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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 101 to 125 out of 151:

  1. Tom Curtis @#97 disputes that the heat transport from the surface into the atmosphere is almost a constant whatever the surface temperature. He cites: Increased wind due to increased temperature. Changed Lapse Rate. Change in surface emissivity. Change in conductivity of the air due to higher moisture content. These may all be true [I actually dispute Lapse Rate changes: the lapse rate is controlled by the total energy into the atmosphere - net radiation, condensation of water, conduction, which I claim is virtually constant. So the Lapse Rate is a constant and Lapse Rate feedback may be a furphy.] but the LHS of the equation is always the sunlight absorbed by the Surface. Unless the albedo or solar constant change, sunlight absorbed by the Surface is invariant. On the RHS we have: Surface Energy absorbed into the atmosphere (NET radiation, condensed water vapour, conduction) plus Surface Energy radiated direct to space through the window. This latter term is nearly a constant, particularly if CO2 is nearly saturated (which it seems to be. It might change by a few percent if CO2 doubles - I look forward to calculated values for a doubling of CO2). If CO2 doubles we know that the LHS decreases by approximately 1W/m^2 (increased absorption of sunlight by CO2 in the upper atmosphere). This will approximately balance any decrease in Surface radiation through the window, so the Surface Energy absorbed by the atmosphere will remain the same.
  2. In the headline post (advanced version) the author assumes a "final layer" which is a black body at 220DegK. I have three objections to this: 1. The "Final Layer" is nothing of the sort. Photons are emitted at all levels. Absorption ensures that most never make it out to space through the fog of overlying gas. The average emission height is determined by absorption. In general this level will be different for every frequency. 2. The atmospheric gases are not black bodies - nothing like black bodies. Unlike solids or liquids they do not emit a continuous spectrum, but preferred frequencies (lines), the envelopes of which both in detail abnd as a conglomerate are far from a black body. See http://spectralcalc.com/spectral_browser/db_intensity.php. A black body curve is not appropriate and the "blackbody temperature" cannot be used to estimate the average height of emission. 3. It is implied that the amount of energy absorbed is the difference between two blackbody curves. This is an erroneous view. Energy absorbed into the atmosphere is ALWAYS manifested as kinetic energy (atmospheric heat) at the point of absorption. That energy flows upward by convection and radiation, still manifested as kinetic energy. It is then radiated to Space by the GHGs, primarily Water Vapour, with a little from CO2 (15-18W/m^2) and Ozone. These GHG molecules are energised by collision with other air molecules (around 50 times per nanosecond) and if the energies are right and the star signs are right (ie around one chance in one hundred thousand) a photon is emitted at a preferred frequency. If that photon avoids absorption by other GHG molecules, it escapes to space and that energy is lost from the planet.
  3. novandilcosid @100, in 97 I identified several factors on the RHS of the equation that result in changes in value on the LHS, specifically, in changes to the back radiation. I also identified factors which cause relative changes to the value of the terms on the RHS of the equation. As your argument requires that the LHS determine the value the values on the LHS, but not in turn have their values determined by factors on the RHS, your argument fails because the value of back radiation has been shown to be partially dependent on RHS factors. Further, your argument also depends on the two non-evaporative values on the RHS being constant, and this has also been shown to be false. You chose to ignore that facts I have raised, and simply re-assert your position. Fine - that it your right, but it also make debate with you pointless and uninteresting. I will merely note that keeping your discussion factual seems a low priority to you. Curiously, not only are you uninterested in trying to grapple with the facts I presented, you then go on to refute your own case. First, you indicate that rate of evaporation per degree C is not known, but according to you that value follows by straightforward reasoning from the energy balance equation. Further, you indicate that both constant RHS with a 2.5% increase in evaporation per degree C and a decreasing RHS with a 5% increase in evaporation per degree C are reasonable suppositions. However, both suggest decreases in the value of the non evaporative terms on the RHS, and the second suggests a much larger decrease. These are terms you require to be constant which changing temperature for your argument to succeed, but now you entertain the notion that they are anything but.
