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  1. Excellent article! I have been seeing the “saturation” argument a fair amount recently, and this is a nice summary of why it’s not true. Thanks for posting.

    Comment by Barton Paul Levenson — 26 Jun 2007 @ 7:41 AM

  2. Thank you very much realclimate.

    Top stuff.

    Any idea what levels of CO2 required would cause saturation ?

    Comment by pete best — 26 Jun 2007 @ 7:50 AM

  3. I used an excerpt from this realclimate article – which I put at the bottom of my recent article at Newsvine called: 15 cartoon finalists on science, policy and climate change, at:

    http://npat.newsvine.com/_news/2007/06/25/802021-15-cartoon-finalists-on-science-policy-and-climate-change

    Comment by pat n — 26 Jun 2007 @ 8:58 AM

  4. Any idea what levels of CO2 required would cause saturation ?

    Looking at the graph on the Part II article it looks like there is still extra areas to absorb at 100,000 times pre-industrial CO2 levels, up at the 21-22 micron wavelengths, and some down at 11.5 microns or so that would take 10,000 times as much to be absorbed at the other end of the peak. It seems unlikely there is enough carbon around for us to burn to get it that high, so in practise we aren’t going to reach saturation at any point.

    [Response: Quite true. In fact, you need to look in the spectrum beyond the graph in Part II to see when CO2 really gets saturated, because the portions of the spectrum outside the wavelength range shown can be considered transparent to thermal infrared for the purposes of discussing Earth, but start to absorb significantly at extremely high CO2 values like those on Venus. Of particular interest in this regard is the CO2 continuum, which starts just to the shortwave side of the graph in Part II. When you take the CO2 continuum into account you find that for gravity like Earth or Venus, CO2 starts to become saturated for a surface pressure of about 10 bars (10 Earth atmospheres). Venus has a surface pressure of about 90 bars, and has an almost pure CO2 atmosphere. Even for Venus, to infer that CO2 absorption is saturated one needs to go to absorption data beyond what's in the HITRAN database, since the high surface temperature causes the surface of the planet to radiate into shorter wave parts of the infrared than does Earth. On Earth, both the lack of saturation and the "thinning and cooling" argument come into play in determining the climate. Venus is an example of a planet that can be considered saturated in the sense imagined by Angstrom for Earth, but which nevertheless gets warmer as you add additional CO2 because of the "thinning and cooling" argument. --raypierre]

    Comment by stuart — 26 Jun 2007 @ 9:18 AM

  5. Well done.

    This article makes the physics involved relatively easy to understand, without oversimplifying. It also clearly explains why the current crop of saturation “arguments” out there are irrelevant. It nicely ties together the science with the relevant history, which I find fascinating. Finally, it summarizes the main points of the article in a concise closing paragraph.

    5 stars.

    Comment by BCC — 26 Jun 2007 @ 9:30 AM

  6. If I am reading this correctly (and I may not be), as co2 concentration rise, the greenhouse effect shifts somewhat to the upper atmosphere where water vapor is nearly absent and co2 has a larger relative effect. Two questions. First, why then do model predictions and actual measurements show the troposhere warming and the stratosphere cooling? Second, the infra red absorption rate is proportional to the number of molecules of co2 encountered by the radiation. With co2 well dispersed in the entire column of the atmosphere at 380 ppm, are not there many fewer co2 molecules in the thin air of the stratosphere and therefore limited absorption of radiation?

    [Response: You are reading this correctly, though you should keep in mind that the level which controls the greenhouse effect depends on which wavelength you are looking at (see Part II). Near the centers of strong absorption lines, even the stratosphere by itself is strongly absorbing, and hence (by something known as Kirchoff's Law) strongly emitting. The reason the stratosphere cools upon increase of CO2 is that the balance in the stratosphere is between absorption of solar radiation by ozone and cooling by infrared emission. As you increase the CO2, there is excessive radiative cooling, so the stratosphere has to cool down to come back into balance. As for your second question, it is precisely because there are fewer molecules of CO2 in the thin upper air that CO2 increases continue to increase the greenhouse effect even when the column as a whole is saturated. Because you are adding more molecules throughout the column, the extra molecules you add at high layers where there isn't initially enough CO2 to absorb everything can make a difference. --raypierre]

    Comment by B Buckner — 26 Jun 2007 @ 9:43 AM

  7. Of potential interest to people here, I recently completed making a figure showing atmospheric absorption bands for the principle gases. The primary goal of the figure was to compare downgoing solar and upgoing thermal radiation, so it doesn’t do much to clarify the saturation arguments per se, but does show the relative importance of water vapor and other gases and help understand where the saturation arguments are coming from.

    Though not really a complete argument, for unsophisticated audiences, I find that saying that more CO2 allows heat to be held “closer” to the Earth’s surface is often an effective response to the saturation line of thought.

    Comment by Robert A. Rohde — 26 Jun 2007 @ 10:32 AM

  8. All of this is greatly appreciated – including the links. Undoubtedly it will take a while for me to absorb (absorp?) all I can from the light with which you both (and David Archer) have illuminated this subject, but that means a journey of discovery which I will enjoy for quite some time to come.

    Comment by Timothy Chase — 26 Jun 2007 @ 11:13 AM

  9. Even if rising CO2 levels were not a global warming concern, there is another reason to be concerned about rising CO2: toxicity. Humans evolved in conditions of pre-industrial CO2 levels, so presumably we tolerate 300 ppm just fine, but the physiological effects of higher CO2 levels on a long-term basis have perhaps not been adequately studied. Do you feel a little drowsey sitting in the auditorium or class room? It may well be related to higher CO2 levels – upwards of 600 ppm would not be unusual. Levels as low as 2000 ppm may result in unconsciousness, but lower levels may result in impairment in our mental functions and have other health implications.

    Comment by Gene Hawkridge — 26 Jun 2007 @ 11:44 AM

  10. Re Raypierre’s response to 4

    It would help clarify matters further to point out that because the peak wavelength of a planet’s radiated energy depends on the fourth power of its temperature , absorption at 20 micron wavelengths is much less important on Earth than absorption around 10 microns , for having a temperature of roughly 300K, Earth is essentially a ten micron peak black body.

    The 21-22 micron CO2 band corresponds to a blackbody temperature of ~150 Kelvin, too low to be of much Earthly interest because of the feeble radiated power. In the outer solar system many bodies have even lower temperatures, but CO2′s gaseous absorption spectrum is moot because it freezes out around 200K.

    It would be great if RealClimate could persuade Weart to apply his clear-eyed prose to _An Inconvenient Truth_ with the same vigor he devoted to hyperbolic Cold War icons in his superb book _Nuclear Fear : A History Of Images’_

    [Response: You're quite wrong about much of what you've said in this comment. For one thing, you're confusing the Stefan-Boltzman law with the Wien displacement law; the wavelength of peak emission is inversely proportional to the temperature itself, not to the fourth power of the temperature. Further, because of the Planck law, the emission tails off very sharply at wavelengths shorter than the peak, but only rather gradually at wavelengths longer than the peak. For that reason, the emission of the Earth at wavelengths where CO2 is a good absorber is extremely important. You'd understand this if you had bothered to play around with Dave Archer's online spectrally resolved model. Really, you are rather ignorant for one who makes pronouncements of this sort with such confidence. I won't even get into how your prejudice against Al Gore blinds you to the essential correctness of what he presents in "An Inconvenient Truth." And please, let's not get into any further discussion of either Al Gore or nuclear weapons or nuclear power in this thread. Any such discussion will be considered off-topic and will be expunged. --raypierre]

    Comment by Russell Seitz — 26 Jun 2007 @ 11:57 AM

  11. Here is an explanation as to why, 17 years after global greenhouse warming was acknowledged as ‘real’, it is necessary to have RC to point out the lies and distortions of ‘skeptics’ and bogus scientists.

    http://www.motherjones.com/mojoblog/archives/2007/06/4723_cheney_stovepip.html

    Comment by catman306 — 26 Jun 2007 @ 12:43 PM

  12. That link doesn’t explain why there were only a few scientists in government who took an honest stand on climate change.

    Comment by pat n — 26 Jun 2007 @ 1:42 PM

  13. Are you assuming that CO2 concentrations are consistent (evenly distributed) throughout the vertical entirety of the atmosphere? It seems to me (based purely on intuition) that CO2 concentrations would be decreasingly significant with altitude, such that the top-most layers of the atmosphere would experience very little change in CO2 concentration. How much of the CO2 in the atmosphere actually exists up there? What percentage of all CO2 exists in the stratosphere?

    Comment by DaveS — 26 Jun 2007 @ 1:58 PM

  14. DaveS (#13) wrote:

    Are you assuming that CO2 concentrations are consistent (evenly distributed) throughout the vertical entirety of the atmosphere? It seems to me (based purely on intuition) that CO2 concentrations would be decreasingly significant with altitude, such that the top-most layers of the atmosphere would experience very little change in CO2 concentration. How much of the CO2 in the atmosphere actually exists up there? What percentage of all CO2 exists in the stratosphere?

    I don’t have the figures, and no doubt it differs by latitude, but you are right: the carbon dioxide isn’t evenly distributed.

    The marked decrease of the CO2 concentration in the lower stratosphere compared with the upper troposphere suggests that, contrary to previous practice, it is wrong to assume a constant mixing-ratio of CO2 in the troposphere and stratosphere.

    Concentration of CO2 in the Upper Troposphere and Lower Stratosphere (abstract)
    H. W. GEORGII & D. JOST
    Nature 221, 1040 (15 March 1969)
    http://www.nature.com/nature/journal/v221/n5185/abs/2211040a0.html

    The concentration is higher in the stratosphere. And we have known this since 1969.

    Comment by Timothy Chase — 26 Jun 2007 @ 2:33 PM

  15. The following is the citation to a recent peer reviewed study on the effects of CO2 enrichment and depletion upon cucumber growth in a greenhouse environment. I hope that your readers and scientists will comment on it. It appears that CO2 is a powerful gaseous fertilizer. Reduced CO2 diminishes plant growth. What will happen to the world’s food production capacity if CO2 levels are reduced below current levels?

    [Response: That's hardly likely... - gavin]

    Segura, M.L., Parra, J.F., Lorenzo, P., Sánchez-Guerrero, M.C. and Medrano, E. 2001. THE EFFECTS OF CO2 ENRICHMENT ON CUCUMBER GROWTH UNDER GREENHOUSE CONDITIONS. Acta Hort. (ISHS) 559:217-222
    http://www.actahort.org/books/559/559_31.htm

    Comment by W F Lenihan — 26 Jun 2007 @ 3:22 PM

  16. Re # 15 “What will happen to the world’s food production capacity if CO2 levels are reduced below current levels?

    Well, cucumbers have apparently been cultivated for some 3000 years (http://www.foodreference.com/html/a-cukes-history.html), so I’m willing to bet they would do just as well as they did at pre-industrial revolution levels of CO2. But, I doubt we will return to those lower levels any time soon.

    In the mean time, as CO2 levels continue to rise, poison ivy will also thrive (http://www.sciencenews.org/articles/20060603/fob1.asp). More cucumbers and poison ivy – it doesn’t get much better than that!

    Comment by Chuck Booth — 26 Jun 2007 @ 3:49 PM

  17. Off-topic, but the ‘Review comments and responses’ of IPCC WG1 AR4 are now on line. A fascinating read:

    http://ipcc-wg1.ucar.edu/wg1/Comments/wg1-commentFrameset.html

    Comment by PHE — 26 Jun 2007 @ 4:01 PM

  18. Perhaps readers would care to use this post to critique Steven Milloy’s recent statement on Fox News:

    “Based on the physics of the greenhouse effect, a doubling of carbon dioxide levels from the pre-industrial period (supposedly around 280 parts per million) to 560 parts per million (about 48 percent higher than present levels), might lead to an increase in average global temperature on the order of less than 1 degree centigrade – and we’ve already experienced about 60 percent of that increase.”

    “A further doubling of atmospheric carbon dioxide to 1,120 parts per million would result in even less of an increase in temperature because of the energy absorption properties of carbon dioxide.”

    “Essentially, the Earth only radiates so much energy back into the atmosphere that is available to be absorbed by carbon dioxide. Once all that energy is absorbed, superfluous carbon dioxide will not add to the greenhouse effect.”

    Briefly, the equilibrium climate sensitivity is estimated to be around 3C, not ‘less than 1C’, and could be higher (1.7-4.5 are the current 95% confidence limits). If it is 3C, than we’ve only experienced 20% of the estimated warming over the pre-industrial case. The second paragraph is just wrong – doubling CO2 from preindustrial to 2X should have the same temperature effect as going from 2X to 4X. However, you could see accelerating CO2 emissions leading to a faster rate of temperature increase due to carbon cycle-feedback effects. The third paragraph? This article deals with that.

    Why can’t ‘science journalists’ get their facts straight? Why does Fox hire ex-tobacco lobby employees to write articles claiming that global warming is a hoax?

    [Response: Under no definition is Milloy a 'science journalist'. On the contrary, science journalists generally do a pretty good job (and I've dealt with a lot). - gavin]

    Comment by Ike Solem — 26 Jun 2007 @ 4:17 PM

  19. Regarding Steve Milloy (#18):

    I thought it was more like 1.2 C for CO2 doubling – and that is before the water vapor feedback which would bring it up to 2.9 C.

    Perhaps Steve is trying to land a job at Exxon?

    Comment by Timothy Chase — 26 Jun 2007 @ 4:55 PM

  20. In support of real science journalists:
    Ten predictions about climate change that have come true, Tim Flannery, TO June 2007

    and Coastal zones set agenda on climate, Mike Lee, SDUT, Jun 2007

    On the minus side, Gloom and Doom in a a Sunny Day, by Emily Yoffe, WP is worth looking at. This is not really science journalism, but rather opinion. “I, however, refuse to see the apocalypse in every balmy day…”

    Here we have no mention of science, just an appeal to be ‘free from fear’ and a condemnation of the use of ‘the politics of fear’ by ‘global warming activists’.

    However, few if any of the science journalists who discuss climate change and global warming ever make the connection to renewable energy. Articles on global warming focus on the need to reduce emissions of to sequester carbon from coal, but they rarely attempt to discuss the plausibility of replacing all CO2-emitting fuel sources with renewable energy.

    What’s really lacking is a reasonable global plan to replace current fossil-fueled electricity generation and transportation with renewables.

    Comment by Ike Solem — 26 Jun 2007 @ 4:57 PM

  21. re: #15
    Given the Wall Street Journal’s editorial views, I was amused to find, today, June 26:

    1) “Climate Changes are Making Poison Ivy More Potent”, by Tara Parker-Pope.

    U of Md research, published in magazine “Weed Science” shows poison ivy (@ 400ppm CO2) compared to 1950′s 300ppm:
    - grows at almost twice the rate.
    - is hardier plant that recovers faster from grazing animals’ ravages.
    Duke U research shows that more CO2 creates more potent irritants as well.

    Kudzu is another plant that responds well to increased CO2.

    2) “Drought Wreaks Devastation in West, Southeast”, Jim Carlton & Lauren Etter. Drought, bugs, fires, not enough hay for cows (in Florida).
    ====
    Putting these two together, there’s a simple rule, which any modern farmer knows perfectly well (actually farm kids typically learn this stuff by the time they’re 10 or 12):

    Up to a plant’s genetic limits, you can increase its growth by giving it more of what it needs {sun, water, soil nutrients, CO2, right temperature range/climate pattern}, but it is always limited by whichever is *least* sufficient. You can plant cucumbers in the middle of the Sahara, and no matter how much CO2 you give them, they’re dead.

    Some plants are amazingly specific in their optimum conditions, which is one of the reasons many California towns specialize in the one fruit or vegetable that fits the best right now. This is why people like Borlaug spend their lives tinkering with plants to get variants tuned for specific local conditions.

    If warming moves a crop’s comfortable temperature zone nearer the poles, that doesn’t mean:
    - that it necessarily gets the same amount of water
    - that it has the same soil
    - that it gets as much sunlight (well, actually it gets less, for sure)

    Of course, such motion normally takes quite a while, I don’t expect the Napa vineyards in Alaska any time soon.

    It is useful to increase yield in greenhouse crops via extra CO2, in places with adequate sun and water, but that is a tiny fraction of the world’s agriculture, and doesn’t really give any practical help for staples like wheat, corn, rice, etc.

    Comment by John Mashey — 26 Jun 2007 @ 5:03 PM

  22. Spence and Raymond

    This came up with respect to another post but seems relevant here. Based on what you have written, is it correct that we should expect greater temperature changes at higher altitudes (in the mountains, not upper atmosphere)? In addition, is there data somewhere that actually shows that the increases in temperature are greater than the average for the planet as a whole.

    You said:

    “Moreover, researchers had become acutely aware of how very dry the air gets at upper altitudes â�� indeed the stratosphere has scarcely any water vapor at all. By contrast, CO2 is well mixed all through the atmosphere, so as you look higher it becomes relatively more significant.”

    On this site, I was told before that the relatively small amount of water vapor at high altitudes should result in a greater impact from co2 increases. This seems to track with the above.

    I am not talking here about the stratosphere, but it seems we do not need to go that high to observe the relative differences in changes of high vs low altitudes.

    Living at 8500 feet in the Rockies, my observation would be that the average temperature is several degrees warmer than when I was a child in the 50s. Is there any corroboration for this.

    Comment by Tom Street — 26 Jun 2007 @ 6:45 PM

  23. A bit off-track here, but something that has nagged at me for a while… When we get statements like “…an increase in average global temperature on the order of less than 1 degree centigrade…”, why are the numbers not also given in degrees F as well? Most Americans (and probably many people in other countries with a British heritage) simply don’t think in centigrade. (Much less the now PC “Celsius”.) I’ve used that scale in science since high school, and I still have to stop and mentally translate to really feel what it means.

    This might be a big part of the reason many Americans see climate change as less important than the rest of the world, because the potential temperature increases are psychologically discounted by almost half. We think that say a 3 degree increase isn’t all that much, when it’s actually, in our familiar terms, a much larger increase of almost 6 degrees F.

    Comment by James — 26 Jun 2007 @ 7:54 PM

  24. Spencer Weart> …That’s only about a percent of the solar energy absorbed by the Earth, but it’s a highly important percent to us! After all, a mere one percent change in the 280 Kelvin surface temperature of the Earth is 2.8 Kelvin…

    That statement seems either incorrect or misleading to me. With the T^4 energy radiation dependence on temperature, doesn’t the one percent forcing cause only ~1/4 percent change (0.7K) in temperature?

    Of course that is without positive feedback effects.

    [Response: Actually, I'm to blame for that particular bit of verbiage. It wasn't meant to be a quantitative estimate of the amount of warming you'd expect from a 1% change, but just to make the point that the order of magnitude of a percent of the Earth's temperature in Kelvin is a significantly large number. It's a way of saying that a 1% change in the radiation budget is not small enough to discard out of hand, and so it is necessary to do the work to find the (order unity) numerical factors needed to translate that 1% change into the corresponding percentage change in the Earth's temperature. It's Kelvins that are important rather than Celsius in this regard, because both the radiation and the thermodynamics work in Kelvins.

    By the way, you can get part of the way to the actual climate sensitivity using the T^4 law if you put in the correct (cold) radiating temperature of the planet, but water vapor feedback makes the curve of emission vs. temperature more linear than T^4, and therefore enhances the sensitivity. --raypierre]

    Comment by Steve Reynolds — 26 Jun 2007 @ 8:14 PM

  25. The text above state that doubling carbon dioxide “adds 4 Watts per square meter to the planets radiation balance for doubled CO2. That’s only about a percent of the solar energy absorbed by the Earth, but it’s a highly important percent to us! After all, a mere one percent change in the 280 Kelvin surface temperature of the Earth is 2.8 Kelvin.

    If I understand the Stefan-Boltzmann law correctly, a body radiates at the fourth power of its temperature. Therefore the first four W/m2 will cause more warming than the last four W/m2. This is why a forcing of 4 W/m2 (I thought it was 3.7 for doubled CO2) give a direct warming (before feedbacks) of 1.2 K rather than 2.8 K.

    Comment by Blair Dowden — 26 Jun 2007 @ 8:31 PM

  26. Uhh, isn’t “Herr” simply a German way to say “Mister”?

    You keep saying “Herr Koch” as if “Herr” is his first name. (Or is it his first name?) I think we usually don’t say “Mr. X” when talking of someone’s research.

    Or perhaps the custom is different for Germans…?

    [Response: He is referred to as Herr J. Koch in Angstrom's paper, so we've followed Angstrom's lead in referring to him. --raypierre]

    Comment by Jick — 26 Jun 2007 @ 9:40 PM

  27. Re: #22 I’ve tried to relocate that info here before but wasn’t able to recover it w/ the search engine.

    A point to make before elaborating might be –
    The temperature of Venus (~ all CO2 atmosphere)
    …..surface = 467C, (boiling sufur)
    …..but the expected value without a greenhouse effect = -42 C

    That ‘strongly suggests’ the Earth’s CO2 level isn’t at a saturation value.

    Comment by J. Althauser — 26 Jun 2007 @ 10:10 PM

  28. put another way, there is a lot of buried C02 and carbon and methane and so on you could eventually release. long before we got to “saturation” we’d be extinct.

    Comment by Marion Delgado — 27 Jun 2007 @ 1:11 AM

  29. this is good for the saturation argument.

    As a piecemeal it’s perfect. It leaves out the strong point that temperature and water vapor and C02 are interrelated and there is positive feedback? It kind of includes it – you visualize the C02 piling up higher and higher as it lingers (unlike water vapor at a given temperature).

    Just saying, if people still aren’t convinced, then they should be told that even if the column model doesn’t give them a convincing “feeling” contribution (in the amount of time it’s acting) they need to remember that it’s the lingering C02 raising the radiating levels increasing the temperature increasing the water vapor increasing the temperature increasing the emission of C02 which lingers …

    Comment by Marion Delgado — 27 Jun 2007 @ 1:19 AM

  30. This article was enlightening. I hope we will see more guest articles from Dr. Spencer.

    Comment by Harald Korneliussen — 27 Jun 2007 @ 1:37 AM

  31. A quick question: I occasionally run into the argument that the 0.7 degrees C warming observed as CO2 levels have increased from 273 ppm to 383 ppm suggests a lower climate sensitivity, because we are already 40% of the way to a doubling of pre-industrial CO2 levels and we would expect greater radiative forcing changes to occur from the initial addition of CO2 given the relationship between CO2 and wavelength absorption described in this post.

    The obvious answer is that we are not currently at the “equilibrium” temperature that would accompany a 383 ppm CO2 concentration due to the thermal inertia of the ocean, but am I missing anything else? Also, is there a good chart available of the best guess equilibrium temperatures associated with different levels of CO2?

    Comment by Zeke Hausfather — 27 Jun 2007 @ 4:05 AM

  32. Re 15, 16, 21 The main factor that limits food production is not CO2 or water or crop physiology its money. Farmers with money can apply technology to overcome other constraints to agriculture. Those without can not. How productive would California agriculture be if the only technology available was hand tools and human labour?

    Comment by Paul — 27 Jun 2007 @ 4:14 AM

  33. [[Are you assuming that CO2 concentrations are consistent (evenly distributed) throughout the vertical entirety of the atmosphere? It seems to me (based purely on intuition) that CO2 concentrations would be decreasingly significant with altitude, such that the top-most layers of the atmosphere would experience very little change in CO2 concentration. How much of the CO2 in the atmosphere actually exists up there? What percentage of all CO2 exists in the stratosphere? ]]

    Intuition is misleading in this case. You might expect gases to be stratified by molecular weight, in which case all the carbon dioxide would be low down, since CO2 has a molecular weight of 44 and the mean MW of air is only 29. But it doesn’t work out that way. Turbulence due to convection (a form of heat transfer due to warm parcels of air rising and cool ones falling) keeps the troposphere well mixed. (The troposphere is the lowest layer of the atmosphere, from the ground to about 11 kilometers high on average.)

    Comment by Barton Paul Levenson — 27 Jun 2007 @ 5:59 AM

  34. [[In the mean time, as CO2 levels continue to rise, poison ivy will also thrive (http://www.sciencenews.org/articles/20060603/fob1.asp). More cucumbers and poison ivy - it doesn't get much better than that!]]

    The last time I tried to eat poison ivy my tongue became inflamed and I had to soak it in calamine lotion for 15 days. I had to cancel all my speaking engagements.

    Comment by Barton Paul Levenson — 27 Jun 2007 @ 6:01 AM

  35. For what it is worth, Lubos Motl has a few things to say about this post.
    http://motls.blogspot.com

    [Response: Indeed. And as usual with Motl's stuff, it's not worth much. In a rather confused and roundabout way, he seems to have rediscovered that the radiative forcing due to CO2 is logarithmic in CO2 concentration, and to think that's news. It's also a howler that he took Spencer to task for trying to explain it all without graphs or equations; the graphs of course are in Part II, the equations are in the references, and what RC is all about is trying to make climate science comprehensible to people who can't take off a few years do do a graduate degree in the subject. Naturally, one achieves a deeper understanding on the basis of mathematics, but if something can be said to be understood at all, it should be possible to convey some of the essential truth in plain language. I think Spencer did a fine job of that. Motl is a good example though,of how being capable of doing the mathematics is no guarantee of actually being able to derive understanding from it. --raypierre]

    Comment by Sam — 27 Jun 2007 @ 8:24 AM

  36. Re 34 poison ivy

    Deer seem to love it!
    Global warming –> more poison ivy –> more deer
    Great! Just what we need.

    Comment by Chuck Booth — 27 Jun 2007 @ 9:04 AM

  37. Zeke Hausfather (#31) wrote:

    A quick question: I occasionally run into the argument that the 0.7 degrees C warming observed as CO2 levels have increased from 273 ppm to 383 ppm suggests a lower climate sensitivity, because we are already 40% of the way to a doubling of pre-industrial CO2 levels and we would expect greater radiative forcing changes to occur from the initial addition of CO2 given the relationship between CO2 and wavelength absorption described in this post.

    The most important point we are still not in balance in terms of radiation leaving the planet being equal to the amount of radiation entering the system – it takes a while for the temperature to rise to the point that the radiation leaving the system becomes equal to that which is entering the system – but I would assume that in part this is the inertia associated with the ocean. Then various feedbacks aren’t instantaneous. For example, the effects of carbon dioxide being applified by water vapor.

    Comment by Timothy Chase — 27 Jun 2007 @ 9:33 AM

  38. re: #20

    “However, few if any of the science journalists who discuss climate change and global warming ever make the connection to renewable energy. Articles on global warming focus on the need to reduce emissions of to sequester carbon from coal, but they rarely attempt to discuss the plausibility of replacing all CO2-emitting fuel sources with renewable energy.”

    This may not respond specifically to your remark, but does seem to addresses the overall problem being faced. It’s from Sigma XI website, the folks who publish “American Scientist” magazine, where I first saw the executive summary of the follwing report:

    “Confronting Climate Change: Avoiding the Unmanageable and Managing the Unavoidable”

    http://www.sigmaxi.org/about/news/UNSEGReport.shtml

    I haven’t had a chance to read it in depth yet, only skim it, but from the perspective of sustainability, it seems pretty solid.

