any conclusions whatsoever about the CO2 being saturated. Can you restate your logic more clearly?
  20. #142 KR at 06:04 AM on 27 April, 2011 Again - are you retracting your accusation of manufactured data? I don't believe I'm alone in finding that deeply insulting to Trenberth et al. Listen, I have not said data were manufactured. It just came from nowhere in that paper, that's all. And this claim is true, you can verify it for yourself. "That 40 W/m2 is not substantiated anywhere in the paper. It was just pulled into Fig. 1. out of thin air". Later on I have found the source in a paper written by the same author 12 years earlier, but the 2009 paper lacked any pointer to the source, window radiation is not even mentioned in the text. Also, the calculation in the 1997 paper is somewhat childish, to put it mildly. And presenting a lower bound as a best guess is misleading as well. More importantly, as the lower atmosphere is heated from below (by absorbed short wave radiation at the surface), most of it is either unstable or marginally stable. If there is excess heat at the bottom, it simply overturns the air column, possibly producing some precipitation (and releasing latent heat) as well instead of proceeding upward painfully by repeated radiation emission/absorption events. It is a well known fact thermal conductivity of gases is extremely low. When measuring this quantity, radiative and collisional heat transfer are not separated, so radiative heat transfer inside the atmosphere can't be substantial. Environmental lapse rate is 0.0065 K m-1 while thermal conductivity of air is 0.024 W m-1 K-1 (that of CO2 is even lower, 0.015 W m-1 K-1). It means upward heat transfer without mass exchange is about 0.16 mW/m2, which is negligible. If there is a ~23 W/m2 thermal flux in a substance along a 6.5×10-3 K m-1 temperature gradient (with no mass exchange), thermal conductivity is ~3.5 kW m-1 K-1, which is ridiculous. It is more than that of diamond (2.2 kW m-1 K-1), the best thermal conductor of all materials. In rare cases when there is a strong thermal inversion, radiative heat transfer may be somewhat larger, but still rather small compared to other fluxes (and its sign is just the opposite). If Trenberth's figures on surface radiation and back radiation are correct, physics tells us the global atmospheric window is some 50% larger than he claims.
  21. Berényi - You should, then, be aware that in English "pulled out of thin air" has extremely negative connotations with regard to numbers, namely "manufactured, made up, baseless". If you were not aware of the ramifications of that phrase, that's one thing. If you were intending it with the connotations attached, it's an accusation of data manufacture. Which is it?
  22. #145 - BP "It is a well known fact thermal conductivity of gases is extremely low." That is something of a cherry-pick, since it ignores the well-known effects of gases in motion. It is a well known fact that thermal conductivity of gases is extremely low, which is why gases make good thermal insulators if the possibility of convection is restricted, as in foams, wool fabrics, compressed straw, etc. It is a well known fact that thermal transfer rate of gases is extremely high if the refresh rate of air flowing over a surface is high, which is why CPUs, air-cooled engines, radiators of water-cooled engines etc. work so well at transferring heat. Fortunately, just like engineers, climate scientists know about convection and allow for it in their models.
  23. Berényi - Also note that in sea level pressure, in the saturated CO2 bands, absorption distance is ~10 meters, not zero, and this distance increases with altitude and reduced CO2 concentration. For unsaturated wavelengths this absorption distance is much further. Given that, I don't believe a simplistic thermal conductivity measure can incorporate radiative effects. Seriously, BP - you're obviously very intelligent. But a lot of very intelligent people have been working in this field for >100 years... if you think you have (once again - I recall about a dozen of these, in UHI, OHC, etc., that did not pan out) found an issue that all the bright people have missed, you might be correct. But it's far more likely that you've missed something.
  24. Sphaerica (RE: 137) "First, you can't just assume that because 1/3 of the sky is clear then that the clear sky absorbs 1/3 of the radiation." I'm not claiming the clear sky absorbs 1/3rd of the radiation. I'm saying that 1/3rd of the average surface radiation is emitted to the clear sky. This amount represents the theoretical maximum that can be emitted to space from the clear sky atmosphere, which is less than 169 W/m^2 emitted by the atmosphere depicted by the Trenberth diagram. "The ability to absorb long wave radiation is dramatically different between clear sky and clouds (clouds probably absorb substantially more, being made up of a powerful greenhouse gas, but I've never really seen any numbers on this)." I'm well aware of this. I don't see how this contradicts anything I've said. Using Trenberth's numbers, the cloudy sky absorbs 89% of the LW surface radiation emitted to it. The clear sky only absorbs 69% of the surface radiation emitted to it. "Clouds and the radiative properties of the surface are also not evenly distributed over the globe, either in space or in time. Everything else is not homogeneous." I never claimed it was. Relative to the energy balance, the averages (cloudy vs. clear sky) are what matter. "Second, you cannot ignore the non-radiative components (thermals and the release of latent heat)." I haven't. I'm well aware of them. "Third, and most importantly, you cannot ignore a major element which is not included in the diagram, which is the transfer of heat between "clear sky" and clouds. What happens when a cloud dissipates? Does the heat vanish? Is it forced to instantly radiate up to space? Does it fall to the ground with the rain?" No heat vanishes. It's either is radiated out to space, radiated down to the surface or returned to the surface in kinetic form mainly via precipitation. "Hint: When a cloud absorbs LW radiation, it is capable of transferring that heat to the surrounding and pervading atmosphere (remember, a cloud isn't a solid object, it coexists in space with the O2/N2 of the atmosphere). So it doesn't really matter which absorbs the radiation." What's your point? That the clear sky absorbs LW too? "The atmosphere (consisting of "clear sky" and clouds) absorbs the radiation, and the two cannot be separated into distinct components re this diagram." The average clear vs. cloudiness comes from the ISCCP data - not the Trenberth diagram. If, as you claim, the diagram is not depicting a 40 W/m^2 "window" through the clear sky and a 30 W/m^2 "window" through the cloudy sky with a total of 169 emitted by whole atmosphere, show me the power in = power calculations that demonstrate it. I have done so. "This diagram is not a GCM. It's just a diagram intended to help communicate the earth's energy budget to the casual viewer, and nothing more. You cannot read as much into it as you are attempting." I never claimed the diagram is a GCM. It's an energy budget diagram. With the exception of the ISCCP data on clouds, everything it taken directly from the diagram.
  25. 149, RW1,
    This amount represents the theoretical maximum that can be emitted to space from the clear sky atmosphere, which is less than 169 W/m^2 emitted by the atmosphere depicted by the Trenberth diagram.
    Wrong. You are discounting energy from other sources (such as thermals, latent heat, energy absorbed directly from the sun, and energy transferred from clouds to the "clear sky," as you call it). The input into the "clear sky" is 78 from the sun, 17 from thermals, 80 from latent heat, an unknown fraction of 396 from the surface, and an unknown amount transferred from clouds. You cannot separate the clouds from the clear sky with that diagram. You can't figure out how much energy the "clear sky" has to emit. You can't do it, except in the single, explicit case in the diagram where outgoing LWR is separated between clouds and "clear sky." You cannot back yourself into the numbers you'd like to see. You can't do it. You can't do it. (And even if you could, it has no bearing whatsoever on the topic of the post, i.e. whether the CO2 effect is saturated.)

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