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Plass and the Surface Budget Fallacy

Filed under: — raypierre @ 13 January 2010

RealClimate is run by a rather loosely organized volunteer consortium of people with day jobs that in and of themselves can be quite consuming of attention. And so it came to pass that the first I learned about Gavin’s interest in the work of Plass was — by reading RealClimate! In fact, David Archer and I have a book due to appear this year from Wiley/Blackwell (The Warming Papers), which is a collection of historic papers on global warming, together with interpretive essays by David and myself. Needless to say, we pay a lot of attention to the seminal work by Plass in this book. His 1956 QJRMS technical paper on radiative transfer, which is largely the basis of his more popular writings on global warming, was one of the papers we chose to reprint in our collection. In reading historic papers, it is easy to fall into the trap of assuming that investigators of the past are working on the basis of the same underlying set of assumptions in common use today. Through a very close reading of the paper, David and I noticed something about the way Plass estimated surface temperature increase, that Gavin and all previous commentators on Plass — including Kaplan himself — seem to have overlooked.

These days, it is fairly common knowledge that determination of surface temperature change requires simultaneous satisfaction of the top-of-atmosphere energy budget and surface energy budget, and that in most circumstances it is the top-of-atmosphere budget that plays by far the leading role. This is one of the many things that Arrhenius got spot-on right in his conceptual framework for computing surface temperature. His computation explicitly takes both balance requirements into account, though substantial inaccuracies were introduced because the onerous computations involved in solving the model pretty much restricted him to a one-layer representation of the atmosphere. Later workers improved on Arrhenius by introducing multiple layers and more accurate spectroscopy, but did not always note the importance of satisfying the top-of-atmosphere balance. I think it seems natural to most people to assume that if one is interested in surface temperature, the surface budget must be the most important thing to look at. Plass, for all his brilliance in computing the radiative effects of CO2, was one of the ones who was led astray by this fallacy.

Since discussions of radiative forcing today are almost invariably based on top-of-atmosphere budgets (or at least top-of- troposphere budgets, which are almost the same thing), it is natural for the modern reader to assume that when a paper quotes a radiative forcing, it must be a top-of-atmosphere forcing. This is what Gavin assumed, but a close reading of the 1956 QJRMS paper shows that this is not, in fact, what Plass was talking about. In that paper, Plass does not get around to turning his voluminous radiative calculations into a surface temperature change until nearly the last page of the paper, and when he does, he spends barely a page explaining the reasoning.

The radiative forcing Plass quotes is actually the increase in downward infrared radiation to the surface, which you get if you double CO2 while holding the atmospheric temperature fixed . This back-radiation increases because increasing the concentration of a greenhouse gas makes the atmosphere a more efficient emitter of infrared radiation, at least up to the point where the lowest bits of the atmosphere emit so well that they essentially have become a blackbody, whereafter the emission to the ground can no longer increase unless the air temperature changes. For Earthlike conditions, the emission from CO2 is nowhere near saturated in this sense (see this post ) , so Plass was entirely correct in inferring an increase in the back-radiation, at least for a relatively dry atmosphere. Adding CO2 to the atmosphere is a bit like turning up the dial on a heat lamp you are lying underneath.

It is in the final stages of the calculation that Plass went wrong. He assumed that the surface would get rid of the extra infrared radiation it was receiving by heating up until it was able to radiate away the excess. This reasoning ignores the fact that radiation is not the only means of exchanging heat between the atmosphere and the surface. There are also turbulent exchanges, including evaporation, and these would tend to limit the surface warming to values far less than the values Plass estimated. Further, when the lower atmosphere is warm and moist, such as in the tropics, the great infrared opacity of the large quantity of water vapor tends to limit the direct effect of CO2 on back-radiation into the surface, which further limits the surface warming if the air temperature is held fixed as Plass did. To be fair, Plass does include a sentence implying that he was concerned about the portion of the retained flux that exited through the top of the atmosphere, but even if one gives the most generous interpretation to what might have been meant by this statement, there is no way to make a consistent calculation out of it, given the use of the surface back-radiation as radiative forcing.

The way the greenhouse effect really works is that adding CO2 reduces the infrared out the top of the atmosphere, which means the planet receives more solar energy than it is getting rid of as infrared out the top. The only way to bring the system back into balance is for the whole troposphere to warm up. It is the corresponding warming of the low level air that drags the surface temperature along with it — an effect left entirely out of Plass’ calculation.