    Also, given as you brought up alternatives, I was wondering if you could address something that came up in conversation recently regarding water vapor as a GHG. Perhaps a stupid question, but what the heck.

    It was suggested mentioned that hydrogen powered vehicles would be less polluting than the standard internal-combustion engine largely because they expel water vapor. (I’m sure I’m being imprecise here).

    So, he wondered, is anyone aware of any calculations regarding what might happen if over a billion hydrogen powered cars were all operating and expelling water vapor? Would this cause an increase in GHGs that would rival the problems we see with CO2? What about local humidity rates, that sort of thing?

    Thanks in advance.

    Lastly, a little more off-topic but still in the arena, the current American Scientist has an interesting piece on coal:

    http://www.americanscientist.org/template/AssetDetail/assetid/55574;jsessionid=baacFyMVD1uQq8

    Regards,

    [Response: It's off-topic, but at the risk of inconsistency with my plea further down, I have to say I'm glad you posted a pointer to this article. It's really thought-provoking. I have been looking into coal reserves myself a bit, and I think that eventually I ought to do a post on the question of how much coal there really is, and how we know; that would provide a good forum for discussing these issues. --raypierre]

    Comment by J.S. McIntyre — 27 Jun 2007 @ 9:58 AM

  39. Is rising CO2 level really good for farmers? Maybe not…
    check out this:
    http://globalecology.stanford.edu/DGE/Dukes/JRGCE/home.html

    Comment by Andrew Varga — 27 Jun 2007 @ 10:10 AM

  40. PS Response to Zeke Hausfather (#31) from #37

    One really good feedback to include which takes time to fully come into effect is the melting of ice, including polar sea ice. It is nice and visual. Melting will take years – as each summer will eat away at the ice a little more – and the increase in absorbed light will result in more melting until the long-term equilibrium is reached. This is included in the sensitivity to carbon dioxide doubling.

    However, by definition, we are not including feedbacks from the carbon cycle itself. For example, the release of methane from thaw lakes in Siberia or the reduced ability of the ocean and plants to absorb carbon dioxide. These will result in a higher long-term level of carbon dioxide than what we ourselves emit – and this is particularly important to keep in mind when comparing our artificial climate change which was is do to our driving the carbon/temperature feedback to the natural climate change of the past where it was an increase in temperature which drove the carbon/temperature feedback loop.

    This difference will increasingly become a factor the longer it takes for us to reduce our emissions.

    Comment by Timothy Chase — 27 Jun 2007 @ 10:51 AM

  41. re 38:

    So, he wondered, is anyone aware of any calculations regarding what might happen if over a billion hydrogen powered cars were all operating and expelling water vapor? Would this cause an increase in GHGs that would rival the problems we see with CO2? What about local humidity rates, that sort of thing?

    The atmosphere is very good at regulating water vapor. Once you saturate water vapor in the air, adding more just gives you fog and rain. So the GW calculations would mostly fall in an area that is still under study, the effect of clouds. I think they still don’t have solid answers on clouds, even to the point of being able to say that they would be a net positive or negative feedback. Lots of particulars come in to play with clouds (cloud hight, time of day, etc)

    As to the effect of a billion hydrogen powered cars, if each emits the vapor equivalent of 10 liquid gallons per day(which seems high, but is useful for ease of calculation) then you have an extra 10 billion gallons of rain per day. By comparison, average US stream flow is 1,200 billion gallons per day (a USGS number). So there would be more rain, but not an overwhelming amount, globally. What that might do the local ecologies in places like Phoenix is another question, however.

    Comment by Tim McDermott — 27 Jun 2007 @ 11:01 AM

  42. Andrew Varga (#39) wrote:

    Is rising CO2 level really good for farmers? Maybe not…
    check out this:

    http://globalecology.stanford.edu/DGE/Dukes/JRGCE/home.html

    By itself, increasing the level of carbon dioxide up to a point will be good for many plants. However, raising the temperature will result in heat stress, and raising the temperature will tend to result in water evaporating more quickly from the soil. This will become increasingly important in the US south west, then in the US south east. Additionally, it will change the precipitation patterns – with more rain falling close to where the evaporation takes place, namely the ocean.

    Then as glaciers disappear, it will result in less glacier runoff. In this case a good example would be the six major rivers of China which will dry up as the glaciers in the Himalayas disappear. These glaciers will be gone by 2100, resulting in a drastic reduction of agricultural output in the region – and will affect food prices worldwide.

    [Response: We're getting rather off-topic here with this discussion of agriculture. Could we get back to saturation, water vapor, and perhaps feedbacks instead? --raypierre]

    Comment by Timothy Chase — 27 Jun 2007 @ 11:07 AM

  43. raypierre (inline #42) wrote:

    Response: We’re getting rather off-topic here with this discussion of agriculture. Could we get back to saturation, water vapor, and perhaps feedbacks instead?

    Agreed. My apologies.

    [Response: No problem. People should feel free to bring up what's of interest to them, and if things stray too far, one of us will just gently nudge the discussion back in the right direction. --raypierre]

    Comment by Timothy Chase — 27 Jun 2007 @ 11:39 AM

  44. #35 The clearest statement in Motl’s essay that differs from Ray Pierrehumbert’s is his conclusion about C02 saturation: he argues that saturation would have already occurred by the time C02 doubled and the warming effect would be only 0.3C. Whereas R.Ph is saying that saturation will never be reached. Of course, waiting to find out who’s right isn’t an option, though I suspect that’s what Motl & Co want.

    One of his in-house regulars also dismisses the question of stratospheric C02 having any significance. From what I’ve read though, this has been studied from the 60′s onwards by aircraft and radiosonde studies and they’ve found increasing concentrations in the stratosphere. So I wonder what the real story is on this?
    A couple of obvious problems strike me with Motl’s arguments right away:-
    1) He seems to totally ignore the question of whether observed global warming has been less than predicted due to the oceanic absorption of C02 – which has been observed to be breaking down in the southern ocean.
    2) His observational evidence is virtually nil. He constantly excludes evidence of warming, while any tiny localised event that demonstrates cooling is seized upon as significant.
    At least he’s now admitting the “greenhouse effect” actually exists. If so, why doesn’t he discuss the evidence seriously?

    [Response: You don't need to wait to find out who's right. The lab spectroscopy measurements already show that the standard view (represented by my piece with Spencer and my technical addendum) is correct. The spectroscopy is simply not in question -- this is absolutely standard stuff. That shows that the atmosphere isn't even saturated in the sense thought of by Angstrom. As for the "thinning and cooling" argument, that is explained with crystal clarity using the analytic solution for a grey or semi-grey atmosphere, available many places (my book included). It only involves the solution to the simplest kind of first order constant-coefficient ordinary differential equation, which a string theorist like Motl should be quite capable of handling. Moreover,the "thinning and cooling" argument -- that the brightness temperature depends only on the layer from which radiation escapes to the observer -- is absolutely standard stuff in physics. The core of the Sun is some tens of millions of degrees. You don't see that when you look at the sky, do you? The core of the Earth is several thousand degrees. You don't see that when you look at the ground, do you? It would be incandescent if you did. You don't see it because you see radiation at the temperature of the level from which the radiation can escape. It's that simple. Atmospheric IR is no different. If you are used to the "photosphere" of the sun, just think of what we're talking about as the "IRsphere" of the Earth. Same stuff. You can draw your own conclusions about why he doesn't seem to be able to understand this stuff. --raypierre]

    Comment by Alex Nichols — 27 Jun 2007 @ 11:48 AM

  45. Re Schmidt response to #15: Mr Schmidt should read the paper before shooting from the hip. Perhaps you can enlighten your readership as to why increased and diminished plant growth based upon CO2 concentration is unlikely. Are there other peer reviewed papers that show contradictory results? Real Climate is supposed to be a professional scientific weblog. Why not function like one?

    [Response: A modicum of politeness please. My comment was related to your last line about the prospects for CO2 levels lower than those of today. I do not need to know anything about plant growth to know that neither you nor I will see CO2 levels lower than today's in our lifetime. Thus discussions about the fate of plants under those circumstances are, to say the least, moot. - gavin]

    Comment by W F Lenihan — 27 Jun 2007 @ 11:59 AM

  46. W F Lenihan (#45) Re carbon dioxide and plant growth…

    See #42 but if you wish to consider continuing this topic, per #43 consider a different thread as a matter of courtesy to the authors of the current essays.

    Comment by Timothy Chase — 27 Jun 2007 @ 12:35 PM

  47. Ray, your explanation to the first question raised in comment 6 (as to why the stratosphere cools while the troposphere warms when atmospheric CO2 concentration increases) is a bit off-target and incomplete.

    The main cause for the stratospheric cooling & tropospheric warming effect is really due to the “split spectrumâ�� nature of the terrestrial atmosphere, i.e., there is a “window” region in the 10 micron vicinity with little opacity, while there is very strong opacity (due to CO2) in the 15 micron region.

    In a simple grey-opacity greenhouse model, as atmospheric opacity is increased, the greenhouse effect causes to surface temperature to increase. If the atmospheric opacity is very small, the ratio of the local temperature at the top of the atmosphere (TOA) to the local temperature at the bottom of the atmosphere (BOA) will be near unity. As the atmospheric opacity increases, the atmospheric temperature gradient will increase, and TOA/BOA temperature ratio will decrease, going to zero as atmospheric opacity (and surface temperature) approach infinity.

    With the crude grey-opacity model, as the atmosphere becomes more and more opaque, the top of the atmosphere has to maintain a local temperature that is equal to the effective radiating temperature in order to maintain energy balance with the absorbed solar radiation. Thus there can be no real stratospheric cooling with the grey-opacity model while the troposphere continues to warm as CO2 is increased.

    But with a more realistic radiative model (one that properly accounts for the atmospheric window region), the ground surface can radiate directly to space within the 10 micron window region. In this case, when CO2 is increased, the greenhouse effect will warm the surface temperature (and increase the radiative flux that is emitted directly from the ground to space), and the stratosphere will cool because it is being shielded more strongly from upwelling radiation from below by the increased opacity in the 15 micron region. Thus, energy balance with absorbed solar radiation will be maintained by an increase in 10 micron spectral flux (from the ground) and a corresponding decrease in 15 micron spectral flux (from the stratosphere).

    [Response: There are no end to wrinkles on this problem of stratospheric cooling, and of course there are a whole lot of things going on in the stratosphere. The mechanism I outlined does work in simple models, but I do appreciate the additional insights. Clearly, the stratospheric emission has to be in a limited wavenumber band if you're going to get the cooling while still respecting the planetary radiation balance. In my book I describe the split-spectrum issue as well as the absorption/emission issue, but I couldn't figure an easy way to explain that in a comment. Hopefully your explanation will be of some use to our readers. I'm not sure I entirely agree with you regarding your comment on the grey-opacity case, if you include the effects of upper level solar absorption. That's apt to take us into technical issues that may not be of interest to the readers, so we can pursue that elsewhere. --raypierre]

    Comment by Andy Lacis — 27 Jun 2007 @ 1:36 PM

  48. #44 “You can draw your own conclusions about why he doesn’t seem to be able to understand this stuff”

    Don’t worry, I drew those conclusions some time ago.
    Some telling points in your last comment.

    Comment by Alex Nichols — 27 Jun 2007 @ 1:38 PM

  49. Just to clarify, there don’t seem to be separate estimates for the doubling CO2 climate sensitivity for the case without water vapor feedback. The uncertainties in the climate sensitivity estimates (1.7-4.5 C) are related primarily to the strength of the water vapor feedback and the role that clouds play. If the global sensitivity of 3C, then it seems certain that all of Greenland will melt, though it make take a thousand years to do so, or a hundred. That will raise sea levels 7 meters, right? The fastest recorded rate of sea level rise in the past is 3-4 mm/year, or 3-4 meters/century. Global warming is accompanied by polar amplification processes, as well.

    Here’s an interesting question: suppose we halted all CO2 emissions today. What would be the equilibrium sea level rise for that case? How long would it take to occur?

    Comment by Ike Solem — 27 Jun 2007 @ 1:56 PM

  50. Ike,

    You made a small math error. 3 – 4 mm/yr equates to 0.3 – 0.4 meters/century. I’m concerned that we may see 30 – 40 mm/year in our lifetime, but we haven’t seen it yet.

    Comment by Phillip Shaw — 27 Jun 2007 @ 2:45 PM

  51. In response to:

    Turbulence due to convection (a form of heat transfer due to warm parcels of air rising and cool ones falling) keeps the troposphere well mixed. –Barton Paul Levinson

    …and…

    The concentration is higher in the stratosphere. And we have known this since 1969. –Timothy Chase

    Well, the Georgii quote you(Timothy) provided said quite the opposite, and that there was a decrease in CO2 ppm moving upward and that it was not consistently mixed: “The marked decrease of the CO2 concentration in the lower stratosphere compared with the upper troposphere suggests that, contrary to previous practice, it is wrong to assume a constant mixing-ratio of CO2 in the troposphere and stratosphere.”

    But I was more curious as to whether there was a smooth, linear decrease with altitude rather than with a sudden drop.

    [Response: There's a detectable drop in CO2 as you go into the stratosphere from the troposphere, because it takes some time to mix it upward. There's also a detectable interhemispheric difference in mixing ratio in the troposphere. These are all very interesting for what they tell us about mixing and about sources and sinks, but the variations in mixing ratio are too small to be of much importance for radiative transfer. --raypierre]

    Comment by DaveS — 27 Jun 2007 @ 3:06 PM

  52. re: #32
    Money certainly helps, but that’s ill-informed about farming, because cost-effectiveness matters, a lot.

    But, this leads me to a question/suggestion for RC: given the highly multi-disciplinary nature of climate science, maybe it would be good to recruit an expert guest poster who could talk about the intersection of climate science with agricultural/bioscience research/ag engineering, etc …

    For instance, my alma mater Penn State has a large College of Agricultural Sciences: http://www.cas.psu.edu/
    Maybe Prof. Mann knows somebody relevant there.

    5 minutes’ rummaging found “Predicting Pests”:
    http://aginfo.psu.edu/PSA/07WinSpr/Pests.html

    “entomologist Dennis Calvin and his research team look at how climate and weather influence the timing of insect emergence in field crops.”

    “Asian soybean rust… needs green soybeans or kudzu leaves to grow, and therefore it can survive only in the deep South, where winters are warm…We speculate that in years when the deep South has a warm and wet spring, this pathogen will be a serious widespread problem.”

    Here in CA, UC Davis is quite strong, and there are of course many schools with fine programs, as many American land-grant universities started as ag schools, and many bioscience and environmental departments have some heritage there. Really, agricultural research is way beyond “throw infinite money at the problem”, which doesn’t work.

    Anyway, we should keep biology out of the physics discussions, but maybe a little more well-informed biology discussions would be relevant to RC?

    Comment by John Mashey — 27 Jun 2007 @ 3:31 PM

  53. Regarding this (5th. paragraph) action summary =>

    “What happens to infrared radiation emitted by the Earth’s surface? As it moves up layer by layer through the atmosphere, some is stopped in each layer. To be specific: a molecule of carbon dioxide, water vapor or some other greenhouse gas absorbs a bit of energy from the radiation . . . (so that) . . . the layer of air where it sits gets warmer. The layer of air radiates some of the energy it has absorbed back toward the ground, and some upwards to higher layers. . . . Eventually the energy reaches a layer so thin that radiation can escape into space.”

    —- I’m a little surprised that there is no mention of the governing equations for this absorption/re-radiation: the (1905/06) Schuster-Schwartzchild Equations of Transfer.

    I have an evalaution set out in this article => Essenhigh, R.H.: Prediction of the Standard Atmosphere Profiles of Temperature, Pressure, and Density with Height for the Lower Atmosphere by Solution of the (S-S) Integral Equations of Transfer and Evaluation of the Potential for Profile Perturbations by Combustion Emissions. Energy and Fuels: 20, 1057-1066 (2006)

    Comment by Robert H. Essenhigh — 27 Jun 2007 @ 3:47 PM

  54. DaveS (#51) wrote:

    The concentration is higher in the stratosphere. And we have known this since 1969. –Timothy Chase

    Well, the Georgii quote you(Timothy) provided said quite the opposite…

    Sorry – I was in a hurry – at work at the time.

    Something slightly more recent…

    Here we report mid-latitude vertical profiles of CO2, up to 35 km, measured in 1979, 1982 and 1984 by analysing cryogenically collected balloon samples supplemented by air samples taken aboard aircraft. CO2 mixing ratios are not constant with altitude but rather decrease by 7 p.p.m.v. (parts per 10^6 by volume) from the tropopause to the mid-stratosphere.

    Increased concentration and vertical distribution of carbon dioxide in the stratosphere (abstract only)
    W. Bischof, R. Borchers, P. Fabian & B. C. Kruger
    Nature 316, 708 – 710 (22 August 1985)
    http://www.nature.com/nature/journal/v316/n6030/abs/316708a0.html

    In this context, “roughly constant” or well-mixed would seem to be a good approximation – as ppm would have been above 300 ppm, I presume, and we are speaking of its effects being logarithmic.

    Then the make the same point that raypierre made regarding the lag:

    The growth rate of the atmospheric CO2 abundance caused by anthropogenic emission, which varies between 1.0 and 1.5 p.p.m.v. yrâ??1 at ground level1, is also observed at all stratospheric heights up to 35 km. The shape of the profiles suggests that excess CO2 above 20 km enters the stratosphere through tropical upwelling rather than mid-latitude diffusion. The time lag of this height region with respect to the tropospheric CO2 level is 5 yr.

    Five year lag – through tropical upwelling.

    Anyway, my apologies about quoting abstracts on this topic, but this doesn’t seem to be a “hot topic” anymore, and abstracts are all I have. (I am not in the field, but work as a coder for software that tracks cell phone network performance.)

    Comment by Timothy Chase — 27 Jun 2007 @ 4:10 PM

  55. Couple of questions. First, can you show (on the graph in Part 2) the lines for 8x and 16x increases in CO2? That would go very far in clarifying the nature of the relationship.

    Second, is it true that heat is radiated from atmospheric GHG molecules at different wavelengths than it was aborbed? If so, how does this affect the how the radiated energy is absorbed by other molecules? Is the difference constant or does it vary by some other factor?

    Comment by Alfy — 27 Jun 2007 @ 4:16 PM

  56. #33 Barton Paul Levnson:

    If memory serves me, Henry Bauer said one of Immanuel Velikovsky’s early forays into science involved him assuming that gases were stratified by molecular weight, and a fairly stubborn refusal to accept correction on the issue :)

    Comment by Marion Delgado — 27 Jun 2007 @ 9:49 PM

  57. This is great, as a recent Science article raised the issue, or complaint, that IPCC global warming models did not address the stratosphere but only the troposphere. What would be the difficulties in amending those models to include activity in the stratosphere?

    [Response: Almost all the models have a stratosphere of some sort, though there are not generally enough points in the stratosphere to satisfy professional stratospheric dynamicists. Probably the article was complaining not so much about the modelling itself as the degree of attention paid to the influence of what is going on in the stratosphere. As long as you're not talking about adding in chemistry, most models can improve their representation of the stratosphere simply by adding in more points in the vertical, which isn't even that expensive computationally. The relative importance of stratospheric processes in tropospheric climate change is a matter of some debate. --raypierre]

    Comment by Furia Fubar — 27 Jun 2007 @ 10:36 PM

  58. There is different band saturation argument going around. This argument goes, if I understand it correctly, that the rate of energy transfer for CO2 is saturated. I think that means that the ratio of transmitted radiation to incident radiation isn’t constant as a function of incident radiation intensity at the levels present in the atmosphere because CO2 can’t transmit energy fast enough either by collisional deactivation or emission. My gut feeling is that this is total BS because I suspect the energy density in a basic IR spectrometer is orders of magnitude higher than that from the surface of the earth, and I don’t think Beer’s Law is violated then. Are you familiar with this argument and is there a quick and dirty answer?

    [Response: I hadn't heard this argument before, but your gut feeling is right. Laboratory spectroscopy that is used to feed the HITRAN archive is done in conditions similar to those prevailing in the atmosphere, and if there were some problem of the sort you mentioned, it would be seen already in the spectrometers. --raypierre]

    Comment by DeWitt Payne — 27 Jun 2007 @ 11:50 PM

  59. Very interesting. Thanks for exposing yet another gimmick.

    Thing is, it doesn’t matter that it’s wrong, so long as it’s convincing enough that you can manufacture a public sense of uncertainty about the basics of the greenhouse effect.

    A two-layer (surface and core separated by opaque gas) model for the Sun doesn’t work too well either, but nobody would be crazy enough to suggest that it should. On the other hand, it is well-known and established for the better part of a century that changing opacities in one place can have profound effects on conditions elsewhere (such as the core). There’s nothing controversial about it, but then again, there’s no big corporate interest trying to persuade us that we got our rad transfer all wrong in that case.

    Comment by Peter Williams — 28 Jun 2007 @ 1:11 AM

  60. Hey, I checked out Lubos Motl’s page – He’s clearly a very smart person, but he should stick to stuff he knows. Typical theorist.

    Notice that Motl doesn’t actually set up a model with multiple layers and numerically solve the radiative transfer problem; he’s really just doing a back-of-the-envelope calculation. String theorists as a rule tend to think that if you can’t solve something analytically it’s not worth solving.

    I try to avoid ad hominem, but geez, it really is awfully smarmy to bash Weart with a statement like “It is not that difficult and a good physicist knows how to solve the differential equations that arise in this context.” (re the effect of many layers of CO2, versus a simple one-layer model), AND THEN not to bother either to write down the relevant differential equations, much less solve them! Talk about being a hypocrite! I know some theorists think that if it’s not Yang-Mills or twistor theory then it’s mathematically trivial, but hey Motl, perhaps you could pick up a copy of Chandrasekhar or Mihalas & Mihalas and go teach yourself some plane-layer radiative transfer methods before you go off making such a fool of yourself again. Yes, you do in fact need to know more than just the total column density of CO2, unless you just like to solve Fermi problems.

    Comment by Peter Williams — 28 Jun 2007 @ 2:00 AM

  61. This is a little bit off-topic, but perhaps not. At glacial maximum, with the oceans three hundred feet lower, is there any effect on the atmosphere? At the Dead Sea, I’ve heard that the atmosphere is much denser, but that is an isolated pocket. Is there any correlation between global climate and sea level?

    Comment by Mark R — 28 Jun 2007 @ 3:23 AM

  62. [[A quick question: I occasionally run into the argument that the 0.7 degrees C warming observed as CO2 levels have increased from 273 ppm to 383 ppm suggests a lower climate sensitivity, because we are already 40% of the way to a doubling of pre-industrial CO2 levels and we would expect greater radiative forcing changes to occur from the initial addition of CO2 given the relationship between CO2 and wavelength absorption described in this post.
    The obvious answer is that we are not currently at the "equilibrium" temperature that would accompany a 383 ppm CO2 concentration due to the thermal inertia of the ocean, but am I missing anything else? Also, is there a good chart available of the best guess equilibrium temperatures associated with different levels of CO2?
    ]]

    The argument assumes that there are only two factors involved, CO2 and temperature. In reality several factors are involved. Negative forcings like sulfate aerosols and volcanic eruptions have caused some cooling. The point you raise is also valid; some of the warming is still “in the pipeline” and will show up (is already showing up) in the future.

    Comment by Barton Paul Levenson — 28 Jun 2007 @ 6:28 AM

  63. [[So, he wondered, is anyone aware of any calculations regarding what might happen if over a billion hydrogen powered cars were all operating and expelling water vapor? Would this cause an increase in GHGs that would rival the problems we see with CO2? What about local humidity rates, that sort of thing?]]

    It wouldn’t matter, because water vapor rains out quickly, on average in 9 days, whereas CO2 stays up an average of 200 years.

    Comment by Barton Paul Levenson — 28 Jun 2007 @ 6:30 AM

  64. #63

    Been wondering whether to post this as it sounds like I’m a snide sceptic but a billion H2 powered cars continuously emanating water vapour? Not taking a break for 9 days? Ah well, answering my own question, if it did become a problem I suppose the WV could be condensed at source.

    Keep posting Barton as I do look out for yours.

    Comment by Mike Donald — 28 Jun 2007 @ 7:29 AM

  65. Re #63 A billion cars producing H20

    I can see that there would be no problem with H2O, but what about leakage of hydrogen on a massive scale?

    Comment by Dick Veldkamp — 28 Jun 2007 @ 8:49 AM

  66. RE 62: “The point you raise is also valid; some of the warming is still “in the pipeline” and will show up (is already showing up) in the future.”

    The point is frequently made that the oceans delay atmospheric temperature rise, so that the rest of the expected air temperature increases are in the pipeline and will be coming shortly. This is logical as the atmosphere is well mixed and in contact with the ocean. I live near the cold ocean in the Gulf of Maine and can attest to the cooling impact it has on air temperature. We also are well aware of the 800 to 1,000 year “delay” in the co2 response to air temperature as depicted in the long-term ice core data. The thought there being that co2 is released from the ocean as the ocean warms, but it takes 800 to 1,000 years to fully warm. My question is: Is the warming that is in the pipeline going to take 800 to 1,000 years to play out? If so, it does not appear to be a significant factor in the warming to occur this century. I have never seen an estimate of the delay relative to this century.

    Comment by Sam — 28 Jun 2007 @ 9:37 AM

  67. Sam (#66) wrote:

    We also are well aware of the 800 to 1,000 year “delay” in the co2 response to air temperature as depicted in the long-term ice core data. The thought there being that co2 is released from the ocean as the ocean warms, but it takes 800 to 1,000 years to fully warm. My question is: Is the warming that is in the pipeline going to take 800 to 1,000 years to play out? If so, it does not appear to be a significant factor in the warming to occur this century. I have never seen an estimate of the delay relative to this century.

    The following should give you a few figures. For example, according to our calculations, 50% of the temperature rise should occur within the first twenty-five years.

    The model has sensitivity 2.7oC for doubled CO2 when coupled to the Q-flux ocean (Efficacy, 2005), but 2.9oC when coupled to the Russell et al. (1995) dynamical ocean. The slightly higher sensitivity with ocean C became apparent when the model run was extended to 1000 years, as the sea ice contribution to climate change became more important relative to other feedbacks as the high latitude ocean temperatures approached equilibrium. The 2.9oC sensitivity corresponds to 0.7oC per W/m2. In the coupled model with the Russell et al. (1995) ocean the response to a constant forcing is such that 50% of the equilibrium response is achieved in 25 years, 75% in 150 years, and the equilibrium response is approached only after several hundred years. Runs of 1000 years and longer are available on the GISS web site. The modelâ??s climate sensitivity of 2.7â??2.9oC for doubled CO2 is well within the empirical range of 3 +/-1oC for doubled CO2 that has been inferred from paleoclimate and other observational evidence (Hansen et al., 1984, 1993; Hoffert and Covey, 1992; Annan and Hargreaves, 2006).

    pg. 2289

    Dangerous human-made interference with climate: a GISS modelE study
    Hansen, et al.
    Atmos. Chem. Phys., 7, 2287â??2312, 2007
    http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_1.pdf

    Comment by Timothy Chase — 28 Jun 2007 @ 10:54 AM

  68. [[I can see that there would be no problem with H2O, but what about leakage of hydrogen on a massive scale?]]

