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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. 1
    Chad says:

    Very well written post. I look forward to reading The Warming Papers.

  2. 2
    Geoff Wexler says:

    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.

    All too true. Try reading Sadie Carnot who nearly discovered the second law of thermodynamics before others established the first. Or the early theories of colour vision.

    (Congratulations about your book)

  3. 3

    When I read this article, I found the mention of Fox and Hedgehog baffling. I didn’t know what they were intended to represent.

    On going back to Gavin’s earlier post I have found out; and it might be useful to include in this post as well an explicit identification of where the metaphor arises. The relevant paragraph of the previous RC post is:

    Eli has described this using Isaiah Berlin’s Hedgehog and the Fox metaphor – Plass being the Hedgehog who knows one big thing, and for whom the details are more incidental. I think this is a reasonable take, as long as it is realised that Hedgehogs are not always right, even though in this case he was.

    PS. Raypierre, thank you for being so generous with the online drafts of your new book! It has been an enormous help to me through the year just past. I hope it is a huge success.

    [Response: My pleasure! And my thanks go out to all the many people who provided comments on the various drafts. I tried to include as many as I could track down in the acknowledgements, but I’m sure I’ve missed some, since I lost track of some of my back emails. –raypierre]

  4. 4
    CM says:

    Congratulations on the book, and thanks for sharing the online drafts. (But isn’t “animula” a tad diminutive for a 545-page brick?)

    [Response: More like a 700 page brick, once the problems were merged in and the index done. –raypierre]

  5. 5
    Terry Aust says:

    off topic, but I would really appreciate a modern view of how Calledar handled the data to recognise global warming from the temperature data so far ahead of anyone else. Is such a discussion in ‘The Warming Papers’

    [Response: We edited the very long Callendar paper some, but that is discussed in The Warming Papers. –raypierre]

  6. 6

    I’d like to add my thanks for this discussion. There seems to be an interesting back-and-forth pattern to the development of the conceptual framework of the atmospheric mechanics of the greenhouse effect: I was startled to find this description by Ekholm in his 1901 paper:

    . . . radiation from the earth into space does not go directly from the ground, but on the average from a layer of the atmosphere having a considerable height above sea-level. . . The greater is the absorbing power of the air for heat rays emitted from the ground, the higher will that layer be. But the higher the layer, the lower is its temperature relatively to the ground; and as the radiation from the layer into space is the less the lower its temperature is, it follows that the ground will be hotter the higher the radiating layer is.

    (Of course, given the close association between Ekholm and Arrhenius, it’s logical that they would have shared a conceptual framework.) It’s been suggested that this mode of warming is also implicit even in Tyndall’s well-known “dam” analogy of the effect of CO2 in the atmosphere.

    On the other hand, if I read it correctly, Guy Callendar’s 1938 paper “The Artificial Production Of Carbon Dioxide And Its Effect On Temperature,” considers warming purely from the perspective of downwelling IR–his discussion is even titled “Sky Radiation.” He cites Angstrom and several others on this. Perhaps Plass was following this (then) more modern “thread”–although Plass does not mention Callendar in the Introduction (where he does cite Tyndall, T.C. Chamberlain, and Arrhenius), “The Artificial Production Of CO2″ does appear in the bibliography.

    Callendar’s paper is here:

    http://www.rmets.org/pdf/qjcallender38.pdf

  7. 7
    Theo Hopkins says:

    Hedgehog and foxes?

    Got me baffled, too.

    Is it a US (not UK) expression?

  8. 8
    Frank Giger says:

    Winky smiley Internet thingy:

    So with heat radiating into space by layer, with subsequent cooling as one gains into the atmosphere being better understood, has the most probable altitude of Icarus’ demise be determined?

    Also, best picture of a hedgehog ever.

  9. 9
    CM says:

    Re: The hedgehog and the fox

    > Is it a US (not UK expression)?

    Classical Greek. Archilochus, 7th century BC: “The fox knows many things, the hedgehog knows one great thing.” Sir Isaiah Berlin (your side of the pond) wrote a popular book of intellectual history by that title.