  4. Tom Curtis wrote @103 above: "in 97 I identified several factors on the RHS of the equation that result in changes in value on the LHS, specifically, in changes to the back radiation." I think Tom is referring to a different equation to the one I have been using to establish that the Surface Energy absorbed by the atmosphere is nearly a constant, regardless of CO2 concentration or temperature. Naturally this would cause differences of opinion to arise! I have ignored Tom's interesting observations simply because they are not relevant to the case - they amount to identifying variations in terms on the RHS of the equation, and these variations do not affect the hypothesis. The equation I have been using is: Solar_Radiation_Absorbed_into_the_Surface = Surface_Energy_Absorbed _into_the_Atmosphere + Surface _Energy_Radiated_through_the_Window_to_Space The LHS of this equation is only affected by the solar constant, atmospheric absorption of sunlight, and planetary albedo. [It does not contain Back_Radiation, that is within the first term of the RHS.] The LHS is nearly constant. If CO2 is doubled we expect a REDUCTION of about 1W/m^2 due to increased atmospheric absorption of sunlight. On the RHS, if CO2 is doubled, there will be a decrease of Surface Energy escaping to space through the window. How much is unknown by me (it is the subject of this thread, but there does not seem to be a number being cited) but I would expect it is of similar magnitude to the change in the LHS - a DECREASE of about 1W/m^2. IF that is the case then the third term, Surface_Energy_Absorbed _into_the_Atmosphere is a constant. This term contains evaporation, conduction and net radiation, all of which are the varying quantities which Tom has identified. I make no comment on the veracity of his claims at this point, merely restating that this term must be nearly constant. Tom writes: "You chose to ignore that facts I have raised, and simply re-assert your position." I agree. I have ignored his points (this is not to say I don't find them interesting), as I believe them to be irrelevant to the point I have been making. The Surface Energy absorbed by the atmosphere is nearly constant, regardless of surface temperature or atmospheric CO2 content. The degree of saturation is central to this assertion.
  5. Tom Curtis wrote @#103 above: "Further, you indicate that both constant RHS with a 2.5% increase in evaporation per degree C and a decreasing RHS with a 5% increase in evaporation per degree C are reasonable suppositions. However, both suggest decreases in the value of the non evaporative terms on the RHS, and the second suggests a much larger decrease." Tom is correct. The terms within the term "Surface_Energy_Absorbed _into_the_Atmosphere" are Net_Radiation, Evaporation and Conduction. It is known that evaporation INCREASES with temperature. All authorities agree on that. What is not known is by how much. Is it 2.5% (models), 5% (measurement), or 6.5% (Clausius-Clapeyron, assuming constant RH ) per DegC? It is also known that Net_Radiation INCREASES with temperature. But it DECREASES with increased CO2 concentration (back radiation increases slightly as the average altitude from which CO2 earth-bound photons are emitted drops. This level is lower therefore warmer, so there is aqn increase in intensity.)
  6. Tom Curtis also wrote @#103: " it also make debate with you pointless and uninteresting. I will merely note that keeping your discussion factual seems a low priority to you." I expect that Tom would like to withdraw this remark. I hope that my two previous posts have in fact answered his criticisms in detail. If not, perhaps he would be so kind as to point out where not.
  7. novandilcosid @104, I am dropping the debate about the relation between evaporative energy transfers and net radiation. It is too time consuming, and so far as I can tell almost irrelevant to this topic. Indeed the only relevance I can see to global warming is that if your theory were true, the Green House Effect would be stronger than it is currently predicted to be. That is because if the energy flow to the atmosphere were constant with temperature, the energy flow from the atmosphere to space must also be constant with constant insolation regardless of surface temperature. Therefore any adjustment to reduced outgoing radiation due to green house gases must be entirely compensated for by changes in surface temperature, rather than partly compensated for by increased atmospheric temperatures as currently believed. So, unless you can provide a clear and succinct statement of your thesis and it relevance, I will consider it of topic and not worth the energy.