    Might be a fire hazard in the immediate vicinity, I suppose.

    Comment by Barton Paul Levenson — 28 Jun 2007 @ 11:04 AM

  69. [[The thought there being that co2 is released from the ocean as the ocean warms, but it takes 800 to 1,000 years to fully warm. My question is: Is the warming that is in the pipeline going to take 800 to 1,000 years to play out? If so, it does not appear to be a significant factor in the warming to occur this century. I have never seen an estimate of the delay relative to this century. ]]

    I think the release in a normal deglaciation takes that long because the temperature changes that drive it take that long — the slow changes in Earth’s orbit and axial tilt that drive ice age/deglaciation cycles. In the present case, we’re warming up the Earth many times faster than that, so we could have problems with ocean-released CO2 much faster.

    Comment by Barton Paul Levenson — 28 Jun 2007 @ 11:06 AM

  70. Re #65:

    I can see that there would be no problem with H2O, but what about leakage of hydrogen on a massive scale?

    I read a report a couple of years ago claiming that H2 is an ozone-destroying molecule, so if the “hydrogen economy” emerges, it will wreck the ozone layer.

    Comment by Jim Galasyn — 28 Jun 2007 @ 11:09 AM

  71. Is lubos Motl actually a real scientist or a highly educated politically motivated scientific activist ?

    He seems to pretend to know but does he know ? Being based at a prestigous university you would conclude that he was a intelligent and objective individual but he sound somewhat politically motivated to me.

    Comment by pete best — 28 Jun 2007 @ 11:22 AM

  72. Re #67. The reference is:

    Potential Environmental Impact of a Hydrogen Economy on the Stratosphere
    Tracey K. Tromp, Run-Lie Shia, Mark Allen, John M. Eiler, Y. L. Yung
    Science 13 June 2003: 1740

    Abstract:
    “The widespread use of hydrogen fuel cells could have hitherto unknown environmental impacts due to unintended emissions of molecular hydrogen, including an increase in the abundance of water vapor in the stratosphere (plausibly by as much as ~1 part per million by volume). This would cause stratospheric cooling, enhancement of the heterogeneous chemistry that destroys ozone, an increase in noctilucent clouds, and changes in tropospheric chemistry and atmosphere-biosphere interactions.”
    This abstract is available, with some references to the article, at:
    http://www.sciencemag.org/cgi/content/abstract/300/5626/1740

    The authors apparently admit the effect described depends on how much H2 would get absorbed into the soil. Critics say they greatly overestimated likely leakage rates. I suspect the whole question is moot because of the infrastructural costs of switching to hydrogen-fueled cars – either plug-in-anywhere hybrids, or battery-driven cars with battery-swap stations are probably better bets. Less private car use even better.

    Comment by Nick Gotts — 28 Jun 2007 @ 12:01 PM

  73. # He is a real scientist and a quite talented one, but on his site, describes himself as a “reactionary physicist”.
    It seems to have all started when the former Dean at Harvard, Laurence Summers was replaced for making statements to the effect that women weren’t as good at science as men and not supporting positive action on entry to courses.

    Motl painted himself into a bit of a corner by supported Summers and has adopted increasingly ‘politically incorrect’ statements ever since. I thinks he’s nearly applied 16 coats by now.

    He’s been described as the “string enforcer” by certain elements in the physics community, who find his method of debate a bit over the top. He’s usually regarded as a bit of a troll on their web sites nowadays.

    I’m not sure of his current relationship with Harvard University, but he seems to be devoting an awful lot of time to supporting the denialist camp in the AGW debate.

    Heaven only knows why…

    Comment by Alex Nichols — 28 Jun 2007 @ 12:11 PM

  74. Barton Paul Levenson (#68) wrote:

    [[I can see that there would be no problem with H2O, but what about leakage of hydrogen on a massive scale?]]

    Might be a fire hazard in the immediate vicinity, I suppose.

    There exist materials for the safe storage of hydrogen in relatively compact space. I could look this up a little later if nobody beats me to it. Additionally, hydrogen burns at a lower temperature than gasoline – and it does tend to float and get dispersed by the wind rather than pool at the surface or remain on one’s clothes while it burns.

    Comment by Timothy Chase — 28 Jun 2007 @ 12:16 PM

  75. Re my #72: sorry, when it says “Re #67″ it should say “Re #70″.

    Comment by Nick Gotts — 28 Jun 2007 @ 12:36 PM

  76. Re #72,

    Thanks for digging up that citation, Nick!

    Comment by Jim Galasyn — 28 Jun 2007 @ 1:52 PM

  77. Timothy Chase wrote: “There exist materials for the safe storage of hydrogen in relatively compact space.”

    Here is an example from ECD Ovonics, who also manufacture thin-film amorphous silicon photovoltaics:

    We are developing a new, practical approach to storing hydrogen in a safe and economical manner. Using our proprietary, atomically engineered materials technology, ECD Ovonics has developed a family of new, efficient metal hydrides which store hydrogen in a solid metal matrix at low, practical pressures.

    Proprietary ECD Ovonics metal hydrides are alloys that are specifically formulated according to new principles to absorb hydrogen much like a sponge absorbs water. When hydrogen is absorbed, it bonds to the metal alloy, releasing heat. Conversely, when heat is absorbed, the alloys release hydrogen to a fuel cell or internal combustion engine (ICE) which can subsequently power a broad range of commercial applications. By using ECD Ovonics atomic engineering principles, materials can be tailored over a wide range of pressures and temperatures to meet the performance parameters of a particular application.

    Ovonic metal hydrides offer an essential solution to overcoming the intermittency concerns of renewable power systems. Since metal hydrides store hydrogen at low pressure, they can accept hydrogen directly from an electrolyzer. Coupled with renewable sources, such as Ovonic multi-junction photovoltaic products, a hydrogen co-generation system can store energy in the form of hydrogen for later use when the renewable source is not available, or when extra power may be needed for load-leveling purposes.

    Comment by SecularAnimist — 28 Jun 2007 @ 2:08 PM

  78. My memory and knowledge are fuzzy, but I have a couple of questions on H2-powered vehicles I need clarifying. To be effective doesn’t the H2 need to be manufactured on board as needed from hydrocarbons, and isn’t that process currently too slow, energy intensive, and cumbersome for that? If pure H2 is stored (in liquid form??) on the vehicle it seems the fire/explosive hazard would be prohibitive, but, more significantly, wouldn’t the “gas tank”, to handle the high pressure, need 2-4 tons of thick high-grade steel? Wouldn’t all of this make H2 a non-starter? Or am I way behind the times and science?

    Comment by Rod B — 28 Jun 2007 @ 2:43 PM

  79. I find it somewhat amusing that the arguments espoused by denialists today were effectively scuttled half a century ago. It seems more and more true that some skeptics, to quote Gavin regarding Dr. Lindzen, are fighting yesterday’s battles. This article brings that comment into detailed relief.

    This is exactly where RealClimate can make a difference, by posting clear, well-developed and well cited explanations in laymans’ terms, which in some cases such as this directly address specific skeptic arguments, and which allow interested “civilians” the opportunity to satisfy themselves that this isn’t all just “guesswork”, and that perhaps there is substantive reason to believe that we can be highly confident of global temperature forecasts.

    Of course, there is still much more ground to cover, such as: how do we know precisely how much CO2 is abosrbed by the oceans; when will saturation occur there; what will the short and long term effect be on climate based on that process. Also needing better explanation: does the planet “react” to the greater presence of CO2 and “make use of it”? In other words, is the carbon cycle expanding? Is that even a coherent question?

    This article is potentially historically important because it sets a tone for further discussion. I can easily envision it as part of a series, a primer which covers the basic issues with regard to AGW and which does so in a simple yet reliable way.

    Bravo.

    Comment by Walt Bennett — 28 Jun 2007 @ 3:19 PM

  80. The problem I have is that a Havard string theorist like Lubos http://motls.blogspot.com/2007/06/realclimate-saturated-confusion.html

    can write a plausible critique of your work and people will accept it because he is a scientist. Now how do I know who is correct? With my lack of qualifications in any of the disciplines how do I know what is the correct science?

    In reading the two articles I do notice one striking difference. The RC article from Spence and Ray includes copious references to other people’s work and includes no implied or otherwise insults to other researchers.

    Lubos on the other hand, as I read it, seems to think that just because he can understand differential equations that he is correct and everyone else is wrong. Lubos in following comments also disparages consensus as being weak however to me other people confirming what you are saying with peer reviewed work is a sign, at least to a layperson such as myself, that you have a greater chance of being correct.

    The radiation budget of the Earth is a very difficult subject and contains many non obvious traps for beginners that I thing even a string theorist can fall into. Just because you understand strings does not mean that the subject of radiation is easy.

    Again thank you Spencer and Ray for your contribution to helping the understanding of science challenged people such as myself. I know which one has the greater chance of containing at least what truth we know of with our present knowledge.

    [Response: Your warm words are very encouraging. Thanks so much. Spencer deserves all the credit for initiating this article,and without his clear prose and historical perspective it would not have been nearly as effective at communicating the things that needed to be said. --raypierre]

    Comment by Ender — 28 Jun 2007 @ 7:29 PM

  81. One reason this debate can be hard to follow is that there’s a lack of explicitness as to what you are and are not arguing. In particular, if I’m reading right, you’re *not* disagreeing with the claim that each additional carbon dioxide molecule makes less of a contribution to warming than the one before (at least, putting aside potential non-linear positive feedbacks unrelated to radiation). Indeed, my Harvard “atmospheric physics” professor explicitly made this claim while lecturing on radiative transfer, so I presume it’s uncontroversial.

    [Response: That's right. That's completely uncontroversial, and the effect is incorporated in every radiation model at least since Manabe, and more probably since Plass. If it weren't for this effect, there probably wouldn't be any habitable planets at all, since modest fluctuations in CO2 would lead to lethal swings in climate --raypierre]

    You *are*, however, disagreeing with the claim that each additional carbon dioxide molecule makes no contribution to warming whatsoever. But is any serious source actually making that argument? Lubos Motl, for example, is not. (Of course, in characteristic “Lubos” fashion, the lack of a concrete disagreement hasn’t stopped him from enthusiastically insulting your intelligence :-D)

    [Response: It's often quite hard to tell just what Motl is saying, and frankly I don't waste much time paying attention to his blog. Others report that he seems to be claiming that the warming effect of CO2 will saturate before long, and that claim certainly resurfaces from time to time among the skeptics community. I myself thought the argument had died out completely, but Spencer reports that on his blog he had been getting repeated questions about saturation. Anyway, it's irrelevant what Motl thinks, since this post is not a response to anything in Motl's blog, regardless of what Motl says. I wasn't even aware that he had written anything about this subject until I saw his blog show up on the Technorati blog-response tracking for our post. --raypierre]

    Comment by Steve — 29 Jun 2007 @ 12:33 AM

  82. Re #68, #72, #77 and others: H2-economy

    Thanks you all for your answers.

    I was not that concerned about explosion hazards: I remember a Dutch study where it was shown that as far as cars were concerned H2 did not have to be more dangerous than gas (= LPG/LNG), which was in use already.

    It seems we have to be more concerned about the destruction of the ozone layer (again) by leaking H2.

    All this quite apart from the fact that H2 is NO energy source and hence no magical cure for our energy problem.

    Comment by Dick Veldkamp — 29 Jun 2007 @ 3:20 AM

  83. #60 “He’s clearly a very smart person, but he should stick to stuff he knows. Typical theorist.”

    And here we have a quote: “Although I consider myself primarily a theoretician…” from none other than our esteemed co-author.
    sorry couldn’t resist!

    [Response: I myself wouldn't describe Motl's distortions as being in any way typical for a theorist. Of course, any good theorist needs to have a very sound understanding of data. I also don't think it's a matter of sticking to things one understands. The kinds of physics we are talking about are easily understood, on a full quantitative level, by anybody with an undergraduate physics degree, or indeed with high-school AP physics. On a sound non-quantitative level, they can be understood more broadly. A person with Motl's background should be able to comment intelligently about these issues, but when somebody with the capability to understand the system fails to do so, there's something rotten in Denmark.

    Somebody earlier raised the question of how to know which authority to believe. It's perfectly valid to look at what institution a person was hired at, and ordinarily being hired by the Harvard physics department should lend some weight to ones opinions about things in physics. Even Harvard makes mistakes, though (and the word on the web is that this particular mistake may be in the process of rectifying itself), so one must look beyond just a person's pedigree. A good place to start is to look at what people have published, in what journals, and how recently. Peer judgment is also worthwhile, so looking at what panels a person has served on is useful. In the end, while some things need to be accepted on authority, there's really no substitute for actually understanding the scientific arguments, and in a democracy, it's incumbent on scientists to try to make the arguments comprehensible enough that one doesn't need to lean too much on pure authority. --raypierre ]

    Comment by Alan K — 29 Jun 2007 @ 5:59 AM

  84. I’m not sure if Lubos isn’t a Sokalian hoax. Has anybody seen him in reality?

    Comment by Florifulgurator — 29 Jun 2007 @ 7:05 AM

  85. My memory and knowledge are fuzzy, but I have a couple of questions on H2-powered vehicles I need clarifying.

    I believe Iceland have had H2 powered vehicles and infrastructure for several years, you could probably check out the problems and solutions they have achieved in the last decade or so. Probably getting a bit off track here to go into any details though, and its not hard to find information on it.

    Comment by stuart — 29 Jun 2007 @ 8:07 AM

  86. Good explanation that even non-scientists can understand.

    I think it’s interesting the contradictory arguments denialists make. On the one hand they say the atmosphere is saturated with CO2 & H20, so no GW, and on the other they say how can something as small as a few parts per million make any difference? I’ve seen denialists who make both arguments simultaneously.

    Then some go on from “GW is not happening” to “it’s happening, but it’s good for us…warming helps agriculture.” They are all over the board.

    Comment by Lynn Vincentnathan — 29 Jun 2007 @ 8:15 AM

  87. “Moreover,the “thinning and cooling” argument — that the brightness temperature depends only on the layer from which radiation escapes to the observer — is absolutely standard stuff in physics. The core of the Sun is some tens of millions of degrees. You don’t see that when you look at the sky, do you? The core of the Earth is several thousand degrees. You don’t see that when you look at the ground, do you? It would be incandescent if you did. You don’t see it because you see radiation at the temperature of the level from which the radiation can escape. It’s that simple. Atmospheric IR is no different. If you are used to the “photosphere” of the sun, just think of what we’re talking about as the “IRsphere” of the Earth.”

    There is one big problem with this concept: the photosphere of the earth contains huge windows from which IR can directly escape from the surface, That is also the reason why deserts cool so fast at night. You can see the surface of the earth in the infrared thermal window.

    [Response: The concept is fine if you apply it in individual wavelength bands. The "photosphere" for 6 micron IR is at a different height from that for 15 micron IR. --raypierre]

    Comment by Hans Erren — 29 Jun 2007 @ 8:47 AM

  88. Re #81 Where Ray wrote:
    [Response: That's right. That's completely uncontroversial, and the effect is incorporated in every radiation model at least since Manabe, and more probably since Plass. If it weren't for this effect, there probably wouldn't be any habitable planets at all, since modest fluctuations in CO2 would lead to lethal swings in climate --raypierre]

    It is not completely uncontroversial. I am arguing that because it is saturated (optically thick) then adding more CO2 will cause the saturation to be closer to the surface. This means that the surface warming due to CO2 will increase in direct proportion to the CO2 concentration, rather than with the logarithm of the concentration as the current models predict.

    Twixt Plass and Manabe, Fritz Moller found “almost arbitrary temperature changes” and that “Very small variations [in water vapour feedback would] effect a reversed sign or huge amplification. We know that the atmosphere does not react in this way.” However, since Moller wrote that, we now know that rapid climate change does happen, and that Venus has suffered a lethal swing in climate!

    Comment by Alastair McDonald — 29 Jun 2007 @ 8:48 AM

  89. Re 80: Ender, I don’t see how there can be any question. Motl may or may not be a brilliant string theorist, but he is not an expert on climate, on infrared spectroscopy or any other field relevant to these studies. I am a physicist, too. You want to know about radiation, I’m your guy. I can get by in discussing semiconductors, the space environment, spacecraft design, manufacture of electronics… Here, I am a rank amateur. The fact that I’m a physicist and have solved the hydrogen atom and harmonic oscillator problems helps. And the fact that I’ve looked at how energy lines in atoms become energy bands in solids has been invaluable in seeing how the behavior of CO2 as a gas behaves differently than a single CO2 molecule. But the point is that I have made a significant effort in recent years to understand these things. I suspect Professor Motl has not. Certainly, it is not reflected in his arguments, which are naive. Science places great value on expertise. The opinions of a scientist usually carry little weight in scientific circles where that expertise does not extend. Motl’s arguments matter about as much as flatulence in a windstorm.

    Comment by ray ladbury — 29 Jun 2007 @ 8:54 AM

  90. PS to my post above…

    If you are looking at the wavelengths, the peaks are at 20 mu-m, 22.5 mu-m and 25 mu-m, which I presume are exactly what you would expect.

    People can check this for themselves.

    [Response: Yes, infrared spectroscopists generally work in wavenumber in units of (1/cm). In the Part II graphs I plotted things as a function of wavelength instead, since I figured wavelength is a more familiar quantity. --raypierre]

    Comment by Timothy Chase — 29 Jun 2007 @ 11:01 AM

  91. RE: #81

    raypierre (and Spencer)

    Steve asked “You *are*, however, disagreeing with the claim that each additional carbon dioxide molecule makes no contribution to warming whatsoever. But is any serious source actually making that argument?”

    Is any serious source actually making that argument?

    I myself do not, but still as climate sensitivity is given in degrees per doubling of CO2, would find it more to worry about the CO2 that is already out there, rather than any we are going to emit in the future.

    Perhaps that’s the point that get oversimplified when people casually suggest that “saturation” has been reached.

    Comment by Maurizio Morabito — 29 Jun 2007 @ 11:08 AM

  92. Alastair, when Ray writes “uncontroversial” I would guess Ray likely means “uncontroversial in published science on the subject” —- why not write the paper you’re promising? If you do the math and do change the opinion of contemporary physics on this question, that will elevate your belief above the many handwaving arguments, political statements, and other opinions that get dropped in here by nonscientists. Without the math, none of those are ‘controversy’ on the scientific question, eh?

    Comment by Hank Roberts — 29 Jun 2007 @ 11:30 AM

  93. Re #88: [we now know that... Venus has suffered a lethal swing in climate!]

    Do we in fact know this? Perhaps I’m quibbling, but I think it’s an interesting question: did Venus in fact experience a “swing” – that is, an extreme change from a perhaps more Earthlike climate – or did it simply evolve towards its present state from its primordial state?

    On the other hand, we do know that Earth once underwent a massive change in atmospheric composition, the switch from a reducing atmosphere to one dominated by oxygen. And what’s more, we know this was caused by the actions of living things. Which should be a good response to the “humans are too puny to affect the whole Earth” line of reasoning :-)

    Comment by James — 29 Jun 2007 @ 12:06 PM

  94. #60, #83, #89:
    When I say “He’s clearly a very smart person, but he should stick to stuff he knows. Typical theorist.” (re. Motl), I am speaking as a theoretical physicist myself. So it’s only a tongue-in-cheek attack on theorists. :)

    There’s a tendency for SOME hothead pencil-and-paper theorists to trivalize physics-related problems outside their own narrow field. You’d be hard-pressed to find an applied/numerical physicist who’d disagree with this.

    Say you have a friend who’s a radiologist. Maybe you ask him/her in private about your heart condition. If you’re friend’s not an arrogant *****, they’ll offer general advice but tell you that you should really ask your cardiologist. Don’t be surprised, though, to find the occasional young brilliant but hothead radiologist who somehow thinks he/she is an expert in other fields of medicine. Same goes for every other professional subfield. Common sense tells you to ignore these people when they are speaking outside their areas of expertise.

    Rad transfer is important in atmospheric physics, astrophysics, nuclear weapons design, and so on. Not string theory. There are any number of experts on radiative transfer, of any political stripe you care to pick. Motl is not one of them.

    Besides, again, he didn’t actually write down the diff eq’s and solve them; he just waved his hands a lot. That might be good for partial credit but it’s not a full answer, sorry. I haven’t solved the transfer myself for this problem either, but I know enough to know what I don’t know (at least in this case), which is more than I can say for Motl.

    Comment by Peter Williams — 29 Jun 2007 @ 12:44 PM

  95. Re #92

    Hank,

    You are quite right! I should have added a smiley when I implied that there was a school of scientists supporting my ideas :-)

    You are also right that I should write my paper, and stop my jousting here. But as Timothy wrote I still have a lot to learn. As Donald Rumsfeld said:

    “There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don’t know. But there are also unknown unknowns.”

    This is a good place to find answers to my unknown unknowns. For instance, if you want to find out why Prof. Ray Pierrehumbert, Goody & Jung, and Einstein were wrong about greenhouse gases radiating according to Planck’s function, then you have to google for the “equipartition theorem” not “Boltzmann distribution” as I had thought!

    Anyway, in the words of Tony Blair may I say to you all au revoir, auf Wiedersehen and arrivederci!

    Comment by Alastair McDonald — 29 Jun 2007 @ 1:08 PM

  96. Re. 86 (Lynn V)
    I am what YOU would call a ‘denialist’. Denialist of what? I happen to be sceptical with regard to the threat of AGW. You use the term ‘denialist’ as if it means the denial of truth. Its true that irrational and arrogant arguments are presented by sceptics. But this is equally true of many AGW advocates. It is wrong to present the irrational arguments as representative of all sceptics. I care about the natural environment as much as you do. I totally support a reduction in use of energy and natural resources (especially water). I support the use of walking, cycling or public transport where possible. I detest 4x4s (SUVs) in urban environements, etc, etc. It seems however that a support of AGW theory has become a benchmark of whether you care about the environment. This is certainly true for Euroepan politicians. However, as a scientist, I am not going to say I believe something just because its ‘popular’ or polictically correct. In contrast to many commentators on this blog, scientific truth is not defined by how many peer-reviewed articles you have published or can quote. Here is an analogy for me. At school you are meant to believe all the teacher tells you and all you read in the text books. These are the ‘experts’. But when you progress to science at university, you are encouraged to understand the arguments and to question, and in particular to not assume that the ‘expert’ writer is always correct. Science would not progress and evolve if we did not question and challenge. When I read a scientific paper or artical, I expect the arguments to be convincing. When I feel they are not, I believe I have every right to challenge the view given. My reasons for scepticism regarding AGW are straight forward:
    1. The view that current temperatures are warmer than at all times in the past 2000 years is unconvincing. IPCC itself highlights the uncertainties regarding evidence from more than about 500 years ago.
    2. The view that temperatures are rising more rapidly than ever (ie. in human history) is unconvincing. The current trend is no more significant than experienced during the first half of the 20th century, when ‘dramatic’impacts what not noted.
    3. Its true that the world is warming and that ice is melting and glaciers receding, etc, but there is nothing to indicate this is anything other than a response to natural changes.
    4. While the current trend does not corelate well with sun activity, the view that CO2 emissions are the ONLY explanation is unconvincing.
    5. Many, many people (including many I know) are convinced that extreme weather is becoming far more common. This is in very large part due to modern communications whereby we routinely see floods, droughts, storms, etc on our TV screens whereas, say 20 years ago, we didn’t. The view that there is statistically increasing trend linked to glbal warming is unconvincing.
    6. Its strange to me that ‘climate change’ is commonly presented as the biggest threat facing mankind. It remains a theory. There are very real problems facing mankind, such as millions dying every year of poor drinking water, malnutrition, malaria and Aids. We could really do more to deal with these. The problem is that they are not problems of the developed world. Climate change seems to be affecting us (although WE argue that its the poorest countries who will be affected most). To me, worrying about climate change is basically self-indulgent. There are truly bigger and more certain problems out there we could do much more to help with.

    And just to return to whether its reasonable to question the ‘consensus’science. If you look at the link I provided in 17, you can view reviewers comments on various IPCC drafts. Now, I would assume all of the reviewers were invited by IPCC on the basis that they are respectable experts who are qualified to comment. If you look at this, you will see many comments that do not agree with the supposed concensus. The final conculsions are not unanimous. While this may represent a majority view, it is incorrect to claim there is no debate and there is complete concensus.

    All the best.

    Comment by PHE — 29 Jun 2007 @ 1:18 PM

  97. Re 86 Lynn Vincentnathan: “I think it’s interesting the contradictory arguments denialists make…. They are all over the board.”

    That’s because they are not at all interested in following where the science leads and basing their conclusion on what it tells them, but in finding every possible argument and data point, no matter how tenuous, to support the conclusion that they have already made, namely that it is not happening. As a result they keep latching on to factoids such as the warming on Mars, or the increased reflectance of Pluto, or the 800 year CO2 lag, or CO2 saturation without critical thought.

    I’ve encountered exactly the same process in non-scientific controversies. Not only are the same type of self-authoritative, tautological, straw-man and red herring arguments used, but more important, when a number of diverse people who have in common only their opposition to some thing or other coalesce solely to argue or fight against it they almost never can agree with each other on what they are for. When asked to propose an alternative idea or course of action they instead begin to argue amongst themselves. While they are fighting the fight, the contradictions simply don’t matter, kind of in the “the enemy of my enemy is my friend” way.

    Comment by Jim Eager — 29 Jun 2007 @ 1:22 PM

  98. Document http://www.metoffice.gov.uk/climate/uk/about/UK_climate_trends.pdf gives the observed Trends in the UK climate.

    It is a very good document, easily understood and is of the highest quality.

    It shows quite clearly that the climate of UK is changing, and some of the parameters measured are unprecedented in the series recorded.

    In particular sunshine amounts and temperature show a matching upward trend from 1987 (fig 3 and fig 15)and both have reached record unprecedented levels at the end of the series in 2003/4. And my subjective observations are that the Matching Trend continues upwards for 2005/6.

    The exact correlation between sunshine amounts and temperature, region by region, is so perfect that I have had to read it several times to make sure I wasn’t making a mistake.

    The scientific consensus is that this observed warming of surface temperature in UK is due to secondary infra red absorption/excitation of a tri-atomic molecule ( CO2) high in the Troposphere, and that the direct warming caused by the extra sunshine is not important, I find it difficult to fit this consensus view with the actual observations.

    If there are less clouds, this must be a strong indicator of less moisture (water vapour) in the atmosphere, which would reduce the greenhouse effect and so we should actually be getting colder.