  10. 10
    Kate Cell says:

    “The Hedgehog and the Fox” is an essay by the liberal philosopher Isaiah Berlin. The title is a reference to a fragment attributed to the ancient Greek poet Archilochus: πόλλ’ οἶδ’ ἀλώπηξ, ἀλλ’ ἐχῖνος ἓν μέγα. (“The fox knows many things, but the hedgehog knows one big thing”).

    http://en.wikipedia.org/wiki/The_Hedgehog_and_the_Fox

  11. 11
    Ron Taylor says:

    “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 …”

    Thank you Ray. That is the clearest, most concise explanation of the effect of CO2 I have ever read.

  12. 12
    Steve Milesworthy says:

    I imagine it is quite a banal thing to measure, but has anyone measured the spectrum of back radiation in a dry atmosphere to show the CO2 emission? Even better, to show it change with concentration. i.e. a reverse version of the following paper which compared outgoing longwave spectra:

    Harries J., H. Brindley, P. Sagoo, and R. Bantges, 2001: Increases in greenhouse forcing inferred from the outgoing longwave spectra of the Earth in 1970 and 1997. Nature, 410, 355–357

    It’s to provide an additional answer to the perennial “I want experimental proof of CO2″ demand.

    [Response: Dan Lubin and others have several papers documenting the downwelling infrared spectrum, using an FTIR instrument. The problem is finding a dry place. Most of the tropical results show a lot of water vapor effect in addition to CO2. The best bet for getting a clean CO2 spectrum would be on a clear night in the Antarctic winter, but most of Dan’s Antarctic results seem to focus on cloud effects (which are less banal). I haven’t found exactly what you’re looking for. On the other hand, if you google “AIRS spectra” you’ll find a certain number of new analyses of the top of atmosphere spectra, which clearly show the CO2 feature. That’s even more valuable as proof of the validity of our understanding of the CO2 radiative effect. It’s not a long enough time series to detect trends in the CO2 feature, though, and doing that is not a high scientific priority in comparison to things that would shed light on water vapor or (especially) cloud feedbacks. –raypierre]

  13. 13
    Jim Bouldin says:

    Great article, thank you!

  14. 14
    Eli Rabett says:

    Wonderful essay, and many thanks for the book.

    I’ll take the liberty of adding a codicil, The fox knows many things, but the hedgehog knows one big thing. If it’s wrong, the hedgehog is a crank.

  15. 15
    Icarus says:

    How reliable and detailed are our measurements of top-of-atmosphere energy budget? Can we say for certain that the Earth has been consistently receiving more energy than it radiates away to space in recent years or decades? If so, that would surely invalidate all arguments about a pause or reversal of global warming at a stroke. Everyone can easily see that if more heat is being put into the climate system than is being lost to space, the planet *has* to be warming up, regardless of any natural fluctuations in surface temperature due to heat moving around in ocean currents, or melting of icecaps, or any other mechanism.

    [Response: The satellite TOA budgets are not yet accurate enough to do this sort of thing, or at least not stable enough over time. Hansen argues that monitoring the ocean heat storage is a more feasible way to get at the same issue, since the atmosphere itself comes into equilibrium quickly, so that most of the TOA imbalance is reflected in changes in the ocean heat storage. There are plans for operational monitoring of the TOA budget over the coming decades, but I am still somewhat concerned that this may not be done with enough accuracy to adequately track the behavior of cloud and water vapor feedbacks. –raypierre]

  16. 16
    Todd Albert says:

    “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.”

    Wonderful!

    Looking forward to “The Warming Papers” and “Principles of Planetary Climate” (perhaps a new text for my Climatology class in Fall).

  17. 17
    Eli Rabett says:

    There is a nice illustration of how the level at which the IR emission reaches space for different CO2 concentrations on Rabett Run (Ray contributed to the discussion earlier)

  18. 18
    Hank Roberts says:

    For those who like me need to look up the other classical reference:
    http://tomclarkblog.blogspot.com/2009/03/animula-vagula-blandula.html

  19. 19
    Phil. Felton says:

    CM says:
    13 January 2010 at 8:02 AM
    Congratulations on the book, and thanks for sharing the online drafts. (But isn’t “animula” a tad diminutive for a 545-page brick?)

    You shouldn’t take these analogies too literally, after all I doubt whether Raypierre is implying that Cambridge is a barren place (loca pallidula rigida nudula).

  20. 20
    Timothy Chase says:

    raypierre,

    I have a Windows machine, System 7 with Sun virtual machine with Ubuntu (a version of Linux) installed, and of course it is easy enough to download Python. Do you have a prepackage of the software that goes along with your book yet for Linux? Shouldn’t be a problem getting it to run in the virtual machine — I believe.