    Response: [DB] Fixed closing bold tag.
  8. novandilcosid @99 asks, ""[H]ow much additional surface energy is absorbed outside the saturated 625-725 band, ie by how much does the window close, in W/m^2? The following chart from SOD shows the change in net forcing from a doubling of CO2: The total forcing for such a doubling is, of course, 3.7 W/m^2, with the vast majority of that being in the wings. You will notice that this is the forcing at 200mb, ie the tropopause (as also for the graphs of transmitance and change in transmitance at @86 and 82 respectively. novan will of course point to the influence of the stratosphere, but that is greatly exaggerated by him, and for two reasons. First, to a reasonable approximation the energy in the stratosphere comes from UV radiation absorbed by ozone. Increasing the CO2 concentration does not increase that energy. Rather, it cools the stratosphere by radiating away that energy more efficiently. The result is a slight increase of radiation in the primary band of CO2 emissivity, but a reduction in the IR radiation by ozone (the other main gas that radiates energy away from the stratosphere). The result in zero net change in the OLR. The second effect relates to the exchange of IR energy between the top of the troposphere and the stratosphere. Increased CO2 concentration reduces IR radiation from the troposphere to the stratosphere, further cooling the stratosphere (although how strong this effect is a matter of debate). But the increased proportion of stratospheric energy radiated by CO2 means there is an increase in energy radiated from the stratosphere to the troposphere by CO2. This, however is again balanced by a reduction in the IR radiation emitted by ozone to the surface. In Line by Line and energy balance models, these effects are taken into account in determining the forcing at the tropopause. Radiative forcing is, after all, "The radiative forcing of the surface-troposphere system due to the perturbation in or the introduction of an agent (say, a change in greenhouse gas concentrations) is the change in net (down minus up) irradiance (solar plus long-wave; in Wm-2) at the tropopause AFTER allowing for stratospheric temperatures to readjust to radiative equilibrium, but with surface and tropospheric temperatures and state held fixed at the unperturbed values." Consequently the above graph of change in radiative forcing at 200 mb includes the effects of the changes in the stratosphere. Of course, novan may well dispute this, so the best thing to do is to got to empirical data. Novan's thesis is that the net effect of adding CO2 to the atmosphere is to increase radiation to space from CO2, thus cooling the Earth. (See 81 and 89 above). The following are graphs of the change in IR radiation (measured as brightness temperatures) between 1970 and 1997. Figure b top shows the change in the tropical Pacific (between 10 degrees north and 10 degrees south); while figure b bottom shows the "near global" changes (between 60 north and 60 south). The middle shows the tropical case as predicted by a model. The first think to notice is that in the CO2 emission wavelengths, the emissions are either reduced or barely increased in the tropical observations; and that for the "near global" observations and the simulation they are reduced. The second thing to notice is that the net radiation to space has increased in the tropical case (and possibly also, but slightly, in the "near global" case. This indicates an overall increase in temperature of the Earth/atmosphere system in 1997 relative to 1970 which is anomalously large compared to that expected by the GHE alone. The obvious reason for this is the 1997/1998 El Nino which commenced in April of 1997 (the data is for the April-June period). The obvious thing to do is to remove the temperature effects from the record. Doing so reveals graph C in the figure (and figure 1 in the article above) which shows a clear reduction radiation in the CO2 band. Thus novan's thesis is clearly refuted by the observational data.