    The report only says that the observed results match the models, but does not go any further and tell us what model and why it fits, and says further work will take place on analysing inter-relationships.

    Can anyone help and explain why the simple prosaic reason is that its getting warmer because its getting sunnier is not the consensus view!

    Comment by john — 29 Jun 2007 @ 1:48 PM

  99. re #96:
    As a matter of principle, I admire the type of skepticism you describe. I personally tend to think the situation is rather dire, but I’m not an expert either – although I have been impressed with the scientific articles I have read on the subject in Science and Nature, I must say.

    Matters of science and matters of policy are not one and the same, though. The sane person, when confronted with reasonably substantial evidence that he/she has a life-threatening illness, does not wait until a complete scientific consensus before seeking treatment.

    Come on, if we applied the same risk analysis to GW as we did to, say, terrorism (e.g. the famous 1% doctrine) we’d have begun mitigating this decades ago. It is a reasonable stance, even if you are leaning towards skepticism, to support anti-GW legislation now instead of later. I don’t like political litmus tests either, but I don’t think this is an unreasonable one as such things go.

    Comment by Peter Williams — 29 Jun 2007 @ 2:24 PM

  100. Regarding the IPCC AR4 WG1 Report and the Consensus

    The best the “contrarian” organization Heartland Institute could come up with as criticism of the IPCC WG1 AR4 was a comment by RealClimate’s Eric Steig:

    Al Gore Confronted by Own Scientists – ‘Confusion Between Hypothesis and Evidence’
    Posted : Thu, 28 Jun 2007 21:20:00 GMT
    Author : The Heartland Institute
    Category : PressRelease
    http://www.earthtimes.org/articles/show/news_press_release,131357.shtml

    It is obvious that Eric agrees that climate change is a serious issue and a serious threat. At the same time, he wanted the report to be bulletproof so that it could be taken seriously by fellow scientists as an undistorted product of the best science available at the time. I am not sure that he was entirely happy with it, but that was the final draft and they presumably incorporated many of his suggestions.

    With a document this large and with as many head-strong highly intelligent individuals that were involved, there are bound to be differences. The IPCC asked for criticism from those individuals. They got it, and in many cases (at least where what was being asked for didn’t result in the document becoming much more lengthy than it already was), they took that advice, and as a result the report was made that much stronger.

    Is everyone happy every sentence and every word? Obviously not. But the consensus is there for every piece even when a minority disagrees on one point or another. And the consensus is strong. The consensus wasn’t created by the report, but highlighted by it – for the purpose of countering propaganda by special interests.

    Moreover, the honesty of the process itself is highlighted by their openness and transparency in making available the criticisms which guided the final editing of the report.

    Comment by Timothy Chase — 29 Jun 2007 @ 3:04 PM

  101. [[In particular sunshine amounts and temperature show a matching upward trend from 1987 (fig 3 and fig 15)and both have reached record unprecedented levels at the end of the series in 2003/4. And my subjective observations are that the Matching Trend continues upwards for 2005/6.
    The exact correlation between sunshine amounts and temperature, region by region, is so perfect that I have had to read it several times to make sure I wasn't making a mistake.
    ]]

    I think you may be conflating sunshine received at the ground with solar output, which isn’t necessarily a one to one relationship. We’ve been measuring solar output from satellites since the 1960s, and continuously since 1979, and it just hasn’t increased enough to explain the current global warming.

    Comment by Barton Paul Levenson — 29 Jun 2007 @ 4:07 PM

  102. re: #96

    thank you PHE for posting such a reasonable comment. I have still to understand why people cannot tolerate nuances about GW, and if somebody dare suggest he/she is yet to be convinced, there come the cries of “denialist” and “contrarian”.

    re: #98

    John: I think it’s still too difficult to understand climate variations at regional and country level. For example I would be surprised to hear that clouds in the UK are only made out of local moisture. If there are fewer clouds, somehow the Atlantic weather fronts have changed, in intensity, duration or direction. I don’t think the Met office document mentions that? As a matter of fact, the NAO changed in 1989. Perhaps that’s just a coincidence.

    ========

    The difficulty with climate science as it stands now is that there’s only so much you can squeeze out of models, and especially global models. And so despite all the “consensus”, the discipline looks dead in the water.

    If the G8 countries will tackle CO2 the way they have tackled drug trafficking and world poverty, there is no danger of any success whatsoever…

    We need climate science to make local models making local predictions in the timescales of months, to compare to actual observations of the now instead of vague terrors of the 2050′s. Otherwise the whole GW business will remain a shot in the dark: a reasoned shot, but still pretty much in-the-dark.

    On the other hand if we finally could see some BIG change such as hurricane seasons in the south Atlantic, sustained rain in the Sahara or the Atacama desert, or anything else of truly historical magnitude, there would be a much stronger convincing argument. Time will tell.

    Comment by Maurizio Morabito — 29 Jun 2007 @ 4:22 PM

  103. PHE
    If you seek to avoid the “denialist” label, there are some important things you can do to not look like a denialist (maybe we need Jeff Foxworthy here, “If you can simultaneously argue that the small amount of CO2 in the atmosphere makes it impossible as the cause AND that CO2 is saturated… you may be a denialist….”)
    First and most important, NEVER think that calling something a THEORY trivializes it. Gravity is a theory, but she is also a harsh mistress. Relativity is a theory, but there are >100000 Japanese who would attest to its truth had they survived the attack of the Enola Gay and so on. Dismissing something as a “theory” will damage your credibility in scientific circles faster than saying “Waddup, Ni—-…” at a hip-hop concert.
    Second, if you are going to make a claim like “…the view that CO2 emissions are the ONLY explanation is unconvincing,” it would be helpful for you to list some proposed candidate explanations. That way it appears as if you have actually done your homework and looked into the subject and not just said “There must be something…”
    Third, similar considerations apply to your claims that the warming we are experiencing is neither rapid nor dangerous.
    Finally, the climate change issue must be a good thing, right? I mean look how many people have discovered a new-found interest in the plight of poor African and Indian peasants. Now PHE, you may be sincere in your interest in the poor, but your contention that we must address EITHER climate change OR these other issues is false. We will not resolve climate issues unless we provide a path for developing nations to address these other issues without increasing greenhouse gases. And, climate change is likely to exacerbate most of these issues, so they cannot really be addressed separately from climate. So, rejoice PHE, you can have your humanitarian causes AND accept the scientific evidence, too.
    A true skeptic has reasons for his skepticism that could be resolved with the right evidence. What evidence do you require?

    Comment by ray ladbury — 29 Jun 2007 @ 4:32 PM

  104. First, John, reduced clouds do not necessarily mean less water vapor. Clouds form when the humidity rises above 100%–either due to increasing water vapor or decreasing temperature. Second, of course more sunshine means higher temperatures: Sunlight dominates the energy budget of Earth. To see the effect of greenhouse it helps to go where the influence of the Sun is diminished–the poles, night time, Winter. All these are warming even faster that other places/times. Don’t confuse local sunny weather with global trends. Overall, solar output isn’t changing enough to account for the observed changes.

    Comment by ray ladbury — 29 Jun 2007 @ 4:51 PM

  105. >solar
    Is this current info? It’s a very small amount per decade.
    http://www.space.com/scienceastronomy/sun_output_030320.html

    “… Sun’s radiation has increased by .05 percent per decade since the late 1970s.
    “The increase would only be significant to Earth’s climate if it has been going on for a century or more, said study leader Richard Willson, a Columbia University researcher also affiliated with NASA’s Goddard Institute for Space Studies…”
    http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=solar_radiation_030320_02.jpg&cap=The+recent+trend+of+a+.05+percent+per+decade+increase+in+Total+Solar+Irradiance+%28TSI%29+in+watts+per+meter+squared%2C+or+the+amount+of+solar+energy+that+falls+upon+a+square+meter+outside+the+Earths+atmosphere.+The+trend+was+measured+between+successive+solar+minima+that+occur+approximately+every+11+years.+At+the+bottom%2C+the+timeline+of+the+many+different+datasets+that+contributed+to+this+finding%2C+from+1978+to+present.

    NOTE the numbers on the X-axis, rather than proclaiming this proves the sun’s responsible for anything comparable to current rate of change, fellow readers.

    Comment by Hank Roberts — 29 Jun 2007 @ 5:39 PM

  106. In comment 78 Rod B. asks,

    doesn’t the H2 need to be manufactured on board as needed from hydrocarbons, and isn’t that process currently too slow, energy intensive, and cumbersome for that? If pure H2 is stored (in liquid form??) on the vehicle it seems the fire/explosive hazard would be prohibitive, but, more significantly, wouldn’t the “gas tank”, to handle the high pressure, need 2-4 tons of thick high-grade steel? Wouldn’t all of this make H2 a non-starter? Or am I way behind the times and science?

    In reverse order … No; H2 has been a non-starter for about 35 years now. (Put the mouse cursor on the “Cars” button, then select the “1807-1999″ menu item.)

    If hydrogen is stored on board as liquid, then the only pressure involved is its vapour pressure, which is just 1 atm at 20.28 K. A typical tank for liquid has a relief valve that lets gaseous hydrogen out at 4 bar. It goes to a fuel cell that promptly oxidizes it, preventing an explosive buildup. The time it takes for the pressure to rise from 1 atm to 4 atm is several days, much longer than a motorist is likely to wait, so usually there would be no venting. Rather, quick withdrawal of the vapour would drop the temperature below 20.28 K, and vapour pressure would no longer help the fuel come out; so there’s actually an electric heater to prevent that.

    Because the pressure is not high, such tanks, while they are heavy, aren’t any two tonnes. One such tank has an empty mass of 145 kg, full 154.5 kg. Much heavier than an equivalent full gasoline tank.

    Hydrocarbon on board, reformed to hydrogen? No; that would be ridiculously inefficient compared to just burning the hydrocarbon. Not that it hasn’t been tried, though, and that such a stupid thing would be tried strongly suggests recent hydrogen-car efforts were a deliberate waste of researchers’ time. (Fuel cells in FCEVs are not efficient compared to internal combustion motors burning the same fuel. The efficiency advantage, being negative or, ideally, zero, does not make up for energy lost in chemical processing of hydrocarbons, on-board or elsewhere.)

    Comment by Burn boron in pure O2 for car power — 29 Jun 2007 @ 5:40 PM

  107. Re 101, 102 and 104,

    Thanks for replying, the increase in sunshine amounts in UK is staggering some 20-40% in Winter, 5-10% in summer, etc. over the last 40 years. The maps at end of report really are an eyeopener.

    This tendency to clear skies is observable even at the subjective man in the street level, which is where I started, after the sunniest and warmest April on record, there was hardly a cloud in the sky all month. For a resident of UK this is unprecedented we are used to cloudy overcast skies.

    It isn’t being talked about by the Climate Scientists/ Meteorologists in UK, even though it is an unprecedented fact.

    More direct sunshine reaching the surface must mean higher observed surface temperatures because that is what we are measuring. I know its boring and not very exciting but that is what is happening in UK. I could also envisage that all this extra direct sunshine might impart extra energy into the surface climate, particularly the oceans, and “liven” things up a bit, so you might get some unprecedented extremes.

    Comment by john — 29 Jun 2007 @ 5:54 PM

  108. #103 – That’s a tired old misnomer. Gravity is not a theory, it’s an observable phenomenon. The string theorists are still arguing over the theory of gravity, and there’s no “consensus”. Just because there’s no consensus on the theory of gravity doesn’t mean that things don’t fall down. Go over to Motls if you want to learn something about current state-of-the-art gravity theories, but don’t expect any consensus, because there isn’t one. Even if there were a consensus, that doesn’t guarantee that it’s right. How many centuries did we have a consensus that the sun orbited the earth?

    There’s an analogy here wrt global warming, with the added problem that the observable phenomenon itself is a lot more ambiguous than watching the sun come up in the morning.

    Comment by Lurker — 29 Jun 2007 @ 5:54 PM

  109. Lurker, note that I didn’t mention any specific theory of gravity. I said gravity–as in the force between two objects with mass. And yes, it is a theory. Evolution is a theory. Conservation of energy is a theory (and yes, physicists considered giving it up only 80 years ago when confronted with beta decay–instead they postulated the neutrino).
    There is nothing ambiguous about climate change if you live in the arctic of on the pacific islands. There’s nothing ambiguous about it if you look at data from Icesat. There’s also nothing ambiguous about the basic physics. Climate change is a reality, and if you think we aren’t causing it, maybe you can suggest where all that energy is coming from.

    Comment by ray ladbury — 29 Jun 2007 @ 6:07 PM

  110. Burn pure – The liquid H2 scheme that you propose would be practical for commercial vehicles, but for private transportation, when you use it for 1-2 hours out of the day or less, the losses due to venting will make it forever impractical. Your name seems to imply an alternative energy medium scheme, and whether it’s B-O2 or some alternative, I think where we will be in 50 years is with something other than H2. There are, as your name suggests, alternatives.

    I also expect to see fuel cells in commercial vehicles first, and we may never see them in personal vehicles, for similar reasons. Not without a breakthrough in cold fuel cell chemistry, anyway. But microturbine hybrids will be slightly less efficient, and we almost know how to build them now. But I do think that over the 30-50 year horizon, the only hydrocarbon fuels may end up being biofuels for niche applications.

    Comment by Lurker — 29 Jun 2007 @ 6:13 PM

  111. Re #106: [If hydrogen is stored on board as liquid, then the only pressure involved is its vapour pressure...]

    Am I missing something here? Or forgetting those long-ago chemistry lessons in which I seem to remember learning that the critical point of H2 is somewhere around -400F, therefore it can’t be a stable liquid near ambient temps at any pressure? That the only way to keep for any length of time at all is in a good dewar flask? So you leave your liquid H2-fueled car e.g.parked at the airport while you go on a long trip, and come back to find that all your fuel has evaporated :-(

    Then there’s the other side of the equation: the amount of energy needed to cool H2 to a liquid, none of which (AFAIK) is recovered when it vaporizes.

    Comment by James — 29 Jun 2007 @ 7:14 PM

  112. As mentioned, the Magna-Steyr tank I had in mind weighs 145 kg empty. Much of that mass is because it is, in fact, a good Dewar flask — a tough one that, I seem to recall, has passed crash tests.

    As mentioned, “any length of time at all” is in this case a few days before venting begins, and I suppose a few weeks before it’s all vented. It is catalytically oxidized as it comes out. One could indeed find one’s car inert in the airport carpark on return from a long trip. There would presumably be a big parking bill also.

    Another poster seemed not to understand that normal use would, by reducing the pressure in the vapour space in the top of the tank, knock the temperature back down, so an ordinary driver would use up all the hydrogen he bought and never let the relief valve take any.

    [Response: Look, guys what the heck does the hydrogen economy have to do with radiative transfer? Unless you want to relate this specifically to radiative effects of H2, please stop. That goes for the off-topic and rather confused thread going on about UK cloudiness as well. If this discussion doesn't move back on-topic soon, I'm going to have to close down the thread. Probably about time to do that anyway. --raypierre]

    Comment by Burn boron in pure O2 for car power — 29 Jun 2007 @ 7:46 PM

  113. As long as we are so far off-topic to consider alternate transportation energies, I’ll suggest using bio-oils in a gas turbine. The bio-oils are obtained by pyrolysis of essentially any form of bio-mass, so the production of the bio-mass need not compete with growing food and animal feed.

    I’ve previously attempted to provide, again, a link to a useful site, which is working again now, but somehow the filters catch it. Instead, I’ll suggest web trawling on the search term “Shimbir Demon biochar”…

    Comment by David B. Benson — 29 Jun 2007 @ 8:21 PM

  114. #98,101
    I don’t agree that the points made in #98 are supported by the document http://www.metoffice.gov.uk/climate/uk/about/UK_climate_trends.pdf.

    If you read it carefully, the increase in annual sunshine hours is mainly in the autumn/winter months and is attributed to the Clean Air Acts.

    Domestic coal fires used to be one of the main causes of fogs in urban areas, which happen during still anti-cyclonic conditions in cold air.
    Since the 70′s smokeless fuel and gas have replaced coal fires, so the amount of winter fogs has decreased and days that might have remained foggy end up with bright sunshine.

    There’s no real evidence this is anything more than a localised phenomenon, or that it’s correlated with rising temperatures.

    Comment by Alex Nichols — 30 Jun 2007 @ 1:07 AM

  115. Its my impression that nobody wants to take an objective look at all data and make assumptions on what the trends appear to show. Any mathematical model developed in this world was based on Calculus and acceptable errors: STATISTICS in the end. Newton’s law of gravity was based on a best fir line with acceptable error. But several have reported that Newton did through away outliers, which can be scientifically taboo. Nevertheless, it’s a mathematical model, just some work better than others.

    Comment by Robert Jacobs — 30 Jun 2007 @ 2:04 AM

  116. Charles Lyell (#115) wrote:

    Why don’t we deal with the root problem nobody wants to address: OVER POPULATION.

    The population is going to level out around 11 billion, last I heard. Population growth has been decelerating since the 1980s. The big question at this point is how do we get enough energy to support that many people without wrecking the climate.

    The way things are going right now, the glaciers of the Himalayas will be gone by 2100 causing massive water shortages directly affecting over a billion people and drastically reducing agricultural output in Asia, agriculture will have virtually been wiped out in the United States around the same time, and water levels may very well rise several meters in the interim – with about half of humanity living within fifty miles of coastline. The damage to the world economy will in all likelihood be unprecedented – and well before the end of the century – unless we start doing something about climate change soon. And it has to be soon, because we are beginning to set in motion processes which will take on a life of their own.

    Comment by Timothy Chase — 30 Jun 2007 @ 3:58 AM

  117. Re #113 no significant dent in Oil consumption will be made until second generation biofuels are successfully conquered, then maybe we can make a dent in oils CO2 emissions. Th USA has just this week allocated $275 million to this very task but although it seems easy it reckon it will take a decade or two before this technology is viable.

    Comment by pete best — 30 Jun 2007 @ 4:27 AM

  118. Re #109, I do not know what you mean by the term theory but in scientific terms in means a law or model of reality. There is confusion here as laid out by lay people as theory means talking nonsense but in scientific parlance it has a totally different meaning.

    Evolution is a model of how organisms evolve and through genetics we now appear to have the mechanisms of how they do it to.
    Gravity, Einsteins special and general relativities are models of how gravity works.
    Conservation laws, again a model of how matter and energy interact.

    Simple really.

    Comment by pete best — 30 Jun 2007 @ 5:38 AM

  119. [[Gravity is not a theory, it's an observable phenomenon. The string theorists are still arguing over the theory of gravity, and there's no "consensus". Just because there's no consensus on the theory of gravity doesn't mean that things don't fall down. Go over to Motls if you want to learn something about current state-of-the-art gravity theories, but don't expect any consensus, because there isn't one.]]

    Yes there is. Gravity is a result of the warping of space as described by general relativity, the best-tested theory of all time. A theory is as good as it gets in science; thus gravitational theory, quantum theory, theory of relativity. Saying a scientific consensus is “only a theory” is a sure sign of pseudoscientific belief. I think it originated with the creationists.

    Comment by Barton Paul Levenson — 30 Jun 2007 @ 5:58 AM

  120. Re;114

    So what you are saying is that it is not getting warmer because of the extra sunshine, for whatever reason we have extra unprecedented amounts of sunshine, but you want me to believe this is not affecting the measured surface temperature. Which is where I started I don’t understand this view.

    I have no theory on why this is happening, it just is.

    We maybe need a climate scientist or theoretical physicist to say why we have extra sunshine, I think I can work out that extra sunshine amounts will substantially explain why the recorded average surface temperature in UK has gone up, I only have to walk out the front door.

    Comment by john — 30 Jun 2007 @ 6:39 AM

  121. John, try an analogy,

    —- imagine you’re standing in an empty swimming pool and someone’s running a hose pointed into the swimming pool.
    Meanwhile, outside, someone’s slowly closing the drain valve.

    Sometimes your head gets soaked —- if you happen to be standing under the hose. You may believe more water is coming in.
    It seems obvious, from your position.

    Other times your head gets dry — if you happen not to be standing under the hose. You may believe less water is coming in.
    It seems obvious, from where you’re standing, looking up.

    But all the time, the water’s slowly rising around your ankles.

    Same with sunshine —- the amount coming in from the sun hasn’t changed greatly. 2 or 3 out of 1300, reading the charts.

    What’s changed is how much is going _out_, overall, total, from the pool. That’s why the water’s rising.

    Comment by Hank Roberts — 30 Jun 2007 @ 8:42 AM

  122. Tim #100
    “Moreover, the honesty of the process itself is highlighted by their openness and transparency in making available the criticisms which guided the final editing of the report.”

    It is my understanding, and please correct me if I am wrong, that past IPCC policy was to provide the review comments only to authors/commentators, and that the comments were not to be distributed or published. What happened here is that government agencies that participated in the report and had the comments were hit with freedom of information requests to release the comments. Faced with certain release through that mechanism, IPCC relented and published the comments. Open and transparent has not been part of the process up to this point. I will leave judgment of the character of the comments and responses to those that have read the full review comment and response document.

    Comment by Sam — 30 Jun 2007 @ 8:54 AM

  123. An FYI :
    Found: The Clearest Ocean Waters On Earth

    Raimbault made another surprising discovery: the patch of the ocean that is poorest in life appears to be extremely rich in dissolved organic carbon.

    He is currently teasing apart data in an attempt to explain the apparent contradiction, but believes it may be that the limited availability of nutrients such as nitrogen and phosphorus means the bacteria that would normally degrade the dissolved organic matter are not able to complete the task.

    Story Here

    Comment by COLORADO BOB — 30 Jun 2007 @ 8:55 AM

  124. re 106 (BBIPO2…..) Thanks for the info.

    How do you get liquid H2 without high pressure and/or really low temperatures?

    Haven’t seen your posts for awhile…

    Comment by Pod B — 30 Jun 2007 @ 10:19 AM

  125. Rre 125 clear ocean
    I don’t know what this story has to do with the topic of this thread, but it is really not very suprising for the reason mentioned – open ocean food chains are not usually limited by dissolved organic carbon.

    Comment by Chuck Booth — 30 Jun 2007 @ 10:20 AM

  126. re 123

    Hank I give up, you seem to be able to see things I can’t.

    The Temperature Graphs Start At 1914 the sunshine at 1929, the maps normalise it all from 1961 to 2004.

    The warmest year occurred in 2003 which was also the sunniest

    Comment by john — 30 Jun 2007 @ 10:25 AM

  127. re 115: [... Humans are the only species that continue to reproduce while resources disappear....]

    That’s simply fallacious prima facie. How on earth does the hound cognitively decide he’s running low on Alpo and had better not impregnate that cute little in heat hound today??

    Comment by Pod B — 30 Jun 2007 @ 10:35 AM

  128. #re 123 and previous comments

    I think he’s trying to reintroduce the cosmic-ray argument by the back-door, but there’s absolutely no evidence that this is anything other than a local U.K. phenomenon

    Even the data he’s quoted doesn’t support the argument.
    For instance, Northern Scotland is reported as having a slight fall in average annual temperature, but an increase in recorded sunshine.

    (By the way, the paper is unpublished and has dropped off the server)

    As an example of why this idea just won’t work, here’s some data from Cambridge NIAB for June and July.

    June
    yyyy tmax tmin Sun hours
    1959 21.6 10.1 252.4
    1962 19.6 8.0 289.6 *
    1969 19.4 8.6 268.7
    1976 24.5 11.4 277.8 ~
    2006 22.5 11.2 220.2

    July
    1959 23.9 12.2 270.7 *
    1962 19.4 11.0 126.4 +
    1995 25.8 13.4 234.9
    2006 28.3 14.1 253.5 ~

    * heighest sunshine total
    + lowest sunshine total
    ~ warmest

    Notes:-

    June ’62 was sunnier, but much cooler than June ’76
    July ’62 also had less than half the sunshine of the preceding June, but was warmer, due to higher night time temps)
    July ’06 is by far the warmest month, but has less hours of sun than July ’59.

    Comment by Alex Nichols — 30 Jun 2007 @ 11:19 AM

  129. Re #112: [One could indeed find one's car inert in the airport carpark on return from a long trip. There would presumably be a big parking bill also.]

    Whereas I’ve left my Insight hybrid parked (though not at the airport :-)) for months at a time while away on trips, and it starts right up with no fuel lost, and no obvious battery decay.

    If you look at everything that goes into a hydrogen economy, you find that it’s a real non-starter. I think the only reason the idea ever became popular was as high-tech “pie in the sky” that let certain powers-that-be give the impression of doing something while in fact continuing with business as usual.

    Comment by James — 30 Jun 2007 @ 11:47 AM

  130. Why the IPCC Released the Internal Comments

    Sam (#124) wrote:

    Tim #100
    “Moreover, the honesty of the process itself is highlighted by their openness and transparency in making available the criticisms which guided the final editing of the report.”

    It is my understanding, and please correct me if I am wrong, that past IPCC policy was to provide the review comments only to authors/commentators, and that the comments were not to be distributed or published. What happened here is that government agencies that participated in the report and had the comments were hit with freedom of information requests to release the comments. Faced with certain release through that mechanism, IPCC relented and published the comments. Open and transparent has not been part of the process up to this point. I will leave judgment of the character of the comments and responses to those that have read the full review comment and response document.

    A fair hypothesis.

    However you yourself have just given good reason to discount it.

    Surely contrarians have insisted that they had the right to such information in the past – as they could have mined it for mud to sling at the report itself, much like creationists will dig-up material from the 1930s regarding earlier controversies in evolutionary biology which have long been settled and only tell what parts suit them. But the IPCC did not release the information on those earlier occasions now, did it? You said so yourself. And surely Exxon would have requested such information if it thought that it had any chance of obtaining it for the purpose of selective quotes and the slinging of mud – but they realized it would have made them look foolish.

    Therefore one can only conclude that the IPCC is under no obligation to release the internal comments, and that the Freedom of Information which exists in some countries is non-binding on the IPCC.

    However, rather than relying upon such logic, I went ahead and performed a search on both Google News and the Google News Archives using the two phrases “freedom of information” and “international panel on climate change.” Nothing on the first, two identical hits on the second, niether of which were relevant.

    Nothing.

    No doubt the contrarians will find more “dirt,” but at this point all that the contrarian Heartland Institute has found that they thought they could use as “dirt” is RealClimate contributor Eric Steig’s criticism – which they conveniently edited in a highly selective manner.

    And as I stated above with respect to Eric Steig’s comments:

    It is obvious that Eric agrees that climate change is a serious issue and a serious threat. At the same time, he wanted the report to be bulletproof so that it could be taken seriously by fellow scientists as an undistorted product of the best science available at the time. I am not sure that he was entirely happy with it, but that was the final draft and they presumably incorporated many of his suggestions.

    He illustrates the honesty and integrity of the participating scientists that went into the process.