A more quantitative discussion of the way all this works can be found in The Warming Papers, and a yet more advanced discussion of such things can be found in Chapter 6 of my book Principles of Planetary Climate (which at long last has been shipped off to Cambridge University press, animula vagula blandula)

In point of fact, Plass did compute the top-of-atmosphere radiative forcing due to doubling or halving the concentration of CO2. The result is plainly shown in the rightmost graph of his Figure 7, where he shows the vertical profile of upward and downward flux for three different CO2 concentrations. Reading the values from the top of the graph, I get that Plass computes a 3.2 Watt per square meter reduction in the outgoing radiation for a doubling of CO2. This is really quite close to the modern value. Plass does not mention this number, or its importance, anywhere in the text, however. Still, it would be fair to give Plass the credit for the first calculation of top-of-atmosphere radiative forcing using correct modern radiative physics. Though he did not make good use of the calculation himself, the methods he introduced are largely the same as those used by Manabe and Wetherald in 1967, who were the first to put together correct spectroscopy with a correct framework for computing surface temperature, adding in accurate water vapor spectroscopy and the effects of convection along the way.

Thus, while Plass made seminal contributions to radiative transfer, his actual estimate of surface temperature increase cannot be regarded as an improvement over Arrhenius. Plass had better spectroscopy than Arrhenius, but a framework that would not give the right answer no matter how good the radiative transfer was. The point of all this historical deconstruction is not to poke fun at Plass or detract from his contributions. Theories do not spring from scientists full-formed like Athena from the head of Zeuss. Science often proceeds through a series of errors and corrections, and those who move the ball forward are in the thick of this process even if they have made some mistakes. The point is that our current understanding of global warming rests on the shoulders of some of the greatest giants of physics of the past century or more, and myriad lesser but still substantial intellects as well.

So, when push comes to shove, was Plass a Hedgehog or a Fox? The answer is: a bit of both. With regard to computing the radiative fluxes due to CO2, Plass was a true hedgehog — he knew that one thing really, really well, and that had a lasting impact on our science. But in his Tellus article, he also showed himself to be quite a fox, in that by knowing (and explaining) many independent lines of thinking, he helped to revive attention to the wide-ranging importance of CO2 in climate. You could say he was not enough of a fox to have also absorbed the lesson of the importance of top-of-atmosphere balance, known already to Arrhenius. But also, you could say that if you’re going to be a hedgehog and pick one thing to be the central organizing principle of your world view, it had better be a pretty darn universally important thing to know. If you’re going to be a climate hedgehog, the constraint imposed by top-of-atmosphere radiation balance would be a pretty good place to hang your hat.

230 Responses to “Plass and the Surface Budget Fallacy”

  1. 101
    Hank Roberts says:

    PS, for Jim and anyone having trouble with that picture: (discussion before publication)



    An update of the Earth’s global annual mean energy budget is given in the light of new observations and analyses. Changes over time and contributions from the land and ocean domains are also detailed.

  2. 102
    John E. Pearson says:

    100: I’ve read a fair bit of Weart’s site. I gave his book to my son for Christmas. I think the picture I sketched is essentially what Timothy Chase wrote in 82 except my reading of Chase’s comment made it sound as if he was describing a fixed TOA elevation. I thought it was also about what Ray Pierre described in the article that started this thread although there is plenty I’m not clear on. What I’d really like to see is a simple model of the sort that you might expect to find in Haliday and Resnick. Then one wouldn’t have to wonder exactly what was meant. I believe that would also answer the boundary condition stuff that Geoff Wexler was wondering about above. Barton’s saturation page comes close, but I don’t think it contains the change in radiation at the TOA (unless I missed it). I presume that such a model exists in some atmospheric physics book somewhere?

  3. 103
    Paul Harris says:

    The author of the piece referred to in 43 above is a right wing conspiracy theorist. One of the organisations that he heads: Environmental Perspectives Inc. argues that environmentalists and proponents of AGW are plotting to impose world government and paganism. On the website of his other organisatoin -Sovereignity International- you czn watch a clip of Lord Monkton explaiing how the ex-commies who now run the green movement are going to use the Copenhagen ‘Treaty’,which he has read,to impose world government on us. “I was blinded by the light” as Manfred Mann used to sing.

  4. 104

    Raypierre, is Principles of Planetary Climate scheduled for Australian publication? (I think we have some sort of protectionism here to support local printing.) If not I’ll look out for it in Amazon.

  5. 105

    101 Hank Roberts,

    Thanks for the added info.

    I added 494 and -493 and got zero. For this kind of numbers that is a correct answer.

    However, I note that there is a .9 W/m^2 of heat going into the surface, and this is average for land and sea. That would still be zero in a reasonable analysis. Especially when trying to account for heat uptake by the oceans of 10×10^23J as indicated by the NOAA chart I referenced earlier.