    [Response: I’m still cleaning up the software before the final release, but it works find under Linux. In fact, it’s only the graphics that is a bit machine-dependent, but versions of that will work on any machine
    that has x11. (and most of the software can still be run even without graphics, though the graphics is nice to have). The
    Python uses numpy, but that’s included with most Python distributions these days. For some machines, it may be necessary to recompile the NCAR radiation package in order to make use of the python radiation interface, but I’m providing ready made builds for OS X and Linux. I haven’t yet tried building the NCAR package and Python interface on Windows, but that will come at some point. –raypierre]

  21. 21
    Timothy Chase says:

    Kate Cell wrote in 10:

    “The Hedgehog and the Fox” is an essay by the liberal philosopher Isaiah Berlin. The title is a reference to a fragment attributed to the ancient Greek poet Archilochus: πόλλ’ οἶδ’ ἀλώπηξ, ἀλλ’ ἐχῖνος ἓν μέγα. (“The fox knows many things, but the hedgehog knows one big thing”).

    I figure the Hedgehog had Asperger’s syndrome and the Fox was bipolar.

    This would explain why the Fox could see things from a variety of perspectives. Undoubtedly had grandiose plans but kept coming up with some new grandiose plan before he had the chance to finish the previous one. Ah, but the Hedgehog — he had the benefit of his tunnel vision!

  22. 22
    Lance Olsen says:

    Raypierre
    I doubt very much that you missed these 2 early researchers in preparing your book, but others here may appreciate learning of their thinking, as described in the following 2 letters to Nature.

    NATURE
    Vol 448
    August 30, 2007

    CORRESPONDENCE

    Climate: Sawyer predicted rate of warming in 1972

    SIR – Thirty-five years ago this week, Nature published a paper titled ‘Man-made carbon dioxide and the “greenhouse” effect’ by the eminent atmospheric scientist J. S. Sawyer (Nature 239, 23-26; 1972). In four pages Sawyer summarized what was known about the role of carbon dioxide in enhancing the natural greenhouse effect, and made a remarkable prediction of the warming expected at the end of the twentieth century. He concluded that the 25% increase in atmospheric carbon dioxide predicted to occur by 2000 corresponded to an increase of 0.6 °C in world temperature.

    In fact the global surface temperature rose about 0.5 °C between the early 1970s and 2000. Considering that global temperatures had, if anything, been falling in the decades leading up to the early 1970s, Sawyer’s prediction of a reversal of this trend, and of the correct magnitude of the warming, is perhaps the most remarkable long-range forecast ever made.

    Sawyer’s review built on the work of many other scientists, including John Tyndall’s in the nineteenth century (see, for example, J. Tyndall Philos. Mag. 22, 169-194 and 273-285; 1861) and Guy Callender’s in the mid-twentieth (for example, G. S. Callendar, Weather 4, 310-314; 1949). But the anniversary of his paper is a reminder that, far from being a modern preoccupation, the effects of carbon dioxide on the global climate have been recognized for many decades.

    Today, improved data, models and analyses allow discussion of possible changes in numerous meteorological variables aside from those Sawyer described. Hosting such discussions, the four volumes of the Intergovernmental Panel on Climate Change 2007 assessment run to several thousand pages, with more than 400 authors and about 2,500 reviewers. Despite huge efforts, and advances in the science, the scientific consensus on the amount of global warming expected from increasing atmospheric carbon dioxide concentrations has changed little from that in Sawyer’s time.

    Neville Nicholls
    School of Geography and Environmental Science,
    Monash University, Victoria 3800, Australia

    —————————————————
    Fires and climate linked in nineteenth century

    SIR – ‘Atmospheric brown clouds’, resulting from the burning of fossil fuels and biomass, have recently been reported to have a large effect on climate by altering the atmosphere’s absorption of solar radiation (V. Ramanathan et al. Nature 448, 575-578; 2007).

    Interestingly, even in the nineteenth century, some scientists held the view that tiny particles, or aerosols, produced from burning affect solar radiation, clouds and precipitation on a large scale – all factors that play into climate. One of them, German geographer Alexander Freiherr von Danckelman, wrote an insightful but little-noticed paper on the topic (A. von Danckelman Z. österr. Ges. Met. (Meteorol. Z.) 19, 301-311; 1884).