    Some of the authors had gotten overly enthusiastic in their claims and he called them on it, specifically with respect to the suddenness of catastrophic climate change. It may very well be the case that things can occur that quickly – but we do not as of yet have the evidence required to claim the degree of justification they wished to claim. So as a matter of honesty and as a matter of upholding the integrity of the science he was blunt. Yet at the same time he pointed out what he thought was right in the sections which he commented on.

    The IPCC released the comments in large part due to its recognition of the urgency of our present situation and their recognition that the science is strong enough to justify acting in recognition of this urgency, not due to legal issues. They realize that the best way of communicating this urgency is by being transparent and releasing the comments – despite the fact that they would be providing contrarians with potential material to sling at the report.

    In any case, I wish to thank for giving me the opportunity to clarify the nature of their decision and underscoring the need for such clarification.

    Comment by Timothy Chase — 30 Jun 2007 @ 1:29 PM

  131. First of All,

    I sent in plenty of comments using my name and email account way before this started and I still don’t see anything posted. You blocked my access to the site. Right before you Shut down my internet access and attacked my computer. But you didn’t know the other names, amazing how they got through.

    Now you don’t post this and my point taken.

    Would you guys like to see my Firewall log or let’s go even deeper and I’ll get my internet provider involved. I wonder how the scientists represented on this website would feel about this.

    You still don’t talk about the science, WHY?

    You present yourselves as a science discussion forum, but for the past 2 days all you were concerned about is defacing and smearing two scientists that want to make a difference in this world. Well good luck with that; hope all that works out for you!.

    [Response: Frankly, I have no idea what you are talking about. You have posted under at least three different names from the same Colorado IP address and posted almost identical content from other nearby locations, and on one occasion from alaska (good one!). I searched the logs and can't find any comments under your name prior to this thread. You are welcome to continue to post, but this kind of whinge is not particularly constructive. Your paper has been criticised because it correlates two time series that are dominated by strong linear trends without any mechanism or any appreciation for the actual state of the science. If you want to defend that, go right ahead. If you want to stoke your persecution complex, please go elsewhere. - gavin]

    Comment by Edward H. Moran — 30 Jun 2007 @ 1:47 PM

  132. Good Point Gavin,

    But CO2 and temperature also show linear trends, Isn’t that what we’re concerned about?

    Comment by Edward H. Moran — 30 Jun 2007 @ 4:04 PM

  133. Tim – You are welcome. I was glad to give you the opportunity to clarify and underscore the need for the clarification.

    Comment by Sam — 30 Jun 2007 @ 4:11 PM

  134. Please, everybody, stick to the topic or I’ll close down the thread. Why do people feel the right to start the silly season on every article when we get past comment #100 or so? If we’re out of things to say about the topic, it’s time to just move on anyway.

    Comment by raypierre — 30 Jun 2007 @ 5:06 PM

  135. Edward H. Moran, I am sorry if you were offended by the appellation “nutjob”. As a physicist, many times in the past, I have been handed a dog-eared manuscript (and yes many were written in longhand) whose author claimed that it “disproved” relativity or some equally well established area of physics. Almost invariably, I have found that the writing of the piece was motivated by the same thing that caused its failure: the author did not understand the science behind it. I have tended to refer to such monomaniacs–many of whom were sane in every other way–as nutjobs. I do not offer any excuses and I do apologize.
    I have provided fairly detailed criticism of your paper elsewhere. I reiterate here:
    1)The reference section is extremely weak. None of the climate references (other than the databases) dates after 1979! The references for geomagnetism are even worse–a single reference to a freshman physics text–and that reference is irrelevant for the geodynamo.
    2)The interpretation of the statistics is completely incorrect. To state that a R^2 of 0.792 “explains” 79.2% of an effect is just flat wrong. All it says is that two variables are weakly correlated, and that correlation in no way implies causation or if there is causation which way it acts.
    3)You propose no physical mechanism for your purported cause–and indeed it is difficult to imagine such a mechainism.
    4)To achieve even the weak level of correlation you demonstrate, you introduce a completely ad hoc, adjustable parameter–unmotivated by any scientific argument.

    These weaknesses would have been sufficient to cause me to recommend that the paper be rejected.
    Now, add to that fact that you short-circuit the normal peer review process and have the paper published in an on-line journal, where your co-author is on the editorial board. The journal in question is NOT a climate journal, or even, as near as I can tell, a science journal. There is no evidence I have found that any of the editorial board possesses any expertise in climate science or any related field. Yet the journal claims to be a peer-reviewed journal, and the paper is published as a regular paper and not an editorial. Then we start seeing the article being promoted on various climate-related websites under various aliases–many of which it appears turn out to be…you. You come on here alleging character assassination and censorship–not behavior that usually generates a good first impression.

    Again, I apologize for the nutjob reference (actually, what I did was lump you in with the nutjobs). However, I hope you can see that your behavior in this matter might be characterized as less than exemplary for a scientist.

    Comment by ray ladbury — 30 Jun 2007 @ 5:09 PM

  136. Raypierre–I agree, but I saw this after I posted. Please feel free to move my comment to the curve manipulation post where it would be appropriate, or just forward it to Ed Moran. And needless to say, I won’t jump down your throat if you don’t publish this or the other. Ray

    Comment by ray ladbury — 30 Jun 2007 @ 5:12 PM

  137. Edward H. Moran (#134) wrote:

    Good Point Gavin,

    But CO2 and temperature also show linear trends, Isn’t that what we’re concerned about?

    How odd.

    This doesn’t look at all linear to me:

    http://www.answers.com/topic/co2-temperature-plot-png

    Highly correlated – as one would expect from two variables between which there exists strong positive feedback, but not at all linear.

    Wait a second – that was plotting temperature and CO2 against time for the past 400,000 years. If we plot temperature against CO2, then we get the following:

    http://home.scarlet.be/~ping5859/correlation.html

    You are quite right – that does appear to be quite linear – and it doesn’t require any unidentified ad hoc polynomial function (#242) to make it work, either.

    Comment by Timothy Chase — 30 Jun 2007 @ 5:15 PM

  138. raypierre (#134) wrote:

    Please, everybody, stick to the topic or I’ll close down the thread. Why do people feel the right to start the silly season on every article when we get past comment #100 or so? If we’re out of things to say about the topic, it’s time to just move on anyway.

    I am hoping that we can get back to the topic. Besides what is currently being discussed with Mr. Moran would seem more appropriate to other recent threads, and while it is less demanding, it also seems less rewarding.

    Comment by Timothy Chase — 30 Jun 2007 @ 5:21 PM

  139. #128 Sorry if this is regarded as an off topic sub-plot but:

    erratum: “Northern Scotland is reported as having a slight fall in average annual temperature, but an increase in recorded sunshine.”

    Sorry, the document was unavailable when I wrote that. Of course it’s the other way round N.Scotland annual sunshine total -5.6% since 1929. Annual temp increase since 1914 is 0.37C.

    All UK regions show warming trend!

    Comment by Alex Nichols — 30 Jun 2007 @ 6:08 PM

  140. Some questions for the authors…

    1. I understand that the absorption of energy is roughly linear for peaks far from saturation, roughly proportional to the square root as one begins to approach saturation, and logarithmic when the peak itself is nearly saturated. However, I would assume that this can be all described by a single function for which the linear, root and logarithmic behavior are only good approximations over certain ranges. Does this function differ from gas to gas? Peak to peak?

    2. When the bands are narrow at low temperatures and low pressures, essentially what one has are well-defined spikes. When bands are broad, there is a range over which a given band is able to absorb. With those who are less acquainted with the greenhouse effect (including myself) I have noticed a certain difficulty in understanding how a narrow peak is able to be so effective in amplifying infrared. For example, near the ground, water vapor has a fairly broad main band. In the stratosphere, carbon dioxide has a fairly narrow main band, yet the effectiveness of the main band of carbon dioxide is within the same order of magnitude as that of water vapor.

    How can this be the case?

    What I noticed with the later paper is that the broad bands actually still consist of spikes, but a great many narrow spikes. Is this part of the key? Is it that each of the smaller spikes are less effective than the centerline of the broad band when it is not saturated, but there are more of them?

    3. The diagrams (which are logarithmic along the absorption factor axis) show the smaller spikes as always being there. Are they, or are they themselves a function of the saturation/temperature/pressure?

    4. Eli Rabett mentioned that the broadening of the bands is due primarily to how the wavefunctions change in shape as the result of interaction between a molecule and its environment – which largely consists of other molecules. Given the fact that those molecules which are disturbing the wavefunction for the molecule which is absorbing and re-emitting radiation are themselves interacting with other molecules and should therefore have their wavefunctions disturbed by those molecules, I would assume that there is always a finer level of detail where one would pick up additional spikes – except possibly once one hits the lifetime spreading due to the uncertainty principle as it applies to energy and time. Is this the case?

    Anyway, I will appreciate whatever response you might give me.

    Comment by Timothy Chase — 30 Jun 2007 @ 6:40 PM

  141. Dear Real Climate. “unprecendeted sunshine amounts in UK climate observations”

    This is my last blog on your site. I sent you observations, not a Theory or a Prediction, from the UK met office showing a upward and record trend in sunshine amounts for all regions of UK. The data and statistical analysis is of the highest quality and presented in a clear and concise fashion.

    I subjectively linked these to the rising temperature Trend in UK, which was probably an error, as although a common sense subjective view says they are linked I did not go on to prove it.

    However, this site is entitled “Real Climate” and I sent you real climate observations of an unprecedented nature, but you all seem so tied up in defending your CO2 position, that I really believe you are at risk of missing something important. It seems unlikely that such a definite Trend is a “localised effect”.

    Subjectively, April in UK was the most unusual April I have ever known in my 55years, with day after day of cloudless skies it got to be quite alarming being under the unforgiving sun day after day. When I checked through the Met office observational record I found this was part of a definite and sharp upward Trend.

    I thought I would share this with you, but will now leave you all to carry on.

    Comment by john — 30 Jun 2007 @ 6:45 PM

  142. Re #134: Ray, may I suggest again that the way to keep this sort of thing from becoming a problem is to have something like a weekly open thread a la John Quiggin (actually he does two, including a weekend one, but I’m not sure why he thinks both are needed). That way anything off-topic in a thread like this could be deleted out of hand and the value of the entire thread preserved for future readers. As it stands, I think the value goes away the moment the off-topic stuff starts in, and that’s unfortunate as there are often useful points made in the midst of the dross.

    Comment by Steve Bloom — 30 Jun 2007 @ 7:47 PM

  143. Re #142: Just to add, looking upthread about half of the coments in #s 9 through 20 were partly or wholly off-topic, which IMHO was already coming close to making the thread useless for someone trying to read through and extract useful information later. If there were a weekly open thread and a clear direction at the top of each thread for OT comments to be posted there instead, most of the problem would solve itself (perhaps to an extent that it would constitute a net decrease in work for the moderators).

    Comment by Steve Bloom — 30 Jun 2007 @ 8:18 PM

  144. re 130, Timothy, it sounds like you believe records from the IPCC should not be released because maybe some mean ole nasty skeptics might find something to debate with. Well, so much for open science!

    I do agree that what I would call working discussions/papers ought to be kept private. Otherwise the participants become inhibited and less effective. But semi-formal discourses or opinions ought to certainly be put out in public for scrutinity.

    Comment by Rod B — 30 Jun 2007 @ 10:50 PM

  145. Re #132: [But CO2 and temperature also show linear trends, Isn't that what we're concerned about?]

    It’s not just picking two variables, noticing that they are somewhat correlated, and postulating that a cause-effect relation exists. (And I’m still not sure how you decided which was cause, and which effect.) Instead, there’s an observation – CO2 is increasing due to human activity – and a prediction, backed up by a lot of theoretical & experimental work, that temperature will change as a consequence. So if we do see temperature increases that accord with predictions, that’s supporting data. See the difference?

    Comment by James — 1 Jul 2007 @ 12:48 AM

  146. Motl has run a simple scam. He compares the observed increase in global temperature to that predicted by Lindzen EXCLUDING feedbacks. He says we are 40% towards doubling CO2, but uses Lindzen’s sensitivity to doubling CO2 without feedbacks of 0.6 K with an increase in global temperature of 0.4 K, This puts the world 2/3 of the way and reaching doubled CO2 would only increase the global temperature by 0.2 K. OTOH, if we use the best estimate climate sensitivity of 3.0K and the observed 0.7 K increase in the last century we would be ~25% of the way. If we include the ~0.5 K of warming built into the system due to radiative imbalance we would be 40% of the way.

    Comment by Eli Rabett — 1 Jul 2007 @ 12:58 AM

  147. However, all you need is one major volcano to go off and all bets are off for some time on temperature increase.

    Comment by Edward H. Moran — 1 Jul 2007 @ 1:17 AM

  148. With environmental data, what constitutes a significant weak, medium, or strong coefficient of determination?

    Comment by Edward H. Moran — 1 Jul 2007 @ 1:25 AM

  149. Additionally, what method was used to determine:

    “CO2 is increasing due to human activity – and a prediction, backed up by a lot of theoretical & experimental work, that temperature will change as a consequence. So if we do see temperature increases that accord with predictions, that’s supporting data. See the difference?”

    Comment by Edward H. Moran — 1 Jul 2007 @ 3:10 AM

  150. [MODERATOR Gavin],

    I think I know where Rob B. came from, I hope your not assuming again that it came from me.

    Comment by Edward H. Moran — 1 Jul 2007 @ 3:20 AM

  151. All,
    Ed Moran’s co-author, Dr. Tindall has provided an email address in the curve-manipulation thread. I suggest we take further discussion of this work off line and provide comments directly to the authors.
    Hopefully, this will facilitate discussion in a civil manner and will serve to get discussions here back on track.

    Comment by ray ladbury — 1 Jul 2007 @ 6:06 AM

  152. Tim while each LINE broadens due to collisional interactions (pressure effect) the BAND narrows as temperature falls and higher rotational levels in the ground state are depopulated. These two effects mean that the lower you go in the atmosphere the larger the range of wavelengths/frequencies that can absorb.

    Densities at which you have to worry about the molecules that affect the molecules that affect the molecules are called liquids and the different layers are called solvation shells/nearest neighbors – next nearest neighbors, etc. For atmospheric effects you are pretty safely in the binary limit where one molecule only reacts with another at anytime. You can get some idea of this by calculating mean free paths.

    Comment by Eli Rabett — 1 Jul 2007 @ 9:12 AM

  153. Eli Rabett (#152) wrote:

    Densities at which you have to worry about the molecules that affect the molecules that affect the molecules are called liquids and the different layers are called solvation shells/nearest neighbors – next nearest neighbors, etc. For atmospheric effects you are pretty safely in the binary limit where one molecule only reacts with another at anytime. You can get some idea of this by calculating mean free paths.

    So what this would seem to suggest is that the fine-level detail becomes less pronounced and less complex at lower temperatures and at lower pressures. At the same time, it isn’t just noise, but structured such that you will arrive at the same plot each time under the same conditions – much like the electron scattering of a crystal.

    Anyway, my apologies for focusing on this aspect – it probably isn’t of that great an interest to others or perhaps of any interest at all. But it is something that I am curious about. I should really start trying to dig into the mathematics of it.

    In any case, what you focus on – the broadening of lines due to pressure and the broadening of bands due to temperature – is obviously more important. Moreover, the fact that you distinguish between the two suggests that the phenomena is in no way scale-free – and that answers one of my questions. But as far as a recursive extended neighborhood goes, this would see to be a pressure effect rather than a temperature effect, so I would assume that this won’t reveal itself in terms of the structure of the lines since lines are by definition without structure.

    Comment by Timothy Chase — 1 Jul 2007 @ 12:01 PM

  154. Eli and/or Ray,
    Perhaps you can help me with an area where my knowledge is a bit fuzzy. Once the greenhouse molecules absorb an IR photon, they can
    a)emit another photon (not necessarily of the same wavelength, since fluctuations may alter energy levels in the interim) at a random angle
    b)relax collisionally

    The greenhouse gas has to be in equilibrium with the radiation field in the spectral region where it is sensitive. However, to what extent does the energy absorbed become thermalized with the other nongreenhouse gases in the atmosphere. Based on the Maxwell distribution, ~4% of CO2 molecules will have sufficient energy to excite the same vibrational band as the IR photons. I guess my question is to what extent does the energy absorbed by the ghgs thermalize to other components of the atmosphere (e.g. N2, O2…), and what are the processes by which it does so?

    [Response: Here's the answer to the simpler part of your question. The GHG is in thermodynamic equilibrium with the other gases, including the non-GHG's like N2 and O2. The whole thing acts like a perfect gas in Earth conditions, and the equilibrium is maintained by collisions between molecules. Thus, there's only one temperature for the whole system: the same temperature for CO2, H2O, N2, O2, etc. You can think of a GHG molecule at a given place in the atmosphere either emitting a bit more energy than it absorbs (on average), leading to a radiative cooling which is made up for by tapping the kinetic energy of the other gases, or emitting a bit less energy than it absorbs (on average) leading to a radiative heating which spreads to the kinetic energy of the other gases. For blackbody radiation, the photon gas is also in thermodynamic equilibrium with the molecules, in the perfectly usual sense. For real gases, the way the thermodynamics of interaction with the photon gas works is more tricky. Maybe Eli can help me out with a simple explanation here, but one crude (but not too wrong) way to think of it is that Maxwell's equations are linear, Schroedinger's equations are linear, and the interaction between the electromagnetic field and the wavefunction of the molecule is linear; this means that in some sense, you can look at the thermodynamic equilibrium "one wavelength at a time," and then superpose to get the full solution. That's in any event the usual way Kirchoff's law is derived. Kirchoff did it "with mirrors," but Hilbert did it with integral equation kernels. Same physical assumption either way. (Now if you want to really bend your mind, think about what the existence of nonlinear optical devices -- like those frequency-doubling things used to make green laser pointers -- does to Kirchoff's law. It doesn't have anything to do with any known kind of atmosphere, but it's fun to think about) --raypierre]

    Comment by ray ladbury — 1 Jul 2007 @ 1:00 PM

  155. This article goes well with RealClimate – Water zapour: feedback or forcing?

    When surface temperatures change (whether from CO2 or solar forcing or volcanos etc.), you can therefore expect water vapour to adjust quickly to reflect that. To first approximation, the water vapour adjusts to maintain constant relative humidity. It’s important to point out that this is a result of the models, not a built-in assumption. Since approximately constant relative humidity implies an increase in specific humidity for an increase in air temperatures, the total amount of water vapour will increase adding to the greenhouse trapping of long-wave radiation. This is the famed ‘water vapour feedback’. A closer look reveals that for a warming (in the GISS model at least) relative humidity increases slightly in the tropics, and decreases at mid latitudes.

    That article also discusses how fast the water vapor responds to changes in forcings – within two weeks – while greenhouse forcings have lifetimes on the scale of years to centuries.

    Numerous reports agree with the prediction that temperatures will increase faster over land than over water. See Nature Runs Riot In Europe After Warm Winter, 2007

    The general reasons for this seem to be that water has greater heat capacity, and can mix surface heat down into the ocean, which isn’t possible over land, and that there tend to be more clouds around the marine boundary layer. These clouds still seem to be the largest source of uncertainty in estimating the climate sensitivity: Marine boundary layer clouds at the heart of tropical cloud feedback uncertainties in climate models, Bony&Dufresne GRL 2005

    Right now, continental land masses all over the planet are experiencing record droughts – and while we think of a drought as a temporary diversion from normal conditions, these may be permanent changes brought on by new global circulation patterns in the atmosphere and oceans, as well as by vegetation changes (i.e. deforestation and increased industrial agriculture).

    Radiative forcings change other variables like global circulation and water vapour feedback. Changes in global circulation and precipitation in turn have effects on the carbon cycle which seem to reduce the capacity of the system to absorb more CO2 – resulting in increased radiative forcings as more CO2 accumulates in the atmosphere.

    I think we will see a future world pummled regularly by heat waves, droughts, floods, and storms, in which agricultural capacity will be reduced and water will be increasingly scarce. Just how fast and how far will this go? The cryosphere response still seems very uncertain.

    Comment by Ike Solem — 1 Jul 2007 @ 1:29 PM

  156. Re #149: [Additionally, what method was used to determine...]

    That’s a pretty big question. You might start by reading some of the other threads on this site, popular books such as Weart’s “The Discovery of Global Warming”, or introductory texts on climatology, depending on your level of interest.

    But wait a minute. If you don’t already know how the “standard model” of AGW was developed, or the science that it’s grounded on, how can you possibly reject it on scientific grounds in favor of your hypothesis? It seems you must be relying on the egocentric approach: AGW would inconvenience me, therefore it can’t possibly be happening.

    Comment by James — 1 Jul 2007 @ 1:34 PM

  157. Rob B (#144) wrote:

    re 130, Timothy, it sounds like you believe records from the IPCC should not be released because maybe some mean ole nasty skeptics might find something to debate with. Well, so much for open science!

    I would expect you to know me a little better than that by now. I was explaining what I take to be their motivation, not mine.

    Anyway, this is the last point at which I will be responding on topics not relevant to this article on this thread. I suggest others do the same simply as a matter of courtesy.

    [Response: Thanks for the help in keeping things on-topic. So far, our moderation of these threads has been rather light and sporadic, largely because of lack of time. Thus, all of us here at RC rely on the readers to exercise some discipline and to keep the comments section from turning into a general climate chat-room. The cooperation is very much appreciated. --raypierre ]

    Comment by Timothy Chase — 1 Jul 2007 @ 1:41 PM

  158. The article says:
    “The molecule may radiate the energy back out again in a random direction.”

    Is this really a correct notion?
    Assuming that there’s a upward flux of energy and all radiated photons should obey Bose statistics, then why there’s no increased probability for emitting new photon in the same quantum state as the rest of them?

    Comment by Allan Kiik — 1 Jul 2007 @ 3:50 PM

  159. “As we have seen, in the higher layers where radiation starts to slip through easily, adding some greenhouse gas must warm the Earth regardless of how the absorption works. ”

    Now that is some GREAT science!

    Comment by Steve Case — 1 Jul 2007 @ 3:55 PM

  160. Re 158. I’ll take a stab. First, because there is no population inversion (i.e. there are still unexcited CO2 molecules, stimulated emission should be negligible. Second, the new photon is completely uncorrelated to the photon absorbed. It may have the same direction, spin, etc., but it need not. Indeed, as near as I can tell, it may not even have the same energy, as the energy levels of the molecule may be slightly different (due to collisions, etc.) at emission than at absorption. The important thing is, though, half the new photons will be heading back toward the surface, where formerly, virtually all the photons were outbound.

    Comment by ray ladbury — 1 Jul 2007 @ 4:00 PM

  161. re 157: “…their motivation, not mine…..”
    Fair enough.

    “…last point….responding on topics not relevant…”
    Fair enough.

    Comment by Rod B — 1 Jul 2007 @ 4:54 PM

  162. A long time ago (like in the 1970s) Mike Mumma and Co at Goddard observed a population inversion in CO2 high in the atmosphere of Mars (and I think Venus). This involves excitation of the 2349 cm-1 001 level (asymmetric stretch). Suffice it to say this does not happen in the Earth’s troposphere and as far as I know the same thing has not been observed anywhere in the Earth’s atmosphere

    Comment by Eli Rabett — 1 Jul 2007 @ 9:11 PM

  163. 153 Timothy, even isolated lines have (very narrow) structure, described by the natural line width. That structure is homogeneous (it is the same for each molecule).

    154 Ray it is possible to calculate the probability of collisional energy transfer from one quantum state to another using first principles. OTOH it is very complex and can only be done for simple cases. These calculations can be compared to pressure broadening or state to state energy transfer measurements. An example is the CO2-He system. Another is C2H2-He.

    Another approach is what are called power laws, scaling laws that calculate the collisional energy transfer probability in terms of the energy difference between states. These are linked back to simple models of the collision and have one or a few parameters which describe the average collision. This is one example and this is another.

    Hope that helps.

    Comment by Eli Rabett — 1 Jul 2007 @ 9:42 PM

  164. From “A Saturated Gassy Argument”

    What happens if we add more carbon dioxide? In the layers so high and thin that much of the heat radiation from lower down slips through, adding more greenhouse gas molecules means the layer will absorb more of the rays. So the place from which most of the heat energy finally leaves the Earth will shift to higher layers. Those are colder layers, so they do not radiate heat as well. The planet as a whole is now taking in more energy than it radiates (which is in fact our current situation). As the higher levels radiate some of the excess downwards, all the lower levels down to the surface warm up. The imbalance must continue until the high levels get hot enough to radiate as much energy back out as the planet is receiving.

    This particular paragraph seems somewhat problematic to me, particularly beginning with the sentence, “Those are colder layers, so they do not radiate heat as well.”

    Now by “heat” I would assume you are refering to the longwave radiation which is absorbed and re-emitted since gasses do not emit and blackbody radiation. But assuming this is the case, if they do not emit radiation that well, that also means that they let such radiation through quite well. But then what does it mean when you say “the high levels get hot enough to radiate…” This sounds like the oversimplified view that the greenhouse gases absorb and emit radiation at all frequencies – in essence – that they are black bodies. In this context, what does it mean for the higher levels to “heat up” enough to “radiate”?

    Once again, if they are not “radiating,” by which I would assume you mean “re-emitting,” then it would appear that they aren’t absorbing, but if they aren’t absorbing, then they are transparent to the radiation which they would otherwise absorb due to being opaque.

    Comment by Timothy Chase — 1 Jul 2007 @ 9:54 PM

  165. Two Views of Greenhouse Gases

    As a matter of fact, the first of these paints a picture of the higher levels of the atmosphere as having to warm up to the point at which they will radiate heat from below – which sounds like a “blackbody” view of greenhouse gases.

    So the place from which most of the heat energy finally leaves the Earth will shift to higher layers. Those are colder layers, so they do not radiate heat as well…. The imbalance must continue until the high levels get hot enough to radiate as much energy back out as the planet is receiving.

    In contrast, the following is much closer to how I understand how greenhouse gases work.

    As we have seen, in the higher layers where radiation starts to slip through easily, adding some greenhouse gas must warm the Earth regardless of how the absorption works. The changes in the H2O and CO2 absorption lines with pressure and temperature only shift the layers where the main action takes place.

    Additionally, I would assume that the increased pressure and temperature of the lower layers of the atmosphere will broaden both the lines and the bands so of the greenhouse gases in those layers so as to increase the absorption and re-emission at those levels. Thus while additional CO2 “throws another blanket on top,” it will also “make the lower blankets thicker,” as it were.

    Comment by Timothy Chase — 1 Jul 2007 @ 10:21 PM

  166. …since gases do not emit any blackbody radiation.

    I don’t think this is strictly accurate. For any part of the spectrum where absorptivity/emissivity is close to 1 (saturated?), the shape of the emission spectrum in that wavelength range will (I think) be the blackbody spectrum for that temperature. In the Archer Modtran calculator, if you set the altitude to zero, look up and vary the surface offset temperature (tropical atmosphere, other settings default) from 0 to 30 degrees (to increase the specific humidity) the IR emission spectrum looks more and more like a blackbody spectrum and is practically indistinguishable at an offset temperature of 30 degrees. Eli or anyone, comments?