    [Response: Why? It is an estimate of the net uptake of heat in the ocean over the most recent decade. It is very unlikely to be zero. - gavin]

  6. 106

    #63 Completelyfedup

    I may have confused the matter by talking about “vertical mixing” without noting that I refer to vertical mixing in the ocean.

    I guess your curved ruler story is saying that the heat going into the ocean is negligible. That is a curious comment in the face of 10×10^23J going there over twenty years.

    Reference for that number is the NOAA chart in the Dec 28 2009 post here at realclimate. It is my conclusion that this heat into the ocean is enabled by vertical water motion that would carry heat of that magnitude down to lower levels. That vertical water motion acts to a depth that is a function of wave height which is a function of wind which is a function of temperature at the surface. Are these things in question?

  7. 107
    marlys says:

    56: Minor point but Michael Coffman does _not_ write for Project Censored. Coffman is a straight up fundamentalist Christian endtimer, a denier, a winger, and a propagandist for hire. Coffman is an environmentalist only to, in his words, warn people of the “dangers of the environmental movement and how false environmental catastrophes like global warming are being used to justify the need for world government and a pantheistic-based…religion.”

    The link on the Project Censored page is to the August Review and, yes, August Review did recently publish a Coffman article that’s pretty standard denier fare. And, yes, the August Review has a thing for the Trilateral Commission that might extend to their views on global warming. Coffman seems to be peddling this, um, theory in some of his other writings but Project Censored certainly doesn’t suggest that “global-warming is a conspiracy of the Trilateral Commission”

    Project Censored is a mostly written by college journalism students as part of a class project. Sometimes it’s interesting and on target. Sometimes it suffers from being written by younger writers. However, it’s not terribly ideological–except to the extent that reality tilts left. I hate to see Project Censored tarred by the false accusation that they published, or approved of, a Michael Coffman article.

  8. 108
    Hank Roberts says:

    Jim Bullis

    .9 watts per square meter times how many square meters?

  9. 109
    Hank Roberts says:

    More for Jim:

    > into the ocean is enabled by vertical water motion

    But not everywhere, there’s far more lateral motion if you’re measuring distance traveled. Thermohaline circulation–>areas where water sinks, after heat transfer and mixing, other areas of upwelling.

  10. 110
    Brian Dodge says:

    Does the change in spectral characteristics from water vapor to liquid/ice in clouds(~60nm shift according to wikipedia) increase the back radiation by filling clear air spectral gaps? How much of the heat of condensation/freezing gets radiated back to the surface, and if there’s more latent heat transport, does that change the balance? Is H2O vapor + CO2 plus clouds a stronger greenhouse than just H2O vapor + CO2?

  11. 111
    Brian Brademeyer says:

    #97 Doug B,

    Gary’s dilemma was illustrated quite well in Monty Python’s ‘Life of Brian’ in the conflict between the ‘Cult of the Shoe’ and the ‘Cult of the Gourd’.

  12. 112

    Re gavin comment at #105

    Exactly my point. I am trying to show that the chart referenced in #101 is wrong because it shows virtually zero heat going into the ocean.

    It is very hard to actually find out what the climate models include. Apparently others have this problem as well.

  13. 113

    A question I keep getting asked by a “skeptic” is where can you find the basic theory of CO_2 warming (at quantum physics level, not a higher-level model). My suspicion is he is going to need to read a book but if anyone has a shorter reference, I’d like to hear about it. Meantime I am going to refer him to Raypierre’s book (and possibly dig out some of the text books it references from my draft copy, since it’s not available any more until it’s published).

  14. 114
    Tom P says:

    “Why? It is an estimate of the net uptake of heat in the ocean over the most recent decade. It is very unlikely to be zero. – gavin”

    Look at UAH?

    The current daily anomaly is the highest in their available records and just gone above the monthly peak of 1998. It looks like a lot of that energy stored in the oceans is currently being released.

    [Response: That's not really how it works. The global warming post an El Niño event is mostly from the changes in water vapour and cloud cover that alter the radiative balance, not just because heat is coming out of the ocean in the East Pacific (it is actually going into the ocean elsewhere for instance). I recall seeing a paper looking at this in more detail, but I don't recall the authors.... - gavin]

  15. 115
    Dave Werth says:


    Thanks for the answer. I do know that CO2 is well mixed in the atmosphere and that my idea was only a thought experiment. I was just wondering how much the CO2 level in the lower atmosphere matters* compared to how much it matters at the TOA relative to the ultimate surface temperature we see. If I use it in arguments with my skeptical friends and relatives I want to be accurate.

    *Of course lower atmosphere CO2 levels matter for things like ocean acidification.