    After observing huge savannah fires in Africa during the 1880s, von Danckelman reported that fires were accompanied by cumulus clouds, which subsequently spread and thinned, forming a brownish or blueish haze that persisted for days to weeks. He argued against the view that fires were an immediate cause of rain showers, and proposed instead that they affected cloudiness and precipitation in an “indirect way”. He realized that by providing cloud condensation nuclei, fires might contribute to the fog and drizzle typical of the dry season. Estimating the amount of biomass burned in Africa each year, he concluded that savannah fires must have a major influence on large-scale climate.

    Von Danckelman’s descriptions of haze produced from burning biomass and its effects on climate are surprisingly accurate. Although not every detail is correct, his theories anticipated many aspects of the current discussion on biomass burning and the effects of aerosols. Sadly his work, published in French and German, is almost forgotten today and references to his papers are absent in current studies.

    Stefan Brönnimann
    Institute for Atmospheric and Climate Science,
    ETH Zurich, Universitätsstraße 16,
    CH-8092 Zürich, Switzerland

  23. 23
    Doug Bostrom says:

    What an excellent essay. On a recent thread there was some discussion here about evaporation serving as a dependable limit on surface temperature, an idea which is incomplete unless one follows the budget into space. This piece is a great reminder about the limitations of focusing too much on what’s going on at the bottom of the atmosphere. Thank you!

  24. 24
    James Staples says:

    Thanks for pointing out the differences in what Plass said, and the total reality of things; perhaps this misconception is one of the reasons I’ve seen so many people indicate that they think CO2 acts like some kind of a ‘magnifying glass’ – rather than a down comforter!
    BTW: I learned of Gavins piece because I read American Scientist (just learned they, like Robert Oppenheimer, were investigated as ‘pinkos’ by Sen. McCarthy in the 1950’s – which makes me love them even more; and doesn’t history truly repeat itself?); I suggest that anyone interested look into the Dec. 2009 Issue – it has a complete reprint of Plass original Item, as well as a nice Chronology of his predicesors who made the ‘other’ discoveries that made Plass’ discoveries possible.

  25. 25
    Jeffrey Davis says:

    The hedgehog expression has become a fixture in this country recently, but the first time I recall it was as apologia for Ronald Reagan’s political thinking. I suspect the expression has grown recently due to the hagiography of Reagan during the 2008 election.

  26. 26
    Geoff Wexler says:

    Re: #12

    has anyone measured the spectrum of back radiation in a dry atmosphere

    Start with

    http://www.skepticalscience.com/empirical-evidence-for-co2-enhanced-greenhouse-effect.htm

    and scroll down to
    “Surface measurements of downward longwave radiation”

  27. 27
    Edward Greisch says:

    15 Icarus: NASA satellites have been measuring the infrared radiation leaving Earth for quite some time. Denialists never check with NASA. Somebody else, the real RC people surely know more about this than I do. Perhaps NASA satellites would be a good subject for a post?

    Thanks, raypierre. That clears up a lot of things, including that hedgehogs have short quills. Porcupines have much longer quills.

  28. 28
    Jim Roland says:

    There is only one “s” in Zeus. Perhaps you were confusing him with “Seuss”?

    [Response: Ack, I must have had Revelle and Zeuss on the brain –raypierre]

  29. 29

    Kate, don’t you have the wrong breath mark on “hen?”

  30. 30
    Ralph says:

    The CO2 v. temperature relationship is sometimes mentioned in degrees warming for a doubling of CO2. That suggests a logarithmic relationship, which I find counter-intuitive; anyone care to explain that to me?

    [Response: The logarithmic relationship is between CO2 concentrations and the forcing and it is something that has been known for decades (if not back to the 19th Century). The dependence arises because of the way that the absorption near the peak spectral line changes as CO2 changes. The consequence is that the forcing for each successive doubling is roughly the same at least up to around 1000ppm, and down to maybe 50 (?) ppm. For much smaller amounts the relationship is linear. – gavin]

  31. 31

    I now have references for both the predictions and the confirmations for 11 of the 17 climate modeling successes on my web page. I don’t want to put up the reference list until I have citations for ALL the items mentioned. If anyone can find citations from the peer-reviewed science literature either predicting the following, or confirming it later, please email me or post here:

    * Ozone hole effect on southern ocean winds
    * Hadley Cells expand
    * Storm tracks move poleward
    * Tropopause and radiating altitude rise
    * Tropical “super greenhouse effect”
    * Expanded range of hurricanes and cyclones

    I’m paging through Google Scholar, but haven’t found anything I can clearly interpret well enough to cite confidently yet.