    Comment by DeWitt Payne — 2 Jul 2007 @ 2:39 AM

  167. DeWitt Payne (#166) responding to (#164, #165) wrote:

    I don’t think this is strictly accurate. For any part of the spectrum where absorptivity/emissivity is close to 1 (saturated?), the shape of the emission spectrum in that wavelength range will (I think) be the blackbody spectrum for that temperature.

    If the gas is actually is saturated at groundlevel at that part of the spectra, then it is neither absorbing nor emitting – except at those times that a given molecule drops back to ground state and is capable of becoming excited again. As such, the absorbtion and emission must be taking place in the “wings” neighboring that part of the spectra which is saturated, that is, where satuaration has yet to occur, or at a higher altitude where the spectra is not saturated.

    Or so I would assume.

    Comment by Timothy Chase — 2 Jul 2007 @ 10:50 AM

  168. Misplaced System Inertia?

    Given my limited knowledge, and as I have already suggested, the problem lies with this passage:

    So the place from which most of the heat energy finally leaves the Earth will shift to higher layers. Those are colder layers, so they do not radiate heat as well. The planet as a whole is now taking in more energy than it radiates (which is in fact our current situation). As the higher levels radiate some of the excess downwards, all the lower levels down to the surface warm up. The imbalance must continue until the high levels get hot enough to radiate as much energy back out as the planet is receiving.

    It seems almost as if the author is trying to explain the inertia of the system, that is, why it takes a while for the system to re-establish a state of equilibrium.

    But it isn’t explained at this point. One of the obvious points at which the system has inertia would be the oceans, in fact, this would be the primary point. The oceans take a while to heat up. And they will even slow the rate at which the land heats up. This is the cause of the low pressures over land during the spring and summer which results in the upwelling of nutrients feeding algae blooms and resulting in hypoxia along the coastlines. (As a side point, this is what may have encouraged the growth of anaerobic sulfate-reducing bacteria during the major extinctions.)

    But there is another point as well: the atmosphere. It takes a while for the atmosphere to heat up – which would also affect the spreading of the bands as explained by Eli Rabett in #152. The reason for this lies in the fact that it will take a while for the heat to become thoroughly mixed – and will also in part depend upon the inertia of the oceans.

    Comment by Timothy Chase — 2 Jul 2007 @ 11:16 AM

  169. If the gas is actually is saturated at groundlevel at that part of the spectra, then it is neither absorbing nor emitting – except at those times that a given molecule drops back to ground state and is capable of becoming excited again.

    There seems to be some confusion over the meaning of saturation. You are describing a population inversion, I think. In that case, absorption no longer follows the Beer-Lambert (IIRC) law and the ratio of transmitted light intensity to incident light intensity gets larger as the incident intensity increases. I don’t believe that a population inversion for CO2 or H2O can exist in the earth’s atmosphere at current temperatures. Otherwise you could build a CO2 laser in the open with no need for pumping. What I meant by saturation is the ratio of transmitted intensity to incident intensity in the wavelength region of interest is about 0.001 or smaller and is not a function of incident intensity.

    Comment by DeWitt Payne — 2 Jul 2007 @ 11:17 AM

  170. DeWitt Payne (#169) wrote:

    I don’t believe that a population inversion for CO2 or H2O can exist in the earth’s atmosphere at current temperatures. Otherwise you could build a CO2 laser in the open with no need for pumping.

    This quite possible.

    I remember that Ray Ladbury had raised the question of whether I was equating saturation with population inversion a while back, although he wasn’t sure whether the two were different or not – from what I could tell. In fact, I suspect you are right: saturation wouldn’t be simply a function of whether all the molecules have reached an excited state, but whether they are sufficiently dense that over a relatively short distance all light at the peak frequency will be absorbed. More pieces to the puzzle, I suppose.

    At the same time, I don’t quite see how gases could become blackbodies even within a given range of wavelengths. But it wouldn’t really resolve the problem of “atmospheric inertia” from what I can see since it is unlikely that the bands at which carbon dioxide reaches saturation would be unlikely to be where the temperature has risen to, at least within the upper atmosphere.

    Additionally, that which is absorbed must be re-emitted, although it may be re-emitted in any direction, but that which is not absorbed will get through. Or at least this is how I understand it. Unless of course some of the energy is lost due to kinetic interactions, warming the atmosphere. But this latter point was raised by Raymond Pierrehumbert pointed out while stressing that it was fairly minor.

    In any case, I am not actually arguing with either author, but simply pointing out what is opaque to me – which is I believe part of the reason why they post these essays in the first place. Moreover, even if someone does not consciously notice that a given part of the explanation is unclear, at a subconscious level, they will notice, and as in literature, this will make the narrative that much less psychologically powerful, reducing the degree to which they are convinced.

    Or at least this is my understanding of human psychology.

    Comment by Timothy Chase — 2 Jul 2007 @ 12:04 PM

  171. Regarding #164, #165, #167, #168, #170

    At this point I will limit myself to the issues I have raised so far. I suspect that I may have already shared more than enough of my confusion.

    No need to address everything I have raised, but whatever light one might throw on these issues will be appreciated.

    Comment by Timothy Chase — 2 Jul 2007 @ 12:23 PM

  172. Timothy, Saturation simply means that all the radiation that is in the sensitive band is getting absorbed, so if you add more gas, the only radiation it can absorbe is the rediation in the wings of the spectral line.
    WRT black body radiation, keep in mind that this is an abstraction–there are not true black bodies. Instead, the emissivity of a real gas becomes a function of wavelength. Thus, over the vibrational line, CO2 has an emissivity which varies from small in the wings to effectively one in the middle if I’m interpreting things correctly. So in the range where the emissivity is nonzero, it does indeed behave like a black (or gray) body. Keep in mind that the UV radiation that does escape is almost all coming from the upper atmosphere, so the region it is coming from really is that cold. Remember Eli’s comment about how the radiation from Venus makes it look as if it were cooler than Earth–it’s just because so little radiation escapes if I understand correctly.

    Comment by Ray Ladbury — 2 Jul 2007 @ 1:12 PM

  173. At the same time, I don’t quite see how gases could become blackbodies even within a given range of wavelengths.

    It’s my understanding that anything that isn’t perfectly transparent or perfectly reflective, i.e. an emissivity/absorptivity greater than zero, is a blackbody. When the emissivity is less than one, the emission spectrum will show fine structure as the emissivity of each line varies with wavelength.

    Comment by DeWitt Payne — 2 Jul 2007 @ 1:47 PM

  174. Re Ray Ladbury (#172)

    I greatly appreciate the response…

    I am going to have to chew on it a little, so I might not be able to respond until later today. But in any case this is obviously an area I am still trying to get a handle on, and I suppose reaching the point at which I am confused and aware of my confusion is itself a form of progress.

    Comment by Timothy Chase — 2 Jul 2007 @ 2:11 PM

  175. Hm. Ray says there are no true blackbodies, it’s a theoretical abstraction.
    DeWitt says he understands everything except theoretically perfect zero emitter/absorbers are black bodies.
    Cites, please, folks? ‘Sez whom’ so we can look at sources?

    Comment by Hank Roberts — 2 Jul 2007 @ 2:33 PM

  176. Ray Ladbury (#172) wrote:

    Timothy, Saturation simply means that all the radiation that is in the sensitive band is getting absorbed, so if you add more gas, the only radiation it can absorbe is the rediation in the wings of the spectral line.

    This is my understanding as well. (Last paragraph of #165.)

    I assume that this is still a function of column height, however, such that it follows a simple exponential decay law of the form 1-e^(-kh) where k is a constant and h is the height of the column.

    WRT black body radiation, keep in mind that this is an abstraction–there are not true black bodies. Instead, the emissivity of a real gas becomes a function of wavelength. Thus, over the vibrational line, CO2 has an emissivity which varies from small in the wings to effectively one in the middle if I’m interpreting things correctly. So in the range where the emissivity is nonzero, it does indeed behave like a black (or gray) body.

    Part of the problem which I was having with this point (second paragraph of #170) lay in my assumption that the temperature of the outermost layer of the atmosphere falls off to effectively zero, at least in comparison to the spectra of carbon dioxide. However, you raise a point in the following pertaining to the “effective temperature” of the earth which I hadn’t thought of in connection with this.

    Keep in mind that the UV radiation that does escape is almost all coming from the upper atmosphere, so the region it is coming from really is that cold. Remember Eli’s comment about how the radiation from Venus makes it look as if it were cooler than Earth–it’s just because so little radiation escapes if I understand correctly.

    This is the mention of the effective temperature of Venus which is cooler (I would assume) than the surface of the earth. (I make this assumption because the thermal radiation going in at the outer mmost layer of the atmosphere must be balanced by the thermal radiation going out in both the case of Venus and the Earth, and I would assume that the outermost layer of the Earth’s atmosphere receives less radiation – unless this has something to do with the scattering of light at the outer layer of Venus’ atmosphere.)

    In any case, the upper atmosphere will warm, and the degree to which it warms should be sufficient for it to emit grey body radiation within some parts of the spectrum where carbon dioxide is opaque to radiation. Additionally, lower parts of the atmosphere should warm still more so as to emit thermal radiation at shorter wavelengths where carbon dioxide is opaque as well.

    One final note: if the above analysis is correct, then a layer will have to be a certain depth (or width) for it to become fully opaque at a given temperature. But at this point the mathematical analysis will become complex enough that it will be more difficult to put into words, particularly as the temperature varies with altitude.

    DeWitt Payne (#173) wrote:

    It’s my understanding that anything that isn’t perfectly transparent or perfectly reflective, i.e. an emissivity/absorptivity greater than zero, is a blackbody. When the emissivity is less than one, the emission spectrum will show fine structure as the emissivity of each line varies with wavelength.

    Understood and most certainly appreciated – particularly the finer details. All of this helps flesh things out considerably.

    Comment by Timothy Chase — 2 Jul 2007 @ 3:36 PM

  177. Correction to #176

    I had written:

    This is the mention of the effective temperature of Venus which is cooler (I would assume) than the surface of the earth. (I make this assumption because the thermal radiation going in at the outer mmost layer of the atmosphere must be balanced by the thermal radiation going out in both the case of Venus and the Earth, and I would assume that the outermost layer of the Earth’s atmosphere receives less radiation – unless this has something to do with the scattering of light at the outer layer of Venus’ atmosphere.)

    The scattering matters.

    The effective temperature will be a function of the amount of radiation reaching the surface and being absorbed so that it becomes thermal radiation. Since so much light is scattered by the upper clouds of Venus (sulfuric acid, if I remember correctly) much less light will reach the surface. This lowers the effective temperature of Venus in all likelihood below that not only of the Earth’s surface, but below the effective temperature of the earth since the Earth scatters much less light before it reaches the surface and is absorbed so that it becomes thermal energy.

    See:

    http://www.atmos.washington.edu/2002Q4/211/notes_greenhouse.html

    Comment by Timothy Chase — 2 Jul 2007 @ 4:04 PM

  178. A Couple More Notes

    1. The last sentence of the last paragraph of #168 was poorly phrased on my part:

    But there is another point as well: the atmosphere. It takes a while for the atmosphere to heat up – which would also affect the spreading of the bands as explained by Eli Rabett in #152. The reason for this lies in the fact that it will take a while for the heat to become thoroughly mixed – and will also in part depend upon the inertia of the oceans.

    The bit stating, “… it will take a while for the heat to become thoroughly mixed” if taken literally would suggest that the atmosphere reaches a uniform temperature throughout – which is obviously false. What it reaches is a state of quasi-equilibrium where the temperature will remain roughly constant at any given altitude.

    2. For the purpose of mental imagery, I think of the opaqueness of the atmosphere as being similar to that of a fog such that it becomes more opaque the further an object is from the “observer.” Of course, if it is emitting radiation within that part of the spectra it is opaque to, this would make it a glowing fog. I suppose that might be a nice visual effect for a science fiction story.

    Comment by Timothy Chase — 2 Jul 2007 @ 5:38 PM

  179. Is not the physical process of black/graybody ala Planck radiation (primarily molecular/ionic acceleration/deceleration??) totally separate from the process of emission/absorption that goes on between the earth’s (blackbody) infrared radiation and gas molecules (molecular bond rotation and translation and electronic energy levels??)? Or did I snooze through part of this discussion??

    [Response: I think maybe you're confusing Planck radiation and Cerenkov radiation. It's true that electromagnetic radiation and absorption (classically called "radiation reaction") involved accelerations of charged bodies. However, it's the motion of the charge distribution associated with molecular vibrations and rotations that results in the absorption and emission of infrared we're talking about in connection with the atmosphere. It's not acceleration and deceleration of ions or molecules as a whole that are involved. The Planck function describes the statistical properties of large numbers of molecular absorption and emission events of the former type, in a substance whose molecules are in thermal equilibrium at a given temeprature T. --raypierre]

    Comment by Rod B — 2 Jul 2007 @ 10:08 PM

  180. [[It's my understanding that anything that isn't perfectly transparent or perfectly reflective, i.e. an emissivity/absorptivity greater than zero, is a blackbody.]]

    No. A blackbody has an emissivity/absorptivity of 1. A body with 0 < e < 1 is a graybody. A body with e varying with wavelength is a realistic body.

    Comment by Barton Paul Levenson — 3 Jul 2007 @ 7:36 AM

  181. I stand corrected. What I meant was that any thing with non-zero emissivity/absorptivity at the appropriate wavelengths will emit thermal radiation rather than is a blackbody. I think this was implied in the rest of my comment though:

    When the emissivity is less than one, the emission spectrum will show fine structure as the emissivity of each line varies with wavelength.

    But my statement as written was indeed technically incorrect as a true blackbody must have an emissivity identical to one and there is no such animal.

    Comment by DeWitt Payne — 3 Jul 2007 @ 3:02 PM

  182. As long as we’re being trying to make technically correct statements:

    Ray Ladbury stated in comment #172:

    Saturation simply means that all the radiation that is in the sensitive band is getting absorbed…

    It isn’t all getting absorbed, that would imply an absorptivity identical to one or a true blackbody. The amount that gets through may be vanishingly small, but it’s not zero. So it’s nearly all, not all.

    Comment by DeWitt Payne — 3 Jul 2007 @ 3:31 PM

  183. Can someone point to an explanation of how any molecule can bump into a GHG molecule so the GHG gas’s bonds get to vibrating and sometimes they will get rid of that energy when they emit a photon?

    I realize that ‘bonds’ and ‘vibrating’ are imprecise words for whatever’s going on there, and that there’s not really a ‘there there’ —- and any nonmathematical explanation of the physics has to be closer to poetry.

    Eli’s written about this enough for me to realize I don’t have words that explain how “sunlight heats Earth, Earth warms atmosphere, eventually photons depart into space, and GHG emitted will continue to change how that happens for a few centuries til an equilibrium is reached.”

    Comment by Hank Roberts — 3 Jul 2007 @ 3:33 PM

  184. raypierre (inline to #179) wrote:

    I think maybe you’re confusing Planck radiation and Cerenkov radiation. It’s true that electromagnetic radiation and absorption (classically called “radiation reaction”) involved accelerations of charged bodies. However, it’s the motion of the charge distribution associated with molecular vibrations and rotations that results in the absorption and emission of infrared we’re talking about in connection with the atmosphere.

    I thought that “Cerenkov radiation” refered to the radiation emitted by a charge traveling faster than the speed of light within a medium, a bit like the sonic boom of something traveling faster than speed of sound. The radiation is a blue-green light, if I remember correctly. But I understand accelerating charges will typically emit radiation, too, although I remember there being some controversy over second and third derivatives involving Feynman (who argued for the third) and the principle of general relativity – for example, a charge being suspended in a gravity well won’t emit radiation. I don’t know what the current status of that one is, but it would be a little odd if they haven’t figured it out as of yet.

    Then again, acceleration and gravity aren’t fully equivilent even locally (as Mach would have prefered and as Einstein originally intended) since the following will contain non-zero elements in any coordinate system if and only if space is curved:

    {R^\rho}_{\sigma\mu\nu} = \partial_\mu\Gamma^\rho_{\nu\sigma}     - \partial_\nu\Gamma^\rho_{\mu\sigma}     + \Gamma^\rho_{\mu\lambda}\Gamma^\lambda_{\nu\sigma}     - \Gamma^\rho_{\nu\lambda}\Gamma^\lambda_{\mu\sigma}

    Comment by Timothy Chase — 3 Jul 2007 @ 4:10 PM

  185. Yes, Cerenkov radiation is probably not what Ray meant. The radiation from the acceleration/deceleration of charged particles is a much more general phenomenon, subsets of which include bremstrahlung, cyclotron and synchrotron radiation.

    Comment by SCM — 3 Jul 2007 @ 9:21 PM

  186. Way, way off topic, but funny: In the early days of nuclear physics, the way they used to find the beam from an accelerator was to move their head around until they saw the blue flash of Cerenkov radiation!

    I think the way to understand blackbody radiation is to remember that the closest we actually come to it is the radiation emitted from a hole in a cavity. The radiation is emitted by the walls of the cavity, but it interacts not just with the walls of the material, but also with the radiation field itself and comes to equilibrium before it leaves the cavity. The Universe itself can be viewed as such a cavity–at a temperature of 3 Kelvins.

    Comment by ray ladbury — 3 Jul 2007 @ 9:44 PM

  187. re raypierre’s response to 179: I don’t think I was confusing Cerenkov radiation. Actually I’m not smart enough to do that.:-) Let me see if I’m getting it. The earth radiates ala Planck black/graybody radiation in the infrared region as determined by the acceleration of molecular-sized charges caused by the collisions and course reversals which is based on the mv^2 energy — = temperature. But the absorption (and subsequent emission) by gas molecules is not Planck based. Rather the E-M energy is absorbed by certain gasses and stored in the intramolecular bonds by virtue of the bonds bending or stretching back and forth, or by electrons rising to a higher coincident energy levels. Now this latter process does not affect the temperature of the molecule, i.e. the molecule as a whole does not go any faster ala mv^2, nor does any of its neighbors, and the temperature of this slice of the atmosphere says the same. Then this molecule can “relax”, give up its bonding energy in the form of emitted E-M radiation at pretty much the same frequency that was initially absorbed. OR, before it re-emits, the molecule can crash into another and transfers some of its bond energy to kinetic energy in the collidee, raising its temperature. I suppose collidee can now become a collider, maybe even to the original molecule and transfer some of its kinetic energy to the original, but as kinetic energy not as bond replacement energy (or that, too????)

    Is this accurate? Close? Thanks.

    Comment by Rod B — 3 Jul 2007 @ 9:45 PM

  188. Hank Roberts wrote in #183

    Can someone point to an explanation of how any molecule can bump into a GHG molecule so the GHG gas’s bonds get to vibrating and sometimes they will get rid of that energy when they emit a photon?

    I’ll take a stab. You have two types of collisions, elastic and inelastic. In elastic collisions, no kinetic energy is lost by conversion to a different form like heat. Think pool balls or those rows of suspended ball bearings. In an inelastic collision some of the kinetic energy is converted to other forms of energy. Think car crashing into tree, things bend and stay bent. When molecules collide inelastically, the kinetic energy lost can excite internal modes in one or both of the molecules which then may return to their ground states by emitting photons. See here for a basic definition of elastic and inelastic collisions or google for more references. I wouldn’t begin to attempt a more detailed explanation of molecular collision theory here, even if I could.

    Comment by DeWitt Payne — 3 Jul 2007 @ 11:09 PM

  189. SCM (#185) wrote:

    The radiation from the acceleration/deceleration of charged particles is a much more general phenomenon, subsets of which include bremstrahlung, cyclotron and synchrotron radiation.

    I will have to ask you to explain the difference between those some time. As for the above, the farthest I ever got was being able to step through the derivation of Schwartzchild’s solution. Pretty stuff.

    Comment by Timothy Chase — 3 Jul 2007 @ 11:13 PM

  190. I recently posted a piece entitled “What Enhanced Greenhouse Gas Effect?” on the PhysOrg and the Environment Site forums, and a few days later Real Climate had an article called “A Saturated Gassy Argument”, which seemed to be an answer to my posts, although on a different site. Anyone who reads my posts will see that I am sceptical, at present, about the enhanced GHG effect. However, I am ready to be convinced otherwise by a properly reasoned physics explanation, which would require sufficient maths to be successful.

    The “Saturated Gassy Argument” gave an interesting historical account of the GHG effect, and made an attempt at explaining how enhancement can occur at high altitudes, in spite of the fact that 100% absorption of power by CO2 at certain wavelengths occurs at lower levels. This argument was unconvincing because no numbers were given. It was left to the reader to establish for himself/herself whether the increased amount of absorption would be significant in view of the claimed high altitudes, and low densities involved. (And any other considerations like absorption cross section.) I want to have a go at this, but it will take time, and if anyone can post relevant information it would be greatly appreciated.

    Part 2 of this RC post was called “What Angstrom didn’t know”, and did, indeed, try to give a little more by way of numbers, but I still found it to be confusing. In particular, the term “absorption factor”, was said to be the rate of decay of the exponential curve for absorption of infrared energy by increasing numbers of CO2 molecules. The appropriate curve for the atmosphere could, presumably, have been given, and the point on the curve for the present day could have been shown. This should have been done, because the numbers of CO2 molecules involved, and not the concentration per se, is what is relevant.

    Again, the last paragraph on page 1 of Part 2 mentions the product of the absorption factor and the amount of CO2, but no explanation is given of how these parameters are handled. No units are given.

    On the second page of this piece, a figure is shown for Absorption Factor (still unclear) against wavelength. This was said to be based on the Hitran data. I have not seen anything like this in the Hitran data, but it is obviously of great importance, and I should be very grateful if someone would please be kind enough to give me a web reference to this item. One astonishing thing about it is the vast dynamic range shown, from 10^5 down to 10^-5, a range of 10^10. These results were, presumably not measured. Indeed, the text mentions that the absorption results were computed for typical laboratory conditions, whereas what really matters is what is happening in the real atmosphere. What was the number of CO2 molecules in the calculation? Please can we have some numerical, physics explanation?

    Aubrey E Banner
    Cheshire, UK.

    Comment by AEBanner — 4 Jul 2007 @ 12:00 PM

  191. [[On the second page of this piece, a figure is shown for Absorption Factor (still unclear) against wavelength. This was said to be based on the Hitran data. I have not seen anything like this in the Hitran data, but it is obviously of great importance, and I should be very grateful if someone would please be kind enough to give me a web reference to this item. One astonishing thing about it is the vast dynamic range shown, from 10^5 down to 10^-5, a range of 10^10. These results were, presumably not measured. Indeed, the text mentions that the absorption results were computed for typical laboratory conditions, whereas what really matters is what is happening in the real atmosphere. What was the number of CO2 molecules in the calculation? Please can we have some numerical, physics explanation?]]

    The absorptivities are calculated nowadays because we know what causes them; absorption lines are a quantum effect and can be predicted with extreme precision. That’s what HITRAN (and HITEMP) are all about. The number of molecules involved is one for any given isotope. That’s all you need.

    Are you suggesting that there’s a discrepancy between the computed values and the observed values? What’s your source for the latter?

    As for variation in the atmosphere, that’s been known for a long time from empirical data going back to the 1940s. In brief, the optical thickness of a given mass of gas in most circumstances varies directly with the ambient pressure and inversely with the square root of the temperature. The raw optical thickness is the product of the absorption coefficient and the specific mass (mass per unit area) present, or if you like, the absorption coefficient times the density times the path length, which gives the same answer.

    Comment by Barton Paul Levenson — 4 Jul 2007 @ 5:11 PM

  192. I’ve been playing with the Archer Modtran calculator. It looks like increased water vapor actually enhances the effect of CO2, at least in a radiation only model. If you compare a high specific humidity case like the tropical atmosphere with a low surface temperature and corresponding low specific humidity case like subarctic winter, the sensitivity factor to doubling CO2 is more than twice as high for the tropical atmosphere than for the subarctic winter with both at constant relative humidity. This seems counter-intuitive until you look at the spectra and see what’s actually happening.

    Comment by DeWitt Payne — 4 Jul 2007 @ 8:52 PM

  193. Thank you for your comments, #191, #192, but I am still not sure about the “Absorption Factor”. Is it the same as the absorption cross section, as in the HITRAN data? Again, is “absorptivity” the same thing?

    No, I am not suggesting any discrepancy between computed and observed values. I just want the facts.

    What I should really like to see is a physics analysis of the enhanced GHG effect, line by line, equation by equation, and diagram by diagram. Surely somebody can post this, or at least post a reference to the work, preferably a web reference?

    Aubrey E Banner
    Cheshire, UK.

    Comment by AEBanner — 5 Jul 2007 @ 11:40 AM

  194. Aubrey, it would depend greatly on what you already understand, and how much physics and math you’ve studied. Is it safe to assume you understand quantum mechanics and the work from the high altitude gas studies mentioned in the AIP History (first link under ‘Science’)? The cites there likely have much of what you want to know. This is a huge field widely distributed in the literature, not somethihng that can be put on a website in full mathematical detail.

    In the AIP History, after reading the section on radiation physics, have you already responded there to the author’s request for people to comment on how they understood the presentation?

    Mathematical physics without the math is poetry, at best.

    Possibly you’re fully competent in radiation physics already, I dunno — I’m just a reader here. But it sounds like you’re asking for the Moon to be put on a plate so you can look at it close up, to me. Won’t fit.

    Comment by Hank Roberts — 5 Jul 2007 @ 12:10 PM

  195. #193 Aubrey,

    As free resources you might want to have a look at Ray Pierrehumbert’s, work in progress which is available online (but only complete up to about Chapter 5):
    http://geosci.uchicago.edu/~rtp1/ClimateBook/ClimateBook.html
    The IPCC report AR4 is also available online, emphasis is more a thorough review of recent literature:
    http://ipcc-wg1.ucar.edu/wg1/wg1-report.html

    If you want to read the original papers on which it is based then Google Scholar is always worth a go:
    http://scholar.google.com/

    Personally, I’ve just ordered “The Physics of Atmospheres” by John T. Houghton which is an undergraduate text in the area. It’s a sufficiently large area that I don’t think any online resource is really suitable.

    …and definitions for absorption coefficients are always fun…

    Comment by SomeBeans — 5 Jul 2007 @ 12:18 PM

  196. “Erik” (12:23pm) is blogspam, please add to filters.

    Aubrey, I looked at PhysOrg; nobody answered you because your posting there made clear you haven’t read the basic science,and can benefit from the threads posted here. I’m sure they weren’t posted as answers to you personally — but they may help.

    At PhysOrg, you are stating your firm beliefs about what can possibly be true, and saying human activity can’t add to the natural greenhouse. Therre’s a lot to learn.