  16. 116
    Ike Solem says:

    Funny how Coffman and Cockburn, ideologues of the so-called “left” and the “right”, join hands over the theme that climate science is really hiding an agenda for a communist world takeover (Coffman) or a fascist world takeover (Cockburn) – but then, maybe it’s just a puppet show… the most likely conclusion.

    As far as the direction that reality tilts in, notice that our universe is three-dimensional, not one-dimensional – as the left-right dichotomy would have it… though, interesting to note, a circle, viewed under a microscope appears linear… but as Coffman & Cockburn so neatly demonstrate, on a circle, if you move all the way to the left, you end up on the right… Let me guess – a secret non-aggression pact?

    Notice also that Plass didn’t include water vapor feedbacks in his calculations, as Gavin writes in the last post:

    However, Plass was well aware that the ‘no-feedback’ case was unrealistic and estimated that the water vapour, cloud and ice-albedo feedbacks would be amplifying, although he was not able to quantify them…

    Today, the water vapor effect seems to be fairly well-understood quantitatively, after:

    Science 26 April 2002:
    Vol. 296. no. 5568, pp. 727 – 730

    Global Cooling After the Eruption of Mount Pinatubo: A Test of Climate Feedback by Water Vapor

    Brian J. Soden, Richard T. Wetherald, Georgiy L. Stenchikov, Alan Robock

    The sensitivity of Earth’s climate to an external radiative forcing depends critically on the response of water vapor. We use the global cooling and drying of the atmosphere that was observed after the eruption of Mount Pinatubo to test model predictions of the climate feedback from water vapor. Here, we first highlight the success of the model in reproducing the observed drying after the volcanic eruption. Then, by comparing model simulations with and without water vapor feedback, we demonstrate the importance of the atmospheric drying in amplifying the temperature change and show that, without the strong positive feedback from water vapor, the model is unable to reproduce the observed cooling. These results provide quantitative evidence of the reliability of water vapor feedback in current climate models, which is crucial to their use for global warming projections.

    As far as classic papers, Manabe & Moller 1961 is worth plugging again – that’s one of the first to include the things left out by Plass & Kaplan:

  17. 117
    Completely Fed Up says:

    Dave Werth, two points to be made:

    1) So often such “thought experiments” come from people who, it later turns out aren’t thinking (see Septic Matt and Tilo for examples)

    2) If you don’t have CO2 in the lower part, then the CO2 will be less and the CO2 will diffuse out from the upper to lower atmosphere, reducing upper CO2.

    Rather like asking whether the foundations and ground floor of a block of flats really makes a difference, since nobody lives there apart from the curator.

    Sorry, three points

    3) your “skeptical” friends probably don’t want to know, so absolute accuracy isn’t needed from you. If they want the accurate, they can read the IPCC reports.

    4) and a fanatical devotion to the pope.

    sorry, wrong sketch.

  18. 118
    Completely Fed Up says:

    Jim Bullis: “Exactly my point. I am trying to show that the chart referenced in #101 is wrong because it shows virtually zero heat going into the ocean.”

    That isn’t a point, Jim. It’s begging the question: is there net heat going in to the ocean?

    If it is, then what is the wattage (this means, since the other elements are measured in watts per square meter) per square meter?


    And how does it compare to the insolation on the earth’s surface?

    If this is, say, as high as 1W/m2 then it makes no difference to the overall picture and its conclusion.

  19. 119
    Completely Fed Up says:

    “That is a curious comment in the face of 10×10^23J going there over twenty years.”

    That is a curious comment given that there isn’t anyone who integrates power over 20 years.

    Why did the scientists go over and produce the “Watt” as a joule per second if 20 years was the natural period to accumulate power..?

    Did you do that to BS with Big Numbers like Rod B (who is strangely silent when you’re doing it as opposed to Ray)?

  20. 120
    Geoff Wexler says:


    Isn’t there a super-idealized model

    If you go to

    and scroll down to 1896b in the Bibliography you can download the paper mentioned by Raypierre. The two boundary conditions are Eq.1 and Eq. 2. If you discard either of them you cannot determine either of the unknowns theta and T.

  21. 121

    Oh, God bless you, Raypierre, that sounds wonderful! I tried downloading the HITRAN database once and manipulating it myself, but I made a hash of it.

  22. 122

    Dappled Water,

    Thanks! These are great references!

  23. 123
    Geoff Wexler says:


    Many thanks for your helpful reply. I am beginning to understand, and I hope the other references , e.g. the surface energy budget chapter of your book will provide the detail.

  24. 124
    Luke Silburn says:

    Translating the NOAA number cited by Jim Bullis.