  32. 32
    Bill says:

    let me try again [edit – OT and ill-posed]

  33. 33

    Thanks for this explanation by raypierre. It is helpful though my understanding of the radiative heat transfer processes continues to be a bit vague.

    However, the lines, “—-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 —,” suggest that other ways for the surface temperature to lag the temperature equilibrium at the top of the atmosphere might also be relevant. At the surface of the world’s oceans we then should count the heat taken from the surface and transported downward. Where there is wind, therefore waves, there is a vertical current component and therefore a vertical heat transfer. This seems to be something that would be a substantial on-going flow effect, varying of course with wind. Thus whatever wind increase occurred due to surface heating should increase vertical heat movement downward. My point continues to be that ocean heat content will increase instead of surface heat content, ie. surface temperature. And though the globe will be warmed just the same, arguments about surface temperature increase are not too meaningful.

    I had previously thought that the radiative equilibrium was for surface temperature and thus it was hard to see how the heat into the oceans would change things by much, since the control of that surface temperature would be mostly governed by the equilibrium requirement.

  34. 34
    Bill says:

    My previous question is clearly related to this thread:#15, 17, 30 as examples. How do we establish baselines for change???

    [Response: Your question was not relevant. There is no ‘optimum’ temperature as has been discussed hundreds of times. This has nothing to do with Plass, surface energy balances or CO2 forcing. It is OT. – gavin]

  35. 35
    CM says:

    BPL (#31),
    this should be the right thread to get a reference for “radiating altitude rise”…

    For the less on-topic “ozone hole effect on southern ocean winds”, I thought of Thompson & Solomon (2002) who refer to three simulations with greenhouse gases/ozone loss giving same-sign trends in the Southern Annular Mode as their observations: Fyfe et al. (1999), Kushner et al. (2001), and Sexton et al. (2001). Amateur hunch, needs careful vetting.

  36. 36
    Chris Colose says:

    Good article. Hopefully raypierre will be around more now that the book is finished.

    This is one of the problems I have with the simple layer model as it is introduced in some textbooks, such as Dennis Hartmann’s or David Archer’s “Understanding the Forecast.” This is where you simply add up the influence from successive blackbody “layers” with a final result of something that usually ends up looking like T_s=T_eff*(N+1)^0.25, where N is the number of layers, and T_s and T_eff are the surface and effective temperatures, respectively. Archer discusses some of the incompleteness of this model in his class lectures (lack of convection, layers are not fully transparent in the shortwave nor fully opaque in the longwave) but I think the whole presentation misses the point completely. It has absolutely no top-of-atmosphere perspective. In fact, if one were to set up the “layer model” with a bunch of layers at the same temperature (i.e., an isothermal atmosphere), the result would be a surface temperature that could be much greater than the temperature achieved by radiation balance with the sun, when in reality, you cannot get a greenhouse effect in such a situation.

    By the way, for the people new to RC, raypierre has an older article on the same subject which pointed out some of the misunderstandings of the surface energy budget that actually showed up in the primary literature (http://www.realclimate.org/index.php/archives/2005/11/busy-week-for-water-vapor/)

  37. 37

    Raypierre, a book collecting the classic papers is a brilliant idea – I shall look forward to reading it. But who is your target audience? Would it work as an introductory undergrad text? Or grad school only? I imagine the papers themselves might be pretty tough going for the non-speciallist, but who did you aim your commentaries at?

    [Response: The essays are meant to be accessible to the undergraduate audience or scientifically literate layperson, though certainly more advanced researchers may also be interested in the historical perspective. Some parts of a few of the papers (the QJRMS one by Plass in particular) would be heavy going for an undergrad audience, but most of the papers are very accessible to readers without an extensive technical background. Where they aren’t, the essays are meant to help along. –raypierre]

  38. 38
    Jerry Steffens says:

    #33

    “My point continues to be that ocean heat content will increase instead of surface heat content, ie. surface temperature.”

    Uh, 70% of the earth’s surface is ocean. Plus, there is a rather vigorous exchange of energy between the ocean and atmosphere.