    UCAR has a nice page, here:
    http://www.ucar.edu/learn/1_3_1.htm

    including this animation:
    http://www.ucar.edu/learn/images/carbon.gif

    Comment by Hank Roberts — 5 Jul 2007 @ 12:41 PM

  197. I audited an undergrad physics course on “Radiation in planetary atmospheres” last term; the class notes are still online at http://www.atmosp.physics.utoronto.ca/people/strong/phy315/phy315.html
    Lecture 18 is where the greenhouse effect comes in explicitly, but some of the earliest lectures spell out the underlying basic laws and the math involved: Beer’s Law, Schwartzchild and such; lots of PDEs. The prof derived a lot of the equations on the board but I think the class notes are more summary form. I’m afraid I can’t reproduce the derivations as I was just auditing. The homework for the real students stressed the math. Prof. Strong has contributed to the vast spectroscopy databases from lab measurements, but also taken field observations both via satellite and balloon sondes (including the infamous runaway balloon that RCAF couldn’t bring down) :-) The sonde data provides direct measurement of CO2 profiles by height; these are covered in the course notes.

    I would definitely recommend Ray Pierrehumbert’s online book draft, cited above, as a good source for in-depth discussion of how all this fits together. His prose is quite readable yet you’ll also find the equations there.

    Comment by Jim Prall — 5 Jul 2007 @ 1:12 PM

  198. Re: Comment 6: Response “The reason the stratosphere cools upon increase of CO2 is that the balance in the stratosphere is between absorption of solar radiation by ozone and cooling by infrared emission. As you increase the CO2, there is excessive radiative cooling, so the stratosphere has to cool down to come back into balance.”

    Not sure I understand the mechanism as to why the stratosphere cools.

    For a simple case, no CO2, the specific radiation frequency that stratosphere CO2 could block, passes through the stratosphere, unaffected. Adding CO2, causes a specific portion of the up coming radiation to be blocked which would seem to me to increase the temperature of the stratosphere.

    The stratosphere CO2 after absorption of the up coming specific radiation frequency, would (statistically, if it strikes another molecule before re-emission) either transfer some energy to another stratosphere gas molecule (might not be CO2) as well as reemit, as you have stated, statistically up and down. As an number of the CO2 molecules will transfer energy to other stratosphere molecules, the stratosphere temperature should increase, as compared to the no CO2 case.

    The other possible explanation for the decreasing stratosphere temperatures would be a reduction in low level clouds. A reduction in low level clouds would reduce the amount of up coming radiation (short) that ozone can absorb which would cool the stratosphere. If this mechanism is correct, I would expect the stratosphere would start to warm, as due to solar changes, it is my expectation that low level clouds will increase.

    Comment by William Astley — 5 Jul 2007 @ 2:15 PM

  199. Mr. Astley, you’re reaching your conclusions by reasoning from your beliefs without checking them.

    You can look this stuff up.

    Try the first half dozen of these articles.

    Does anything you read here change something that you believed to be true?:
    http://scholar.google.com/scholar?q=cooling+stratosphere&hl=en&lr=&scoring=r&as_ylo=2002

    Comment by Hank Roberts — 5 Jul 2007 @ 2:36 PM

  200. “Try the first half dozen of these articles. Does anything you read here change something that you believed to be true?”

    No.

    As I said I have not seen an explanation of the mechanism, as how additional CO2 causes the stratosphere to cool. (See my comment 198). The links you provide are a shot gun of papers related to the stratosphere, none of which answers my question. A brief survey of the papers indicates that there are other concurrent changes that can explain a portion of stratosphere cooling such as a reduction in ozone.

    I bring up the change in low level clouds as I believe, the 20th century changes in low level clouds has not been taken into account in the analysis.

    Comment by William Astley — 6 Jul 2007 @ 12:51 AM

  201. For anyone interested, I have some summaries of basic climate concepts on my climatology page:

    http://members.aol.com/bpl1960/Climatology.html

    Recently I’ve been adding rebuttals of denialists. So far I’ve got John Dodds and Viscount Monckton. I’m thinking of doing Rush Limbaugh, although it would take a really long web page just to list all his deliberate lies about the subject (e.g. “one volcano puts more pollution in the air than all human emissions since the Industrial Revolution began”).

    Comment by Barton Paul Levenson — 6 Jul 2007 @ 7:28 AM

  202. I’ve just begun to review the science of greenhouse warming. I’ve already gathered that GCM’s have a real issue with how they handle the effects of clouds for a number of reasons. But let me try to phrase a question in the spirit of the post of gas saturation and single layer models. The first part of my question seems straightforward to me. That is, given that lower levels of the atmosphere the main greenhouse gas is water vapor it would seem that most of the cooling takes place through dry portions of the troposphere. Then the question is what will warming do to the wet/dry tropospheric distribution, as supposed to overall increase in water vapor due to the increased temperature. Is this taken into account in GCM’s? If so, how? Somewhat in the same vein, I’ve heard Tapio Schneider argue that global warming would likely make tropical regions more humid and extratropical latitudes drier (in an average sense), while increasing the overall water vapor content.

    Comment by Ignacio Mosqueira — 8 Jul 2007 @ 7:29 PM

  203. RE #96 & 86, I couldn’t respond sooner, since I was off-line for a long time.

    I specificially chose the word “denialist” in my entry. I consider anthropogenic global warming “skeptics,” “contrarians,” and “denialists” to be somewhat different from each other. These are the meanings I give:

    SKEPTIC: a person who has some doubts based on some good evidence or theory, or bec of a lack of good evidence or theory. This kind of person does not have any agenda, except they seek scientific validity (which usually requires high confidence, such as 95%). I do not believe there are a whole lot of climate scientist skeptics left; most have come to believe AGW is real, though they might debate the details of it. Skeptics are needed to keep science honest.

    CONTRARIAN: a person who just likes to be contrary. It’s in our Western culture, our rugged individualist ethos, and in some people’s personality make-up. Perhaps Crichton could be considered one. Maybe society needs a few of these, as a gene pool could use diversity and some mutations, but they could also be counterproductive and harmful, as when a problem is real and dangerous, and they convince others to do nothing about it.

    DENIALIST: a person who has some agenda re AGW and its policy implications. They might be tied into fossil fuels, or they might fear economic harm or totalitarianism if we address AGW, or the loss of their world view. I think these people might actually believe or suspect AGW is real, but fear they or society has something great to lose if they do admit to it and to addressing it. These types will probably never change their mind, no matter how much evidence comes in.

    It’s the denialists and contrarians (not the skeptics) who might make contradictory arguments against AGW. And it is ususally people who are not in the spotlight, but people you meet at parties or on blogs, who have heard arguments against AGW from various sources, and are simply relaying them, without concern about inconsistences….sort of like a shotgun approach, with the idea that at least one bullet will knock out the feared thing…but for a discerning person, such an approach lacks credibility.

    So, PHE, you seem to be a skeptic and not a denalist.

    Comment by Lynn Vincentnathan — 9 Jul 2007 @ 3:03 PM

  204. Mr. Astley, have you read this?
    http://www.realclimate.org/index.php/archives/2006/11/the-sky-is-falling/

    Comment by Hank Roberts — 9 Jul 2007 @ 3:49 PM

  205. I just wanted to point at the slowly-emerging fact that getting the right answers at last requires a highly interdisciplinary approach that has not yet quite evolved… as a pertinent example of what I mean, consider that many phytoplankton, which hav been on the earth as a species for vastly more time than mankind, have evolved both methods of cloud control and the means to elevate themselves into the atmosphere where they live [AND SO ALTER GAS BALANCES] and have UV protection [AFFECTING both UV and heat] whilst dispersing themselves over vast distances throughout the atmosphere…

    These ‘clever’ little creatures kept the earth in favourable balance of temperature way different than what it would have been by Physics alone , something which made it possible for mankind to eventually appear and begin killing them off in enormous numbers by acidifying the sea with XS CO2 as we now see today …

    Phytoplankton manufacture and release Dimethyl Sulphide when under stress of iron deficiency , a gas which rises through the atmosphere to form potent sulphate aerosols and create clouds [thus provoking storms by means of the instability of the atmosphere and providing themselves with the means to spread to other areas of sea where there may be more iron]

    The implication then , due to the massive contribution of the sea to the atmosphere and the vast numbers of phytoplankton and their ability to populate any ammount of ocean in but three days given travces of iron, is that one cannot ignore the biological DYNAMICS … one needs to consider the input of iron to the ocean surface in CO2 modelling ! … the main sources are from dust blown from the land [wind and drought dependent] , overflow of water from acidic soils and peat bogs [dependent on heavy rainfall to wash out iron chelates of humic acids and fulmic acid] , from heavy storms stirring deep waters to the surface, and from changes in ocean currents causing upturn at suitable coastlines and ocean ridges/mountains/volcanoes …

    The models will thus fail in necessary extreme accuracy [since there are many instabilities through positive feedback effects] without taking into account all disciplines in science , notably the massive [and pre-historical] biological offsetting effects and indeed the disastrous positive feedback in CO2 release AND less absorption by the oceans as we continue our already insane killing of the base of the food webs in the oceans with simply too much CO2 …

    It seems then that we sit o a much-unrecognised knife-edge between a world that could be a paradise and one which more resmbles the common misunderstanding about ‘hell’

    Ironically, work in the last 15 years has revealed that the oceans are largely dead simply because of lack of only trace elements [typically iron] required in the tiniest ammounts only to turn dead oceans into thriving eco-systems which could absorb a vast ammount of CO2 back into biomass [where it came from!] rather rapidly [and so perhaps save our skins from our short-sighted 'convenience' living which will apparently shortly prove most inconvenient in extreme]…

    The irony is that we are already killing off perhaps the only, and certainly the cheapest and safest, method of restoring the balance which we have upset by our extremely short-sighted methods of industrialisation , faulty methods of assessing value in ‘economics’, and consequently rather inadequate governance and leadership …

    The sea could save us only if we stop almost immediately from killing it off and introduce international co-operation in place of competition [since the sea is international and 'farming' the sea would have to be controlled in interests of all, else the power of this new potential blessing , food for all mankind from 'waste' CO2 that would otherwise possibly destroy us , could end up making things far worse for some, many or all...

    I think then that the CO2 crisis , when finally unravelled from the short-sighted vested interests of the few who think they like wars, hoardes of money, control of others , and think complacently that they have the means to face any crisis, has enormous potential to re-unite mankind , just as man was united no doubt by the crisis that limited our genetics so many millenia ago ... not without first a period of extreme stress caused by inertia to acting wisely - but the prize might be mankind as one species , coming to realise we have but one home , and worthy of respect from us, not the abuse we deal out today in our ignorance and complacency...

    I thus applaud loudly the work of this site, it is awesome in the way it translates complex interactions into words that folks who are not specialists can come to grips with , a massive resource that surely must break down interdisciplinary barriers holding up the uniting of the people into demanding an end to the wars, inequalities, injustices, and sheer inadequate caring of nations with 'power' ... aprocess which must start with establishing the TRUTH first and then disseminating it worldwide to unite men in facing the massive problem we all have , but which is struggling to be acknowledged amongst a mass of false propaganda and much misunderstanding and misinterpretation...

    Awesome my friends, so much 'uphill' work in perhaps the greatest challenge to mankind yet .... becoming one species again and saving our planet [from our division] by means of coming nearer to the truth :) !

    Comment by Roger William Chamberlin — 10 Jul 2007 @ 9:31 AM

  206. Re #24:

    The 2.8C temperature increase due to global warming seems to be an exaggeration. Compare the average temperature of a non-greenhouse gas body (the moon) to a greenhouse gas body (the earth). The average temperature of the moon is 238K The average temperature of the earth is 288K. The difference is 50K. Therefore, the 1% should be measured off of 50K instead of 285K. That results in a 0.5K increase in temperature, not 2.8K.

    Also, the stratospheric cooling effect has me confused. If the stratosphere is cooling, then that causes the troposphere to warm, right? well, the troposphere greenhouse gas composition is dominated by water vapor, not CO2. So why would such a small increase in overall greenhouse gases make a big difference?

    Comment by Dean — 12 Jul 2007 @ 9:42 AM

  207. Re #206: Dean — There is a feedback effect. This is described, in fairly simple terms, in earlier threads. I also encourage looking at the AIP history site, linked on the sidebar, and some of the highlight threads, also linked on the sidebar, here on RealClimate.

    Comment by David B. Benson — 12 Jul 2007 @ 7:38 PM

  208. Dean, no, the 1% is of the total incident sunlight–not the radiation that causes the greenhouse effect.

    Comment by ray ladbury — 12 Jul 2007 @ 8:28 PM

  209. [[The 2.8C temperature increase due to global warming seems to be an exaggeration. Compare the average temperature of a non-greenhouse gas body (the moon) to a greenhouse gas body (the earth). The average temperature of the moon is 238K The average temperature of the earth is 288K. The difference is 50K. Therefore, the 1% should be measured off of 50K instead of 285K. That results in a 0.5K increase in temperature, not 2.8K.]]

    What in the world do you mean here? I’ve read this paragraph several times now and I still cannot figure out what you’re saying. (Your average temperature figure for the Moon is way too low, by the way.)

    Comment by Barton Paul Levenson — 13 Jul 2007 @ 7:05 AM

  210. Okay, Dave, I think I see where you went wrong. You’re assuming the Earth’s temperature would be 238 K without an atmosphere, and that the 50 K difference is due directly to carbon dioxide and is linear, so that a 1% increase in CO2 would yield a 0.5 K increase in temperature. Do I have that right?

    The Earth’s equilibrium temperature is actually 255 K, not 238 K, and the net greenhouse effect amounts to 33 K. But the relation between CO2 and the greenhouse increment is not linear. All kinds of factors combine to set the temperature of the Earth. For instance, the greenhouse effect from Earth’s atmosphere would actually be about 77 K, raising the surface temperature to 332 K, were it not for the fact that evaporation of seawater, convection and conduction cool the surface considerably.

    With all other factors being equal, a doubling of CO2 causes a surface temperature increase on Earth of about 1.2 K (Houghton 2004). Factoring in the known climate-system positive feedbacks, especially the increase in water vapor with ambient temperature, a doubling in practice will be closer to 2.8 K.

    Comment by Barton Paul Levenson — 13 Jul 2007 @ 7:11 AM

  211. Measuring the temperature of the moon is done from the top of Mauna Kea, by infrared astronomers, who have to account for the immediate and variable water vapor along their line of sight as well as much else, so asking the temperature of the moon has some direct relation to the topic. I know I’m stretching (grin).

    This describes that effort and makes clear how complicated the work is: http://hera.ph1.uni-koeln.de/~wiedner/publications/lunareclipse.pdf
    “… The magnitude of the temperature drop observed during the eclipse at 265 GHz (central frequency of the band covered) was about â�¼70 K, in very good agreement with previous millimeter-wave measurements of other lunar eclipses. We detected, in addition, a clear frequency trend in the temperature drop that has been compared to a thermal and microwave emission model of the lunar regolith, with the result of a good match of the relative flux drop at different frequencies between model and measurements.”

    For simple statements, there’s:

    http://www.iop.org/EJ/article/0031-9120/26/3/008/pe910308.pdf
    Physics in the global greenhouse –S Ross – Physics Education, 1991 – iop.org
    “… solar energy) that the Moonâ��s â��effcctive radiating temperatureâ�� should be roughly -18°C. This is indeed the average temperature of the Moon ….”

    and a more recent number:
    Five times more water on Moon? – P BALL – Virus, 2003 – nature.com
    “… the Moon. Dark arts. The average temperature of the Moon’s surface is -23ºC. It gets much warmer in direct sunlight. But in permanently … ” [No working link for that, it's just a Google Scholar hit]

    Comment by Hank Roberts — 13 Jul 2007 @ 11:00 AM

  212. The Solar constant for the moon is the same as for the Earth, 1367.6 W m-2. (This figure is overprecise and probably a bit high, but it’s canonical, so I like to use it.) The moon’s bolometric Bond albedo, according to Bonnie Buratti’s team, is about 0.11. So the flux absorbed by the moon is (1367.6 / 4) x (1 – 0.11) or 304.3 W m-2. This corresponds to an equilibrium temperature of 270.7 degrees K. But the moon rotates very slowly (27.3 days sidereal), so in effect it only radiates from the dayside, 2 π R2 instead of 4 π R2. This would make its dayside temperature, at least, higher by a factor of 20.25, or 321.8 degrees K. I believe Langley in 1890 reported the measured temperature of the Moon as 318 degrees K. Does anyone have a later figure from the primary literature?

    Comment by Barton Paul Levenson — 14 Jul 2007 @ 6:43 AM

  213. Very good presentation and excellent follow-up q&a!

    One thing I would like to see better treated is the concept of convective heat transport. The concept that molecules of water absorb heat and become water vapor, the water vapor rises and cools through adiabatic lapse, releases the absorbed energy, condenses and falls as liquid water is well known by most people. But the parallel process which works with other greenhouse gasses is less understood.

    CO2 gas is opaque to various spectra of long wave infra red and absorbs energy at those frequencies. The absorbed heat makes the gas expand and rise. As the gas rises the pressure decreases with altitude and the gas expands and cools, without the loss of absorbed energy, through dry adiabatic lapse. The infrared frequency at which the gas radiates becomes gradually longer as it rises, expands, and cools. At some point the wavelength will hit a frequency where the gas is relatively transparent and the gas loses the absorbed energy through infrared radiation.

    Between the point where the infrared energy was absorbed near the surface and where it is released at altitude we effectively have convective heat transport. I would be interested in knowing how the rate of convective heat transport is affected by the saturation level of the various greenhouse gasses. I also wonder if we could see CO2, and other greenhouse gasses visibly in the atmosphere, how well defined the bases and tops of the transport cells would be.

    Comment by Dave Embody — 15 Jul 2007 @ 9:38 PM

  214. >Moon
    I found these here: http://www.solarviews.com/eng/moon.htm
    Mean surface temperature (day) 107°C
    Mean surface temperature (night) -153°C
    Maximum surface temperature 123°C
    Minimum surface temperature -233°C

    Handy conversion tool: http://www.csgnetwork.com/temp2conv.html

    And this: http://www.space.com/scienceastronomy/051207_moon_storms.html: “a few hours after every lunar sunrise, the experiment’s temperature rocketed so high–near that of boiling water–that ‘LEAM had to be turned off because it was overheating.’ — apparently duststorms follow the sunrise on the Moon.

    And, very topical, this:
    “NASA acquired 41 monthsâ��worth of records of the Moons surface temperature…..On the near side of the
    airless moon, where Apollo 15 landed, surface temperature is controlled by solar radiation
    during daytime and energy radiated from Earth at night. Huang showed that due to an amplifying effect, even
    weak radiation from Earth produces measurable temperature changes in the regolith. Further, his revisit of the
    data revealed distinctly different characteristics in daytime and nighttime lunar surface temperature variations.
    This allowed him to uncover a lunar night�time warming trend from mid�1972 to late 1975, which was consistent
    with a global dimming of Earth that occurred over the same period and was due to a general decrease of sunlight
    over land surfaces. (Widespread ground�based radiation records from that period show that solar radiation
    reaching Earths surface during that period decreased significantly, for reasons that are not completely
    understood.)
    Huang’s study demonstrated that signals from the energy budget of Earths climate system are detectable on the
    Moon and can be useful in monitoring and predicting climate change…..
    http://www.astrobio.net/cgi-bin/h2ps.cgi?sid=2354&ext=.ps

    Comment by Hank Roberts — 16 Jul 2007 @ 2:52 AM

  215. Dave Embody:

    I also wonder if we could see CO2, and other greenhouse gasses visibly in the atmosphere,

    CO2 concentrations at the mid-tropospheric level (roughly 8km) )at least can be detected by AIRS (via Eli Rabett, which also has many other interesting CO2 links.)

    Comment by llewelly — 19 Jul 2007 @ 6:34 PM

  216. With reference to the piece which started this thread, fifth paragraph, please can somebody tell me the altitude corresponding to “a layer so thin that radiation can escape into space”.

    Comment by AEBanner — 20 Jul 2007 @ 4:48 PM

  217. The original post, including for clarity the full sentence, said:
    “Eventually the energy reaches a layer so thin that radiation can escape into space.”

    That isn’t talking about “all energy” — it’s talking about any given particular bundle, and its chances of escaping.

    They’re following any particular example of a chunk of energy, bouncing around after coming to Earth, in various forms.

    Any chunkj of energy can only leave the planet as radiation (an infrared photon) if it doesn’t first run into another molecule.

    So they’re not specifying a number for altitude — not a single fixed “layer” or a specific height or thinness that applies to each and every photon, not a glass ceiling kind of thing.

    The “altitude corresponding” would be, approximately, “way way up there where the air is very thin” on average.

    Of course if the emitted photon happened to be pointed downward, it would nevertheless hit another molecule — so even at the very “top of the atmosphere” half the photons are not going to escape into space.

    Your altitude will vary for each individual occurrence, of course — but the odds are better the thinner the air is.

    There’ s no Maxwell’s Demon at 90,000 Feet or any other specific altitude.

    Comment by Hank Roberts — 20 Jul 2007 @ 6:13 PM

  218. Thank you, Hank Roberts, for your poetic description of the altitude discussed in paragraph 5 of “A Saturated Gassy Argument”, which started this thread. However, I was asking for some idea of the altitude, not a precise figure.

    In his book “Global Warming – The Complete Briefing”, page19, Fig 2.3, Houghton gives a value of about 6Km for the average altitude at which outgoing radiation occurs. So what value should I take for “way, way up there where the atmosphere is very thin”? 8 Km, 10 Km, 20 Km, or perhaps even 100 Km?

    This could be rather important, because there is a negative effect which depends upon altitude. The greater the altitude, the smaller is the proportion of photons returned to the Earth’s surface, because of the solid angle subtended at any given emitting point by the circle on the Earth’s horizon, as seen from that altitude.

    The following table shows the reduction in the returned proportion for the given altitudes compared with the proportion for zero altitude.

    Altitude___Proportion of total___Reduction in
    Km _______returning to Earth ___proportion

    0___________0.50______________0%
    6___________0.48______________4%
    10__________0.47______________6%
    20__________0.46______________8%
    50__________0.44_____________12%
    100_________0.41_____________18%

    It follows that if the altitude “way, way up there” in order to achieve the required “thinness” is significantly higher than Houghton’s 6 Km, then the reduction in proportion may well exceed the postulated increase in energy returned from doubling carbon dioxide. This would mean that the Saturated Gassy Argument fails or, at least, is significantly diminished.

    AEB

    Comment by AEBanner — 21 Jul 2007 @ 12:06 PM

  219. You’re making the mistake of assuming no atmosphere, calculating angles subtended by the solid planet.
    The number you want is how far a photon on average will go before it interacts with a molecule.

    Comment by Hank Roberts — 21 Jul 2007 @ 12:44 PM

  220. AEBanner (#217) wrote:

    In his book “Global Warming – The Complete Briefing”, page19, Fig 2.3, Houghton gives a value of about 6Km for the average altitude at which outgoing radiation occurs. So what value should I take for “way, way up there where the atmosphere is very thin”? 8 Km, 10 Km, 20 Km, or perhaps even 100 Km?

    It follows that if the altitude “way, way up there” in order to achieve the required “thinness” is significantly higher than Houghton’s 6 Km, then the reduction in proportion may well exceed the postulated increase in energy returned from doubling carbon dioxide. This would mean that the Saturated Gassy Argument fails or, at least, is significantly diminished.

    The troposphere extends from 8 km to 14.5 km. As I understand it, water vapor dominates from the ground only to about 4 km, if I am not mistaken. Carbon dioxide (and ozone) dominate after that. But the stratosphere itself constitutes approximately 25% of the earth’s atmosphere. So I wouldn’t assume that the greenhouse effect ends at the tropopause, or that the atmosphere becomes so thin at this point that it no longer matters – although I would certainly defer to someone who I regarded as more knowledgable than myself.

    From what I understand, Local Thermodynamic Equilibrium is a fair approximation for most of the relevant wavelengths except when one gets to the outer reaches of the stratosphere – and I would regard this as relevant. And it is worth keeping in mind the fact that as more carbon dioxide is added to the atmosphere, this tends to raise the both the tropopause and the effective radiating layer, the latter of which is that which emits radiation at the temperature which the earth would radiate in the absence of an atmosphere.

    Additionally, as I see things, it makes little sense to whatsoever to argue that there is an exact boundary at which carbon dioxide has no effect because it is “completely saturated” (it never is) to suddenly being unable to absorb any radiation at all. In fact, there is no point that it is completely saturated – although its effects are quite insignificant at ground level given the moisture in the air. There is the diminishing spreading due to pressure and temperature as one ascends, but assuming the atmosphere becomes dry before this, carbon dioxide can and will play a role that grows with higher partial pressures. Additionally, it is my understanding that carbon dioxide is directly responsible for roughly a third of the marginal greenhouse effect and that this is a conclusion which has a fair amount of empirical support.

    In any case, I believe that Houghton was refering not to the point at which outgoing radiation last encounters molecules but rather what known as the effective radiating layer. This is the point at which the net effect of carbon dioxide is to cool the atmosphere at that altitude, radiating thermal more thermal energy in the direction of space than it radiates towards the ground. However, much of the radiation which it radiates will still be in the direction of the ground.

    Additionally, as more carbon dioxide is added to the atmosphere, this will tend to raise the effective radiating altitude, and holding the lapse rate constant (not entirely accurate, but a fair approximation – see Tamino’s post “Lapse Rate” at Open Mind), this will result in more greenhouse gas prior to the effective radiating layer, increasing the greenhouse effect experienced at the surface.

    I hope this helps…

    Comment by Timothy Chase — 21 Jul 2007 @ 3:12 PM

  221. Thank you, Hank Roberts, for your contribution #219, but I find it difficult to see your point. Atmosphere or not, there will only be extra surface warming from additional CO2 if the photons return to the surface in line with the standard explanation of the GH effect, and to do this they must be confined to the solid angle governed by the altitude as in the table in my #218. Hence, there will be a reduction, or even a cancellation, of the extra warming from additional CO2 at “high” altitudes.

    The amount of this negative effect depends on the altitude, and hence my interest in it. Surely, some expert in these matters must know, at least, a rough figure for this. Please help.

    Comment by AEBanner — 21 Jul 2007 @ 3:46 PM

  222. AEBanner (#221) wrote:

    Thank you, Hank Roberts, for your contribution #219, but I find it difficult to see your point. Atmosphere or not, there will only be extra surface warming from additional CO2 if the photons return to the surface in line with the standard explanation of the GH effect, and to do this they must be confined to the solid angle governed by the altitude as in the table in my #218. Hence, there will be a reduction, or even a cancellation, of the extra warming from additional CO2 at “high” altitudes.

    At the very least, I believe you are making a number of mistakes. One of the lesser mistakes would appear to be the belief that a photon gets absorbed only once.

    And as I pointed out in the second to last paragraph of #220, I believe you are misinterpretting Houghton, specifically by assuming that when he speaks of the altitude at which thermal energy escapes, he means that photons never get absorbed after that. As I stated, I believe that he is refering to the effective radiating altitude – which is the height at which the greenhouse effect begins to radiate more energy towards space than it does towards the ground. This is the height at which the atmosphere has the effective radiating temperature – which is what the temperature of the earth would be in the absence of an atmosphere (holding the albedo the constant).