    10*10^23J works out to a W/m^2 figure once you have terms for:
    time (20 years = 6.31*10^8 s) and
    surface area of the ocean (per wiki, 3.61*10^14 m^2)

    multiplying these together gives 2.277*10^23 for your divisor.

    Handily the exponents cancel out, so 10/2.277 gives you 4.4 W/m^2. This is ~5 times the net surface absorbance given in that earth system schematic, so either I’ve mucked something up or there’s a complicating factor that is missing.


  25. 125

    Thanks again, CM!

    Alexandre, I emailed you the coefficients from my band scheme. There are 55 bands, 23 “shortwave” and 32 “longwave.” I treat them together, which is inefficient, but I was going for clarity of algorithm over efficiency.

  26. 126

    Peter Watts,

    I’m no expert, but I’m pretty sure immersing the Pope in nitric acid is a violation of canon law.

  27. 127


    At the atomic level, because electron orbitals are quantized, atoms can only absorb or emit photons at discrete frequencies (smeared out by uncertainty, etc.). Your CO2 absorbs an infrared photon, one of its electrons jumps a level, and it either radiates another photon of the same level, or more likely, crashes into a nearby nitrogen or oxygen molecule and transfers some of the new stuff as kinetic energy. Temperature is a measure of kinetic energy at the molecular level; the faster the molecules jiggle, the hotter the object. Thus the atmosphere warms up. Those collisions transfer energy *back* to the CO2, which radiates by the (wavelength-specific) Stefan-Boltzmann law. Some of the energy goes back down to the surface and heats it above what it would be from sunlight alone.

  28. 128
    Hank Roberts says:

    > 105, 112
    > I am trying to show that the chart referenced in #101 is wrong
    > because it shows virtually zero heat going into the ocean. –Jim Bullis

    Jim, please–read the text labels on the picture. The surface is what’s below the atmosphere: land and water, blue and brown.

    Read the paper.

    Right at the top in the hilighted area:
    “Changes over time and contributions from the land and ocean domains are also detailed.”

    Right in the beginning section:
    “The transmitted radiation is then either absorbed or reflected at the Earth’s surface. Radiant solar or shortwave energy is transformed into sensible heat, latent energy (involving different water states), potential energy, and kinetic energy before being emitted as longwave radiant energy. Energy may be stored for some time, transported in various forms, and converted among the different types, giving rise to a rich variety of weather or turbulent phenomena in the atmosphere and ocean.”

    You can look it up. Don’t trust me, read the source.

  29. 129
    Blair Dowden says:

    I understand that the greenhouse effect warms the planet because greenhouse gases raise the altitude at which the Earth radiates energy into space. Because temperature decreases with altitude, this causes less energy to be radiated, and more energy retained by the Earth. But at the stratosphere temperature starts increasing with altitude. My question is at what level of carbon dioxide will the warming effect be reduced by raising the radiating altitude into the stratosphere?

    [Response: This never happens. As you add more CO2, the stratosphere moves higher up, too. Venus has 300,000 times as much CO2 in its atmosphere as Earth and still hasn't exhausted its capability to get more greenhouse effect out of CO2. The stratosphere has moved up to where it is under 1% of the mass of the atmosphere. --raypierre]

    Also, following up on a previous discussion, how much carbon dioxide is required to lead to a runaway greenhouse effect?

    [Response: The answer is surprising, but the runaway greenhouse is determined by the solar constant and the planet's gravity. Adding CO2 in general will never trigger a runaway if the other conditions are not right. That's because water vapor dominates the atmospheric infrared opacity in a runaway state. There are some marginal states where adding CO2 can push things over the brink, but the Earth is nowhere near that. I'm not sure Jim Hansen understands this. To be fair, there is virtually no understanding of the way clouds affect the runaway greenhouse. --raypierre]

  30. 130
    tharanga says:

    re: in-line response 114:

    The forgotten authors might be Trenberth et al; I’d perused some papers from him about ENSO. The paper in question might not be JGR-Atmosphere 2002, DOI: 10.1029/2000JD000298, but should at least cite it.

  31. 131
    Geoff Wexler says:

    Re: #127 BPL

    Sorry to be pedantic but “one of its electrons jumps a level” is not quite right. In the case of a vibrational level, the excitation energy is probably equally divided between the motion of heavy nuclei (C and O) and the stretching and compression of covalent chemical bonds. It is true that the latter involves a change of electronic configurations but that is not correctly described by anything happening to one of its electrons.

  32. 132
    Ray Ladbury says:

    BPL, A nit. The state excited by IR in CO2 is vibrational, so you are looking at harmonic oscillation of the atoms–still quantized, but the HO rather than electron energy levels.