  39. 39
    Jerry Steffens says:

    One problem with using a surface-radiation argument to explain surface warming is that it is difficult to answer the question, “Where does the extra energy come from?”. (Why should the act of adding extra molecules of certain gases create energy?) In a top-of-the-atmosphere argument, there is no such problem:The source of energy is the temporary excess of absorbed solar radiation over outgoing longwave radiation, as explained in this post.

    [Response: Yes that’s very true. The surface budget represents an exchange between the ocean or land heat reservoir and the atmosphere. If one gains heat the other loses. –raypierre]

  40. 40
    Hank Roberts says:

    > Jerry Steffens 13 January 2010 at 5:14 PM

    Here, perhaps a picture will help you understand where the energy is coming from and going and how much:

    http://chriscolose.files.wordpress.com/2008/12/kiehl4.jpg?w=480&h=350

  41. 41
    Hank Roberts says:

    Further for Jerry Steffens:

    Let me suggest a paraphrase that might help:

    > it is difficult to answer the question, “Where does the
    > extra energy come from?”. (Why should the act of adding
    > an extra blanket on the bed on a cold night create energy?)

  42. 42
    donald moore says:

    I have just received an e-mail blog from nasa re. grace satellite measurements show antarctica is loosing ice at an accellerated rate.I would suggest an exponential rate since there are many aspects of climate change that are accelerating the acceleration and this is something that computer modeling cannot project,rather like shutting the door after the horse has bolted.If we need to have evidence of what will happen when warmerlattitudes get warmer and meet colder lattitudes getting colder[like an ice cube melting in a glass of water]we need look no further than the coast of labrador which has 60% of the year fog[low level cloud]due to melting ice meeting warm gulf stream water.GET MORE FOXY and less of a hedgehog.

  43. 43
    Robert says:

    Another left-wing nut commits intellectual suicide.

    http://www.augustreview.com/news_commentary/general/exposing_the_global_warming_lie__20091212153/

    [Response: That may have happened a while ago…. – gavin]

  44. 44
    Noel Fuller says:

    I have read this essay and the comments with great interest but I am always drawn on matters of foxes and hedgehogs – they represent phase shifts within an evolutionary process. A fox may become a hedgehog, but then discover that the one big thing is yet another thing. Hedgehogs, as just inferred, very reluctantly evolve into foxes, and so on ad infinitum! :)

  45. 45
    Andrew says:

    @Robert: “43.Another left-wing nut commits intellectual suicide.”

    How is that guy on the left-wing? He quotes the Heritage Foundation pretty freely for someone on the left wing. Then he was a paper industry forester.

    I’m just not seeing the left-wing credential. Did I miss something?

  46. 46
    Alexandre says:

    Barton Paul Levenson #31

    About the “Hadley Cells expand”: I think this may help.

    Fu 2006
    Enhanced Mid-Latitude Tropospheric Warming in Satellite Measurements
    http://www.sciencemag.org/cgi/content/abstract/312/5777/1179

    It mentions a “pattern indicative of a widening of the tropical circulation and a poleward shift of the tropospheric jet streams”.

    BTW, I´ve been trying to do a “AGW basic math” myself – yours is great, but I´m aiming for something with less parameterization (and less impressive results). Do you know any online source for an IR absorption coefficient table of CO2?

  47. 47
    Ray Ladbury says:

    Robert says, “Another left-wing nut commits intellectual suicide.”

    Left wing? Uh, dude, that site is a LaRouche organ–you know, the guy who called Ronald Reagan an “unwitting communist stooge?”

  48. 48
    Jerry Steffens says:

    #40,#41 (Hank)

    My comment in #38 was based upon my experience in the classroom, having taught climate change at the university level for almost 20 years. (The question concerning the source of energy is one that a student might well ask.) I was simply pointing out one reason why an explanation in terms of top-of-the-atmosphere radiation fluxes is pedagogically superior to one involving surface fluxes.

    By the way, I don’t think that your comment in #41 is a particularly good analogy — in your example, the source of energy is INTERNAL(body heat), whereas the source of energy for the earth-atmosphere system is EXTERNAL. A sharp student would be sure to point that out.

  49. 49
    Eli Rabett says:

    The short answer to the question of where the energy comes to warm the surface is from energy that left the surface but was turned around by backradiation. Without the greenhouse gases it would just keep going

  50. 50
    Doug Bostrom says:

    Ray Ladbury says: 13 January 2010 at 8:27 PM

    Anyway, who cares? Wrong is wrong.


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