  9. Tom Curtis responded at 107 to my very clear post at #104 in which I said: "Solar_Radiation_Absorbed_into_the_Surface = Surface_Energy_Absorbed _into_the_Atmosphere + Surface _Energy_Radiated_through_the_Window_to_Space The LHS of this equation is only affected by the solar constant, atmospheric absorption of sunlight, and planetary albedo. [It does not contain Back_Radiation, that is within the first term of the RHS.] The LHS is nearly constant. If CO2 is doubled we expect a REDUCTION of about 1W/m^2 due to increased atmospheric absorption of sunlight. On the RHS, if CO2 is doubled, there will be a decrease of Surface Energy escaping to space through the window. How much is unknown by me (it is the subject of this thread, but there does not seem to be a number being cited) but I would expect it is of similar magnitude to the change in the LHS - a DECREASE of about 1W/m^2. IF that is the case then the third term, Surface_Energy_Absorbed _into_the_Atmosphere is a constant. This term contains evaporation, conduction and net radiation, all of which are the varying quantities which Tom has identified. I make no comment on the veracity of his claims at this point, merely restating that this term must be nearly constant." Tom said: "unless you can provide a clear and succinct statement of your thesis and it relevance, I will consider it of topic and not worth the energy." I am somewhat at a loss as to how to proceed. My post is very clear, and no error has as yet been demonstrated, Tom's previous efforts having been irrelevant to the discussion as they did not address the clear statements made. For the record: 1. All the solar energy absorbed into the surface must be exported from the surface. 2. There are only two places that energy can go, either into the atmosphere or out into space. 3. The solar input is nearly constant (there is a small reduction if CO2 is increased) and we expect a small reduction in the export to space (the window slightly tightens). 4. That means that the export of energy from the surface into the atmosphere is nearly constant regardless of temperatures and CO2 concentrations There are a couple of things to note: 5. The above assumes integration over the whole surface for one year then averaging. It also assumes a planet in equilibrium with Space. 6. A constant energy flow from the surface into the atmosphere means a constant lapse rate. The lapse rate does not change with more evaporation, because any increase in evaporation is offset by decreases in energy flows from net radiation/conduction. 7. It is untrue to say that increasing CO2 increases the amount of surface energy trapped by the atmosphere. That energy entrapment is essentially constant.
    Response: (DB) Except that the energy balance at the TOA is not balanced; thefore the planet is not in equilibria in its energy budget. Your argument therefore fails this initial test.
  10. Tom Curtis posted at #108: "novandilcosid @99 asks, ""[H]ow much additional surface energy is absorbed outside the saturated 625-725 band, ie by how much does the window close, in W/m^2?" The following chart from SOD shows the change in net forcing from a doubling of CO2... I note in passing that increased Radiative Forcing (=energy inbalance at the Tropopause) is entirely different to increased absorption of Surface Energy, so that Tom's entire post is a confusing non-response to the question. Does anyone have a figure for the decrease in Surface Energy passing through the window due to a doubling of CO2 and assuming no temperature change at the surface?
    Response: (DB) Your final assumption is flawed so your question is meaningless.
  11. Tom Curtis posted at #108: "The result in zero net change in the OLR." Working again on the model of a planet where energy flows are integrated over the surface for a year, then averaged, and assuming the planet is in energy equilibrium with Space, we can write: Sunlight hittng the planet = reflections + sunlight absorbed then reradiated. or, put another way, Sunlight hitting the planet = Outgoing Shortwave Radiation (=reflections) + Outgoing Long Wave Radiation (sunlight absorbed and reradiated) It is clear from this that OLR varies only if the Earth's albedo changes. It is sometimes claimed that the warming effect of GHGs must mean OLR is increasing or perhaps decreasing. But not in an equilibrium planet with no change in cloud or ice cover.
  12. DB reponded to my post at #109 with "Except that the energy balance at the TOA is not balanced; thefore the planet is not in equilibria in its energy budget. Your argument therefore fails this initial test." He is sort of correct: on short timescales and at particular locations, the planet is not in equilibrium with Space. The energy balance changes from positive to negative all the time. But INTEGRATED on long timescales that balance has to be stable. Otherwise the planet will change to make it so. For example over the last 10 years the planetary average temperature has not changed. So the integration of energy input/output will be balanced or nearly so. That's what the Kiehl & Trenberth diagram used by the IPCC in 2007 says. (or are we saying that the IPCC was wrong to use that diagram?) I fail to see therefore why my innocous observation that there is no change in surface energy into the atmosphere is invalidated.
    Response:

    [DB]

    "But INTEGRATED on long timescales that balance has to be stable. Otherwise the planet will change to make it so." 

    On very long timescales, it is in balance.  Right now, due to the forcing from CO2, it is not.  So the planet is seeking to regain that balance by raising the tropospheric temperatures as well as sequestering heat/energy into the oceans.  This is very basic, PRATT stuff.

    "For example over the last 10 years the planetary average temperature has not changed."

    Incorrect.  This fails on multiple levels:

    1. The global temperature record shows the most recent 10 year period as the hottest in the instrumental record.
    2. Selecting a short 10 year period is cherry-picking, as that period is typically too short to carry statistical significance.  However, allowing for exogenous factors, the planet has shown statistically significant warming since 2000.

    I fail to see, therefore, why you cannot see your position is invalidated from the initial premise.

  13. novandilcosid @110, your post to which I responded asked both about the change in transmittance (aborption of surface radiation), and the change in atmospheric emissions at the top of the atmosphere. This first was shown clearly in post 82. The combined effect was clearly shown in my first figure @108. You dismiss that because that highly relevant data was not in the exact format your required to impose your spin. You at the same time simply ignore the impirical data that refutes your thesis. Well, your game is now very clear, and it is not honest inquiry. If you ever want to try that, run a full Line By Line calculation of the emissions spectrum (as has been done by the people whose results you simply dismiss), and then if you come up with an interesting result, try again. In the mean time, I am not interested in pretending the partial calculation of a result on the back of an envelope can in any way refute the full calculation of the result with computers using a variety of methods, all coming up with essentially the same result.
  14. In response to my question "Does anyone have a figure for the decrease in Surface Energy passing through the window due to a doubling of CO2 and assuming no temperature change at the surface?" DB wrote: " Your final assumption is flawed so your question is meaningless" The whole of this thread is about how much the window closes (note: not about the export to space but about the absorption of radiation). I'll ask the question a different way: "What is the percentage change in the proportion of surface radiation absorbed by CO2 for a doubling of CO2?"
    Response:

    [DB] As the OP shows, the whole of this thread is about:

    "If the CO2 effect was saturated, adding more CO2 should add no additional greenhouse effect. However, satellite and surface measurements observe an enhanced greenhouse effect at the wavelengths that CO2 absorb energy. This is empirical proof that the CO2 effect is not saturated."