  33. 133

    Oops. Been a while since my intro chem class at CMU. Sorry about that.

  34. 134
    John E. Pearson says:

    120: Geoff, thanks. I see what you’re saying although I was hoping for something a bit different. I think
    that Arrhenius’ work was vulnerable to saturation arguments since it had only a single layer of atmosphere. There is this simple picture (my version of the simple picture is in post 83 which I think is what I’ve read). There must be a minimal model that goes with that picture, which gives the right qualitative behavior for radiation from the top of atmosphere and the concentration of atmospheric CO2. I am thinking of something which doesn’t have a zillion absorption bands etc. By minimal I mean; toss out any piece of it and it fails. From what I can tell, the climate scientists have a fairly concrete picture in mind and presumably this simple picture has been turned into a simple mathematical model like you might find in an undergraduate physics text? Perhaps its so standard that no one can believe my ignorance or so obvious or useless it isn’t worth writing down. Still it seems like such a model would be useful pedagogically, but that’s just me.

  35. 135
    Spaceman Spiff says:

    @129, you asked: “My question is at what level of carbon dioxide will the warming effect be reduced by raising the radiating altitude into the stratosphere?”

    Never. It’s a losing game. You mistake the highly wavelength dependent opacity of CO2 for one that is gray and narrowly confined to a band in wavelength. Every wavelength at which earth’s atmosphere is optically thick will escape at its own characteristic height in the atmosphere. Keep pumping up the CO2, and the number of watts/m^2 that radiates into space will continue (in net) to go down. In the face of the resulting rise in temperature of the troposphere, a lot more water vapor will find its way there and add further to the atmospheric IR-opacity. And of course you can’t expect that the temperature profiles within the troposphere and stratosphere to remain as they are today.

    Now, if you asked “when does the strongest emitting band of C02, which is centered near 15 microns, find its effective emitting layer in the stratosphere?” Playing around with David Archer’s online Modtran program, this occurs for C02 concentrations exceeding ~20 ppm (all else being equal).

    At least that’s *my* understanding; the experts may correct me.

  36. 136
    Completely Fed Up says:

    JEP: “I think that Arrhenius’ work was vulnerable to saturation arguments since it had only a single layer of atmosphere. ”

    This is not a new thought:


    Experts could dismiss the hypothesis because they found Arrhenius’s calculation implausible on many grounds.

    The logic is rather simple once it is grasped, but it takes a new way of looking at the atmosphere — not as a single slab, like the gas in Koch’s tube (or the glass over a greenhouse), but as a set of interacting layers.

    And scientists were coming to see that you couldn’t just calculate absorption for radiation passing through the atmosphere as a whole, you had to understand what happened in each layer — which was far harder to calculate.

  37. 137
    Frank Giger says:

    Geoff, you’ll have to forgive the “jumping up/down” of electrons in levels or orbit when discussing energy states of atoms and molecules from most folks.

    Excitement due to energy is taught in beginning courses (even at the college level) as electrons hopping about to higher and lower orbits – or at least was in the early 1980′s. :)

    The “pocket physics” demonstration I used to teach my son about both convection and Brownian motion is to gently pour some creamer into a hot cup of coffee. The creamer goes straight to the bottom, being cooler, but warms, climbing up in the center (following the natural convection within the coffee cooling around the sides of the cup), until it reaches heat equilibrium. At that point Mr. Brown takes over and diffusion happens from all that bouncing against each other.

    Of course there is just the physical mixing when an eight year old gets tired of lectures and puts the spoon in.

    Anyhow, I was talking to my (now) teenager about energy loss through radiation into space, and we revisted the coffee cup, and I was very pleased to see a light bulb go off in his head; I just hope it wasn’t the wrong color and I lead him to the wrong conclusions.

    We postulated the the planet either deflects or radiates more energy than it retains from the sun’s output to us, and is probably pretty inefficient at holding on to that energy.

    The greenhouse effect is more about retaining the gained energy introduced by the sun (we ignored warming of the crust by the mantle as the agreed assumption was it is a constant) by creating a better mixture of gases to increase efficiency. Or so we reasoned.

    CO2 isn’t the best GHG in efficiency, but the sheer amount of it in the atmosphere makes it an effective one; I suspect, however, that the levels required to generate a “runaway” greenhouse world would be impossible to achieve.

    Being both lazy and short of time to do the research, is the radiative properties of the upper atmosphere as sensitive to the relative composition of the gas there as it is to heat retention in the lower atmosphere?

  38. 138
    Blair Dowden says:

    Re 129: Thanks, raypierre. But why does the stratosphere move up with more CO2? Burning carbon replaces O2 with CO2, so the atmosphere does not gain more molecules. Does a warmer troposphere raise the boundary, so the stratosphere becomes smaller, or at least loses mass?

  39. 139
    Nelson says:

    116- As a leftist, Cockburn makes a fool of himself. Most on the left (as they tend to be more educated – with some crazy exceptions like Cockburn) are on the side of science, though. It is misleading to frame this as a left vs right issue, although it is not a coincidence that most of Palin’s partisans believe human induced climate change is a hoax or an alarmist story to benefit “green research.” I prefer to frame it as science vs. anti-science.

  40. 140
    John E. Pearson says:

    136: Fed Up: I wasn’t claiming that Arrhenuis work being vulnerable to saturation was a new thought. I was trying to explain that I would like to see a minimal model that is not vulnerable to saturation arguements. I keep hearing climate guys making this beautiful argument about radiation from the top of atmosphere that I tried to sketch in 83 and that others in this thread have discussed as well but basically it boils down to adding CO2 is equivalent to getting a thicker down comforter. I figure there must be a minimal model that corresponds to that picture and that it is probably in a book/article somewhere.

  41. 141
    Completely Fed Up says:

    ” Blair Dowden says:
    15 January 2010 at 12:17 PM

    Re 129: Thanks, raypierre. But why does the stratosphere move up with more CO2? ”

    Try reading the posts again.

    Post 82. This thread.

    If anyone wonders why I picked that monicker, see Blair’s post…

    [Response: The simple answer is that adding CO2 cools the stratosphere by increasing the infrared cooling, which makes it less stable and allows the tropospheric convection to reach to higher levels. That sounds pretty plausible, but it's not as inevitable as it sounds, because the stratospheric cooling competes with other effects. It is possible to concoct a hypothetical gas for which the stratosphere becomes thicker (the tropopause approaches the ground) as more greenhouse gas is added, but I don't know of any actual gases that behave this way. There is some discussion of this in Ramanathan's paper where he rediscovers Sagan's window-grey model without knowing Sagan did it first, but it's not widely known. So I put it in Chapter 4 of Principles. --raypierre]

  42. 142
    Geoff Wexler says:

    re #65 Ray Ladbury (nearly OT)


    He went so far right that he came back around on the extreme left.

    Correction: Apply a time reversal. There is long article about him on Wikipedia. His attacks on global warming science should be seen in the context of his (his movement’s) accusation that the UK Queen was involved in drugs and the Omaha City Bombing was part of a British plot. But for some reason he has been keen on fusion power.

  43. 143
    Tony Noerpel says:


    Regards your reply to Blair Dowden #129, in your own paper you describe recovery from a snowball earth. Isn’t it the current hypothesis that volcanic CO2 emissions built up over millions of years which could not be drawn down since the carbonate silicate cycle was stuck because the oceans were frozen over and there was no water vapor?

    But when the ice started melting, wouldn’t that have caused a hellaceous hot house? And even then the climate didn’t runaway. Of course the sun was cooler then.

    Pierrehumbert RT 2005: Climate dynamics of a hard snowball Earth. J. Geophys Res — Atmospheres. 110(D1) D01111 doi:10.1029/2004JD005162

    Also I’ve read a bit of your book from your web site and cannot wait to purchase the published version. Thanks for all your work.

    best regards


  44. 144
    Geoff Wexler says:

    Raypierre’s 2nd response; penultimate sentence. Is it possible to provide a reference please?

    [Response: I could point you to Kasting's paper on Early Venus, which actually covers the relevant physics, but the point I was making would not be understandable to most people since he doesn't make it explicit. Hate to be a stuck record here, but the only place I know that really discusses this particular issue clearly is Chapter 4 of Principles of Planetary Climate. Given Hansen's claims about a runaway being a "dead-cert" if we burn all the coal, I might try to work something about this into the NRC Carbon Stabilization report, but it's not at the heart of what we are trying to do there. I haven't written anything peer-reviewed about the effect of clouds on a runaway, but that's in the works for the next few years. --raypierre]

  45. 145
    Completely Fed Up says:

    “But when the ice started melting, wouldn’t that have caused a hellaceous hot house?”

    When ice melts, it goes to a liquid phase which isn’t a greenhouse gas…

    [Response: It does cause a helllaceous hothouse, not because of the liquid water, but because the melting ice gives you low albedo but you still have the high CO2. The land temperatures get pretty hellaceous, but the maximum ocean temperature stays around 320K. See the discussion in the EPSL paper by LeHir, Donnadieu and myself. I think I put a copy on my publication page on my web site. --raypierre]

  46. 146
    Completely Fed Up says:

    “I was trying to explain that I would like to see a minimal model that is not vulnerable to saturation arguements”

    Do you see the topic of this thread?