  15. novandilcosid at 15:19 PM on 25 April, 2011 David Archer (Univ. Chicago) made available online an older version of Modtran. I'm not sure how accurate it is, but you may find it a helpful tool to play around with that kind of hypothesis.
  16. novandilcosid, I note again that you are not really arguing that the CO2 greenhouse effect is saturated... you are arguing that it does not exist at all. Yet you have refused to respond to the obvious questions that raises: 1: Why do Spencer, Christy, Pielke 1&2, and every other 'skeptic' scientist (not to mention all mainstream scientists and all physics texts on the subject) claim that CO2 DOES cause the planet to be significantly warmer than it would be without? 2: If CO2 and other atmospheric gases can only slightly decrease the amount of radiation reaching the surface and thus cause slight cooling as you claim, then why is the Earth more than 30 C warmer than could be explained by sunlight hitting an airless rock at this distance from the Sun? You stand at odds with nearly two centuries of scientific understanding. How do you explain that? You argue that energy in must equal energy out (though this isn't true when a system is not in balance), but ignore the fact that this says nothing about the actually relevant issue of energy within the system. Consider a house (or planet Earth) which is receiving a fairly constant influx of energy from a furnace (or the Sun). Once equilibrium is reached the energy leaving must be equal to the energy entering... but the amount of energy within the system can be very different depending on how much insulation (or greenhouse gases) it has. One constant energy source... constant energy emission from the system... but DIFFERENT amounts of energy within the system and therefor different temperatures. Ergo all your arguments about energy in and energy out are irrelevant. The question at hand is energy within the system.
  17. novandilcosid (RE: 110), "I note in passing that increased Radiative Forcing (=energy inbalance at the Tropopause) is entirely different to increased absorption of Surface Energy, so that Tom's entire post is a confusing non-response to the question. Does anyone have a figure for the decrease in Surface Energy passing through the window due to a doubling of CO2 and assuming no temperature change at the surface?" The figure is 3.7 W/m^2. When CO2 is doubled, the window (i.e. transmittance) reduces by 3.7 W/m^2 and the atmosphere absorbs an additional 3.7 W/m^2 of surface emitted radiation, half of which goes down to the surface and half of which goes up out to space (1.85 W/m^2 up and down). It has been claimed here and elsewhere that the halving effect is already accounted for in the 3.7 W/m^2 figure; however, I have not been able to verify this through numerous inquiries to the climate science community. No one can give me a straight answer, but I'm still working on it.
    Response: (DB) In reality, you were given an answer, which you have chosen to ignore.
  18. novandilcosid (RE: 110), If the net effect at the surface is 3.7 W/m^2, then the "window" should close by 7.4 W/m^2 when CO2 is doubled.
  19. I should say the "window" should decrease by 7.4 W/m^2 when CO2 is doubled (not close). Trenberth et al 2009 has the window being 70 W/m^2 with the atmosphere emitting 157 W/m^2 down and 169 W/m^2 up (48% down and 52% up), if your interested in running some numbers.
  20. RW1 - Your erroneous "halving" has been addressed repeatedly, you have simply chosen to disregard the answers you have received. 3.7 W/m^2 is the drop in IR emitted to space for a doubling of CO2. This is due both to the rise in tropopause and effective emission altitude from increased CO2 concentration (and hence lower CO2 emitting temperature) and absorption band expansion. The window decreases slightly, but the predominant change is decreased emissions across the CO2 absorption bands. Hence "If the net effect at the surface is 3.7 W/m^2, then the "window" should close by 7.4 W/m^2 when CO2 is doubled" is simply wrong. There are two effects, not one, and your insistence on assigning all change to one effect has been corrected over and over again. Anyone interested in that discussion should look at the Lindzen and Choi thread, where RW1 and others were informed of the details over 448 postings. Please do not rehash that here. This thread is about CO2 saturation, and it is hence off-topic.
  21. Re: my past post - CO2 effects are on topic. However, George White/co2isnotevil's incorrect assumptions about 'halving' really are not. 3.7 W/m^2 is the decrease in IR leaving the atmosphere for a CO2 doubling, as per line-by-line multi-level atmospheric modeling, CO2 spectra and physics, and confirmed by top of atmosphere satellite measurements. No 'halving' occurs.
  22. RE: DB and KR, I haven't ignored or disregarded anything. Just because I was given an answer doesn't mean it is the correct answer. I'm still working on the issue and hope to eventually resolve it once and for all.
  23. KR (RE: 121), You even stated the following here: "As has been said here, repeatedly, the 3.7 TOA number means that 7.4 W/m^2 is being absorbed and radiated isotropically from CO2." There is definitely a halving effect. The fundamental question is if the 3.7 W/m^2 represents the post or pre halving effect. If it represents the post halving effect, as claimed here, then the "window" or transmittance (i.e. the amount of surface emitted that passes straight through the atmosphere unabsorbed and goes out to space) should reduce by 7.4 W/m^2.
  24. novandilcosid, I don't want to rehash this debate here. See the posts by 'co2isnotevil' and myself in the following threads: Here and Here Also, this paper by co2isnotevil: "Proof that only half of absorption affects the surface"
  25. RW1 - 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), as increased CO2 concentrations raise the level of effective tropospheric radiation to colder altitudes. Why are you disregarding that very significant effect? Why are you claiming that all of the IR decrease occurs by a reduction of the 40 W/m^2 window, when that is clearly not the case?

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