    Plass’ model doesn’t suffer from that problem.

  47. 147
    Hank Roberts says:

    > … But for some reason he has been keen on fusion power.
    Rich fantasy life.

  48. 148
    John E. Pearson says:

    146: Fed wrote: “Do you see the topic of this thread? Plass’ model doesn’t suffer from that problem.”

    So you claim that Plass’ model contains the minimum complexity required to understand the bare bones physics of global warming? The last time I tried to read that paper I found it really tough going and asked Gavin to explain it to me. IN fact I think that exchange might be where Gavin learned about Plass’ paper. IN any event, Plass’ paper is a hell of a long way from my idea of a minimal model. A minimal model is one in which if you get rid of any piece of the model the effect you’re modeling goes away. It’s been 3 years since I looked at Plass’ paper but I seem to recall that Plass considered the detailed absorption spectrum of CO2. That can’t possibly be needed to obtain the qualitative picture that I keep hearing. Physics is full of over idealized models two-level atoms etc. They’re useful. I keep hearing this simple explanation that doesn’t invoke anywhere near the level of complexity that Plass dealt with. That’s what I’m asking for. Has no one done this?

    [Response: There are all sorts of minimal models which people have done, depending on the use. If you want to connect climate change to a specific CO2 concentration, then the sort of detailed radiative physics in Plass is unavoidable. It can be boiled down to a simple statement that the effect of CO2 on the outgoing infrared radiation is logarithmic in CO2 concentration, but you can't derive that without the detailed spectrally resolved kind of calculation done by Plass. If you are only interested in a general calculation of how atmospheric infrared opacity, in conjunction with convection, increases the temperature of the surface, then the minimal model is the "all troposphere" grey model I discuss in about one page of Chapter 3 of Principles of Planetary Climate. It is elaborated more precisely in the discussion of the grey-gas all-troposphere model in Ch. 4. That reasoning has been discussed many places (including the first edition of Goody's radiation book which we repeated in the IPCC TAR), but an awful lot of textbooks are kind of mushy on these things. That's the frustration that led me to embark on writing Principles. --raypierre]

  49. 149

    109 Hank Roberts

    Ok, I use earth area as 5.1×10^14 m^2 and there are 6.3×10^8 seconds in 20 years so for .9 W/m^2, I get 2.89×10^23 Joules due to supposed .9 W/m^2 going into the oceans. This is about .3 times the 10×10^23 Joules indicated by the NOAA chart (see Dec 28, 09 post here at RC).

    So according to this, the world surface had to take in 3.46 times .9 W/m^2 over that twenty years, or about 3.1 W/m^2

    It seems that the heat that actually went into the ocean came from the heat in the atmosphere, and thus would reduce atmospheric temperature. The temperature data suggests that this should be the case.

    From raypierre’s statement in the article here posted, it sounds like the ocean part in bringing the system back into balance is ignored. Probably rahpierre was simplifying, and that is not the case, but it sounds like the prevailing consensus number is .9 W/m^2 and the data from NOAA now indicates that this is too low. I continue to wonder if the mechanism by which the ocean takes on heat is not adequately treated in the modeling.

    Raypierre’s statement that I refer to:
    ((exactly pasted)
    The way the greenhouse effect really works is that adding CO2 reduces the infrared out the top of the atmosphere, which means the planet receives more solar energy than it is getting rid of as infrared out the top. The only way to bring the system back into balance is for the whole troposphere to warm up. It is the corresponding warming of the low level air that drags the surface temperature along with it (end paste))

    124 Luke Silburn,

    Thanks for your help on this. Your answer agrees with mine if you use the whole earth area rather than just the ocean area. (I use earth area based on the old French definition of the meter where 10 million get you from equator to pole.) I think the climate modeling folk are referring to the whole earth surface when they talk about the .9 W/m^2 so the actual ocean has to work harder. According to my number of 3.1 W/m^2 for the whole earth, the actual rate into the ocean (2/3 of the earth surface) would need to be 1.33 times faster so it would be 4.7 W/m^2. Since NOAA was actually talking about ocean heat content, that would be the number to use, which is about same answer you came up with.

  50. 150
    John E. Pearson says:

    148: Cool. Err. Not what I meant. Thanks Ray Pierre! I’ll buy a copy when it comes out. I wasn’t after CO2 specific details. I was after “you put on a thicker blanket and you stay warmer” but unlike a real blanket we’re talking about a gas which sets its own height etc and instead of conduction it’s radiation etc. There’s a bunch of physics that goes into that simple statement and I’d like to know it. I look forward to your book.

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