    However, much of the radiation which is re-emitted above this altitude will still be re-emitted towards the ground and be absorbed by the ground, increasing the greenhouse effect as it is experience at ground level. Likewise, raising the level of carbon dioxide will tend to raise the altitude of the effective radiating layer. Holding the lapse rate constant, this will increase the height of the air column prior to the effective radiating layer resulting in an increase in the greenhouse effect and consequent warming at ground level.

    I could say more, but I believe I already have.

    Comment by Timothy Chase — 21 Jul 2007 @ 4:21 PM

  223. Re 221: I think Hank’s point is that a photon which returns to earth will typically be the result of many absorptions and readmissions following the emission of the original photon from the surface of the earth. Thus, an interaction at high altitude will not necessarily require that the emitted photon be within the solid angle subtended by the earth. Even if it is emitted upward, it may encounter a molecule that, in effect, redirects it toward the earth. Have I got this right?

    Comment by Ron Taylor — 21 Jul 2007 @ 4:23 PM

  224. Ron Taylor (#223) wrote:

    Re 221: I think Hank’s point is that a photon which returns to earth will typically be the result of many absorptions and readmissions following the emission of the original photon from the surface of the earth. Thus, an interaction at high altitude will not necessarily require that the emitted photon be within the solid angle subtended by the earth. Even if it is emitted upward, it may encounter a molecule that, in effect, redirects it toward the earth. Have I got this right?

    That is exactly what Hank Roberts (#219) is arguing – and that is really the most essential point. But what would seem to be the central problem is a misunderstanding of Houghton, namely that he holds that photons tend to escape without interacting with the atmosphere at 6 km or above. What I believe Houghton holds is that this is the altitude of the effective radiating layer, and as a matter of fact, Gavin mentions that the altitude of the effective radiating layer is roughly 6 km in an earlier essay:

    In the case of the Earth, the solar input (and therefore long wave output) are roughly constant. This implies that there is a level in the atmosphere (called the effective radiating level) that must be at the effective radiating temperature (around 252K). This is around the mid-troposphere ~ 6km. Since increasing GHGs implies an increasing temperature gradient, the temperatures must therefore ‘pivot’ around this (fixed) level. i.e. everything below that level will warm, and everything above that level will cool.

    Why does the stratosphere cool when the troposphere warms?
    7 December 2004
    http://www.realclimate.org/index.php?p=58&langswitch_lang=en

    Some of the energy re-emitted at this level and above will still be redirected towards the surface thereby increasing the surface temperature. However, the net effect of carbon dioxide at this level and above will be to cool the layer which is in. In contrast ozone will tend to absorb ultraviolet, warming that layer of the atmosphere.

    PS

    Correction to my earlier post: the net effect of carbon dioxide somewhat below the effective radiating level is no doubt to cool those layers. The effective radiating level is simply the level at which the temperature is equal to what it would be in the absence of any greenhouse effect.

    Comment by Timothy Chase — 21 Jul 2007 @ 5:26 PM

  225. PS to 224

    It should be noted that despite what I quoted from Gavin, the effective radiating level isn’t fixed. He later acknowledges as much in the discussion which comes afterwards, but had been relying upon someone else’s calculations. However, he left it in partly because it preserved the continuity of the discussion. As is later noted, the effective radiating level rises with increased levels of carbon dioxide. This is something which is also dealt with Tamino’s “Lapse Rate” and Archer’s book.

    Interestingly, another point which comes during the discussion which follows Tamino’s essay is that the tropopause rises as well as the result of increased levels of carbon dioxide. This is something which was predicted by the models but which has also been observed.

    Comment by Timothy Chase — 21 Jul 2007 @ 6:48 PM

  226. > extra warming if photons return to the surface
    Nope, the extra warming persists because the photons, or the energy they represent in other forms, are staying in play in the atmosphere. A photon emitted at 6km may be more likely than not to escape the planet if it’s emitted upward, which I believe is the point being made about that altitude. But as mentioned, this is changin, as was predicted by modelers
    http://adsabs.harvard.edu/abs/1987JGR….9210897C
    and later observed http://www.sciencemag.org/cgi/content/abstract/301/5632/479

    Hmmm, I miss the “preview” function, which was useful to check whether the links actually work. That first one should take you to:
    On the depletion of ozone by a height increase of the tropical tropopause
    Chimonas, George
    Journal of Geophysical Research, Volume 92, Issue D9, p. 10897-10902 09/1987
    1987JGR….9210897C

    Comment by Hank Roberts — 21 Jul 2007 @ 7:56 PM

  227. >tropopause rises, predicted and observed
    http://www.llnl.gov/str/March04/Santer.html
    http://www.sciencemag.org/cgi/content/abstract/301/5632/479

    Mr. Banner wrote, I believe incorrectly:
    “there will only be extra surface warming from additional CO2 if the photons return to the surface …”
    Nope. The photon may exist only for a fraction of a second before it gets absorbed. The molecule that absorbed it may be bumping and grinding before some other molecule gets enough energy for long enough to emit another photon. That’s all the same energy.
    The energy takes many forms, it doesn’t stay as a photon or have to hit the surface to be contributing to surface warming. As long as the energy hasn’t escaped to space it is still here in one form or another.

    Comment by Hank Roberts — 21 Jul 2007 @ 8:42 PM

  228. [[Atmosphere or not, there will only be extra surface warming from additional CO2 if the photons return to the surface in line with the standard explanation of the GH effect,]]

    Not true. Warming at any level affects all the other levels, even if not directly. Let me know if you want a mathematical example.

    Comment by Barton Paul Levenson — 22 Jul 2007 @ 6:47 AM

  229. Although we know about the increased absorbtion of energy by CO2, it still remains the case that this varies logarithmically with CO2 concentration; what this article explores is a change in the constant in front of the logarithm of CO2 concentrations in our calculation of energy absorbtion.
    And that means that I still can’t buy the global warming scare.
    We’ve been experiemnting with CO2 in the atmsophere for a long time now, we don’t need fancy models. Let’s assume that we’ve observed 0.7 C of warming since 1940, during which time CO2 levels have risen from 290 to 380 ppm. The IPCC claims ’90 % certainty that 50 % of the warming observed to date has been caused by emissions of CO2′. Fine, let’s accept that, so that’s 0.35 C warming due to CO2. Since CO2 is a logarithmic effect, we can now predict what would happen if we doubled up the CO2 to 780 ppm (a prodigous amount, probably not even possible with our current oil reserves). The amount of warming would then be given by
    0.35*ln(760/380)/ln(380/290)
    The proportionallity constants drop out.
    That works out at 0.9 C. Not 6 C, not 4 C, not even 2 C. But less than 1 C.
    But what about the feedback mechanisms? Well, they all apply as of now, and have done since 1940, so they’re built into the calculation I’ve just done.
    What about thermal inertia – perhaps we haven’t seen the full effects of the 380 ppm we’ve already dumped in the atmosphere. Perhaps we haven’t. although 60 years is a long time. But whatever inertia we’ve experienced in the past will apply to the future as well, so we can say that within 60 years from now, the max temperature rise will be less than a degree.

    [Response: The statement from the IPCC is not correct; the planet is responding to the net forcing, not just CO2; thermal inertia implies that a transient result can't be extrapolated to equilibrium responses, etc. Bottom line: you are attempting to calculate cliamte sensitivity from the 20th Century trend, but as we've discussed many times, that is not much of a constraint because of the uncertain influence of aerosols and the ocean uptake of heat. It would be nice if it was that easy, but the reality is that it isn't. - gavin]

    Comment by Capell Aris — 23 Jul 2007 @ 10:53 AM

  230. Capell Aris — where do you find this statement you say you are quoting from the IPCC? Gavin says it’s not correct; I wonder if it’s even from the IPCC at all. Cite please?

    Comment by Hank Roberts — 23 Jul 2007 @ 12:31 PM

  231. I have to admit that I’m struggling to find the IPCC reference. I thought it came from the briefing for the latest report, but I can no longer find that on their website. I would therefore be quite willing to accept a corrected percentage figure.

    However, I cannot agree with Gavin
    (i) I believe I’m extrapolating a trend of over sixty years that gives us ample time to see all the effects, to date, of aerosols and the uptake of ocean heat. There may be changes in how some of these variables behave in the future, but those chnages should be second order. (The world temperature is only changing by a fraction of a percent. I agree, that if we confine our scope of interest to the temperature/pressure range for water then the percentage is higher, but it’s still only about a percent). This simple analysis demonstrates VERY powerfully, that predictions of temperature rises of 6 C are absurd, simple scaremongering.
    (ii) thermal inertia remains a constant. If it applies to the observations over the past 60 years, it will apply with equal force in the future.
    (iii) I appreciate that we’re adding a series of stimulii each of which will create an exponential temperature rises, but again, the accuracy of the simple calculation will not be greatly affected by considering them as two step changes. Yes, I agree it may not be ‘this’ simple, but at the same time we cannot postualte changes as high as 6 C merely on the grounds of complexity.

    [Response: You misunderstand the nature of the problem. The key is to define 'climate sensitivity' so that, given estimates of future GHG levels, we can estimate the resulting temperature change. This is not a question of linear extrapolation! So from the 20th C (or the last 60 years), do we have enough information to constrain sensitivity? The answer is no. See this post for a more worked out example for why uncertainties in aerosols and ocean heat uptake matter. However, other constraints on sensitivity put it around 3 +/- 1 deg C for a doubling of CO2. Future temperatures are a convolution of this sensitivity, the actual amount of CO2 rise and the delay due to thermal inertia. 6 deg is only if we max out on both the sensitivity and we end up with high emissions. I don't think it would be describable as a best guess - more a worst case scenario. -gavin]

    Comment by Capell Aris — 23 Jul 2007 @ 2:14 PM

  232. Capell Aris: I’m interested in how you decide that aerosols and ocean heat uptake changes in the future should be “second order”? If, hypothetically, we posit a world in which CO2 concentration is increasing linearly and aerosol emissions are increasing linearly such that they exactly cancel out, and then one day aerosol emissions flatten out, then you go from having _zero_ increase in forcing to continual increase in forcing.

    Now, in our world, CO2 has been increasing linearly, whereas aerosol loading first increased, then flattened out, and we don’t know what it is going to do in the future. I think that’s a first order effect.

    Ocean heat uptake similarly can do odd things: if increased atmospheric heat leads to increased stratification of the top layers of the ocean as they heat up, then that will reduce ocean heat uptake and suddenly you get accelerated heating as the sink disappears (and the ocean sink is important for carbon uptake too).

    Basically, just picking 2 examples can show how flawed your “simple analysis” is. You may want to consider in the future that when a large number of experts overlook what you think is “simple” that perhaps they know something you don’t know. (And we haven’t even addressed other GHGs, volcanoes, and all sorts of other complicating effects)

    ps. We don’t reach 780 ppm with oil reserves alone: that takes coal reserves too, of which there are plenty. Or ecological disaster in the amazonian rainforest, permafrost carbon release, or other such natural event potentially caused by climate change…

    Comment by Marcus — 23 Jul 2007 @ 4:06 PM

  233. Interesting, from: http://www.agu.org/pubs/crossref/2007/2006GL028668.shtml

    “For every 1% decrease in SO2 emissions over Europe and the USA the modelled sulfate column burden decreased by 0.65%, while over Asia a 1% increase in SO2 resulted in a 0.88% increase in sulfate. The different responses can be explained by the availability of oxidant in cloud. We find that because emissions have moved southward to latitudes where in-cloud oxidation is less oxidant limited, the 12% reduction in global SO2 emissions between 1985 and 2000 caused only a 3% decrease in global sulfate.”

    Comment by Hank Roberts — 23 Jul 2007 @ 5:10 PM

  234. Firstly, I wish to thank the several contributors for their helpful replies to my #218. Unfortunately, I seem to have caused confusion about my thoughts on this matter by my reference to Houghton’s figure of 6 Km altitude. I mentioned this figure simply for comparison with the requested values for “way, way up there where the air is very thin” in the “Saturated Gassy Argument”. Sorry for misleading anyone.

    Secondly, please remember that, while fully accepting that global warming is occurring, I am sceptical about increased carbon dioxide being the cause. However, I am ready to be persuaded to this view by appropriate arguments. All I want is the truth of the matter.

    With reference to my argument about the solid angle subtended by the Earth at points emitting at high altitudes, Mr Roberts, supported by others, seems to say, if I have correctly understood, that the energy reaching the Earth’s surface from any given emitting point need not be considered as being constantly within the cone of the solid angle, because the emitted energy, initially electromagnetic, can be transferred to other molecules as kinetic energy, and these molecules can enter the cone by random molecular collisions. Have I got this right?

    However, by the same process in reverse, an equal amount of energy can leave the cone, so cancelling the argument. So we are back to my original point that the amount of energy reaching the surface within the cone reduces as the altitude increases, and the excess escapes into space.

    Comment by AEBanner — 24 Jul 2007 @ 9:10 AM

  235. > the cone of the solid angle …

    No, as I understand it this isn’t a line of sight issue.

    For any emitted photon, what happens to that packet of energy is some probability of being absorbed by a gas molecule.

    That probability changes with elevation/temperature/density and gas mixture at least, probably with other factors too. What else adds and subtracts energy from bond angles, bond vibration, and so forth?

    We know the molecules at the top of the atmosphere are higher and colder recently, as the atmosphere below them expands (observed as predicted). That’s what’s changed in the region from which infrared is effectively leaving the planet — the gas doing the emitting is colder.

    Comment by Hank Roberts — 24 Jul 2007 @ 2:41 PM

  236. Abuse? I believe he’s attempting argument. Let’s check:
    http://www.ibras.dk/montypython/finalripoff.htm#Argument

    Comment by Hank Roberts — 24 Jul 2007 @ 3:42 PM

  237. Re #324: AEBanner — Have you read the AIP history of climatology, linked on the sidebar?

    Comment by David B. Benson — 24 Jul 2007 @ 5:39 PM

  238. Re #237

    Yes. What do you think I’ve missed?

    Comment by AEBanner — 24 Jul 2007 @ 5:45 PM

  239. Well, the AIP history explicitly does not cover developments since the 1980s, which this topic and the associated topic do address. It seems to me what you may be missing is the source of the information used for the work being described:

    “The discussion here is based on CO2 absorption data found in the HITRAN spectroscopic archive. This is the main infrared database used by atmospheric radiation modellers. This database is a legacy of the military work on infrared described in Part I , and descends from a spectroscopic archive compiled by the Air Force Geophysics Laboratory at Hanscom Field, MA (referred to in some early editions of radiative transfer textbooks as the “AFGL Tape”).”
    http://www.realclimate.org/index.php/archives/2007/06/a-saturated-gassy-argument-part-ii

    Comment by Hank Roberts — 24 Jul 2007 @ 5:54 PM

  240. Re #238: AEBanner — The page entitled “The Carbon Dioxide Greenhouse Effect”, perhaps?

    Comment by David B. Benson — 24 Jul 2007 @ 6:45 PM

  241. More on the AFGL Tape:
    http://www.cfa.harvard.edu/atmosphere/publications/ComptesRendus-RothmanEtal-2005.pdf

    Comment by Hank Roberts — 24 Jul 2007 @ 8:40 PM

  242. AEBanner (#238) wrote:

    With reference to my argument about the solid angle subtended by the Earth at points emitting at high altitudes, Mr Roberts, supported by others, seems to say, if I have correctly understood, that the energy reaching the Earth’s surface from any given emitting point need not be considered as being constantly within the cone of the solid angle, because the emitted energy, initially electromagnetic, can be transferred to other molecules as kinetic energy, and these molecules can enter the cone by random molecular collisions. Have I got this right?

    However, by the same process in reverse, an equal amount of energy can leave the cone, so cancelling the argument. So we are back to my original point that the amount of energy reaching the surface within the cone reduces as the altitude increases, and the excess escapes into space.

    Here are some of my thoughts regarding your cone argument.

    1. You are right about a cone being involved, but the point of the cone is not what you “project.” It is not a point at the surface, but at the center of the earth. As such, we are not dealing with a single point on the surface of the earth, or any canceling-out due to photons hopping cones. Given how small the distance is between the earth’s surface and the “surface” of the atmosphere is relative to the distance to the earth’s center, what we are dealing with regarding the volume over which a photon travels is for all intents and purposes a vertical column.
    2. At the time, the column is much taller than you suppose, and the higher the cone the more difficult the difficult the photon will find it to make it from the surface of the earth to space. The photon’s path, given absorption and isotropic re-emission is a random walk and the greater the column height the higher the likelihood that it will make several round trips to the earth’s surface prior to finally escaping to space.
    3. The column height over which carbon dioxide is effective is much higher than you suppose, consisting of all but the last handful of kilometers within the troposphere over which water vapor dominates – and much of the stratosphere.
    4. Adding carbon dioxide to the atmosphere increases the height over which it is effective – largely by raising the tropopause.
    5. You assume that carbon dioxide goes from non-effective due to saturation to non-effective due to being too cold with lines and bands too narrow over a negligible distance. Calculations demonstrate otherwise – the lapse rate is roughly constant. With increased temperatures at the surface of the earth, the distance over which carbon dioxide is effective increases.
    6. Your knowledge of the physics in operation within the atmosphere is minimal and you apparently stand in need of time studying basic and analytic geometry – yet you seem to think that you know more than the vast majority of climatologists spent a fair number of years acquiring a PhD and even more years in the field studying it. Obviously you are quite mistaken.

    Comment by Timothy Chase — 25 Jul 2007 @ 9:53 AM

  243. Re #242 Timothy Chase

    I’m sorry, Mr Chase, but you have completely mis-understood my “analytic geometry”, as you call it. No doubt it’s my fault for not explaining what I meant more clearly.

    By the “acceptable cone”, if I may coin the phrase, I meant the solid angle subtended at the photon emitting point at very high altitude by the circle on the Earth’s surface at the horizon as seen from the emitting point. I’m afraid I cannot express it more simply or concisely. Nothing to do with a point on the Earth’s surface, or at the centre of the Earth, as you seem to think.

    As a result of this mis-understanding, the comments you have just made, #242, are somewhat irrelevant, and I take exception to the view you have taken in your point 6. How do you know what I know about anything? If you have a PhD, as you imply, it surprises and saddens me that you so misread my post.

    If you refer again, more calmly, to my #218, you will see that I have used my “basic” analytic geometry to calculate what I suggested was the “acceptable cone” for a range of altitudes up into the stratosphere, and beyond. This clearly shows a reduction in the solid angle as height increases. So what we need to know is the altitude and the spread of the absorbing region concerned in the explanation of the “Saturated Gassy Argument”.

    So far, the PhD climatologists you refer to have not deigned to offer any figues for these parameters. Therefore, it is almost impossible to evaluate the proposed effect, or indeed to see if the “acceptable cone” has any significant numerical effect.

    Until we have such information, as Hank Roberts would say, “it’s just poetry”.

    Comment by AEBanner — 25 Jul 2007 @ 2:48 PM

  244. Er, no, I’d say it’s just a question of the mean free path on average, and an empirical question how much radiation escapes the planet — and that line of sight doesn’t matter. You’re making much the same argument, I think, that is made by one person who posts here regularly, that the atmosphere has to be transparent to infrared.

    I’ve suggested looking for infrared photographs of the Earth showing the horizon — if the cloud tops mark the top of the atmosphere as photographed in the infrared he’s right. If, however, the upper atmosphere is bright in the infrared above the clouds — which is what the infrared astronomers keep claiming in arguing for funding to put their infrared telescopes on mountaintops, on stratospheric balloons, and in orbit —- then he and you are wrong.

    I’m going with the consensus on this — I think the upper atmosphere is bright (and so foggy) in the infrared, for the reasons explained above, and that line of sight doesn’t constrain where the energy goes.

    Poetry as I use the word here is a serious effort to actually find the best words to explain the math. The math says you’re wrong too.

    Comment by Hank Roberts — 25 Jul 2007 @ 5:25 PM

  245. The replies to my posts about the solid angle subtended by the Earth at points emitting at high altitudes, seem to say, if I have correctly understood, that the energy reaching the Earth’s surface from any given emitting point is not in line of sight, and need not be considered as being constantly within the cone of the solid angle, because the emitted energy, initially electromagnetic, can be transferred to other molecules outside the cone as kinetic energy, and these molecules can enter the cone by random molecular collisions, as in a random walk. Have I got this right?

    I fully accept these statements, but by the same process in reverse, an equal amount of energy can leave the cone, so cancelling the argument. So we are back to my original point that the amount of energy reaching the surface within the cone reduces as the altitude increases, and the excess escapes into space. I tried to make this point previously, but I believe the replies were not really appropriate.

    Comment by AEBanner — 26 Jul 2007 @ 9:20 AM

  246. No. You’re mistaking the solid surface for the Earth.

    The “Earth” is not just the solid part of the planet. The Earth — heating up now — includes everything up to the top of the atmosphere. A photon coming in from outside the system, from the sun, adds to the heat. Energy moving around within the system doesn’t add or subtract, it rearranges. A photon exiting the system into space removes energy, as heat. With a sudden increase in greenhouse gases, this heat flow in and out is out of balance.

    Comment by Hank Roberts — 26 Jul 2007 @ 9:44 AM

  247. AEBanner (#243) wrote:

    Re #242 Timothy Chase

    I’m sorry, Mr Chase, but you have completely mis-understood my “analytic geometry”, as you call it. No doubt it’s my fault for not explaining what I meant more clearly.

    By the “acceptable cone”, if I may coin the phrase, I meant the solid angle subtended at the photon emitting point at very high altitude by the circle on the Earth’s surface at the horizon as seen from the emitting point. I’m afraid I cannot express it more simply or concisely. Nothing to do with a point on the Earth’s surface, or at the centre of the Earth, as you seem to think.

    Agreed.

    I misunderstood you. My apologies. And no, I am not a climatologist.

    I checked, and the figures you’ve given for your line-of-sight “calculation” are accurate. At a hundred kilometers I get 17.51 percent.

    Not that it matters.

    The kind of calculation you’ve made is largely irrelevant. Or to be more precise, it takes into account only one of a variety of factors, not the least of which is the fact that absorption will be increasing along the entire column, not simply at some (somewhat arbitrarily defined) moving endpoint.

    More importantly, I think you misunderstood the point of the two essays: they were not to demonstrate how to perform the specific calculations on paper that climate models perform. They were to demonstrate what was wrong with the view that carbon dioxide is saturated, and therefore increasing the amount of carbon dioxide will have no increased greenhouse effect. In the process of explaining this historical, Ray was able to illustrate the importance of spreading. Simple column calculations are more than enough to get get both points across.

    However, if you seriously wish to claim that increasing the amount of carbon dioxide in the atmosphere will have no increased greenhouse effect, I have a small problem for you: Venus.

    Comment by Timothy Chase — 26 Jul 2007 @ 2:22 PM

  248. AEBanner: Thought experiment: A sphere of CO2 gas floating in space: An infrared light source in the center of the sphere: Does the sphere heat up?

    I think you would agree the answer is yes. And yet… there is _no_ solid object in the middle, so the subtended solid angle would be zero. So this is a problem if you want to argue based on this subtended angle logic that a higher altitude CO2 molecule has a reduced impact on heating up the earth system.

    Comment by Marcus — 26 Jul 2007 @ 2:40 PM

  249. Thank you, gentlemen, for your posts,#246, #247 and #248, and for your efforts in trying to sort out my ideas on the “cone”. I can see that I shall have to do more thinking about this.

    Comment by AEBanner — 26 Jul 2007 @ 5:20 PM

  250. {\Omega}_{e}=2\pi\left[\sqrt[]{\frac{2{R}_{e}h+{h}^{2}}{{({R}_{e}+h)}^{2}}}\right]

    Comment by Timothy Chase — 26 Jul 2007 @ 6:05 PM

  251. Spencer,

    You say, “What happens if we add more carbon dioxide? …the place from which most of the heat energy finally leaves the Earth will shift to higher layers. Those are colder layers, so they do not radiate heat as well.”

    It is my understanding that while temperature decreases with altitudes in the troposphere and lower stratosphere, at the altitudes where IR emission into space occurs temperature increases with altitude, not decreases.

    Could you explain a bit more on this point?

    Comment by Walter Starck — 28 Jul 2007 @ 11:29 PM

  252. [[It is my understanding that while temperature decreases with altitudes in the troposphere and lower stratosphere, at the altitudes where IR emission into space occurs temperature increases with altitude, not decreases.]]

    Well, IR comes from all levels, in differing amounts. But if you want to deal with an average emission level, it is well within the troposphere. Divide the planet’s greenhouse increment (33° K.) by the mean tropospheric lapse rate (6.5° K. km-1) and that height works out to be about 5.1 km. The tropopause is 10-15 km high depending on latitude.

    Comment by Barton Paul Levenson — 29 Jul 2007 @ 6:07 PM

  253. Walter Starck (#251) wrote:

    It is my understanding that while temperature decreases with altitudes in the troposphere and lower stratosphere, at the altitudes where IR emission into space occurs temperature increases with altitude, not decreases.

    Good recall on the structure of the lapse rate.

    However, from the essay:

    What happens if we add more carbon dioxide? In the layers so high and thin that much of the heat radiation from lower down slips through, adding more greenhouse gas molecules means the layer will absorb more of the rays. So the place from which most of the heat energy finally leaves the Earth will shift to higher layers. Those are colder layers, so they do not radiate heat as well. The planet as a whole is now taking in more energy than it radiates (which is in fact our current situation). As the higher levels radiate some of the excess downwards, all the lower levels down to the surface warm up. The imbalance must continue until the high levels get hot enough to radiate as much energy back out as the planet is receiving.

    The process is taking place in the upper troposphere. The effective radiating layer is at approximately 6 km, which is considerably below the tropopause, and therefore the atmosphere is still getting cooler the farther you climb. The process whereby the upper troposphere heats up until it is able to radiate away thermal radiation as quickly as the thermal radiation is entering the system results in a lag – which is a large part of the reason that, even if we were to stop emitting carbon dioxide today, it would still take some time before the temperature leveled out at its new equilibrium value.

    Anyway, no worries, mate: I made a closely related mistake only a couple weeks ago, I believe.

    Comment by Timothy Chase — 30 Jul 2007 @ 12:10 AM

  254. PS to #252

    Incidently, when the new equilibrium is achieved, the effective radiating layer will be at a higher level, and per Tamino, given the nearly constant lapse rate (i.e., linear drop in temperature with altitude) in the troposphere, implies that the surface must be warmer if the effective radiating layer is to be at the same temperature as before – where the effective temperature is the temperature at which the earth must radiate thermal radiation (as seen at a distance) in order to be in balance with the rate at which thermal radiation is entering the system.

    Comment by Timothy Chase — 30 Jul 2007 @ 12:23 AM

  255. Re: A Saturated Gassy Argument

    Initially, I was not convinced by this article, which maintained that absorption of photons at high altitudes by increased carbon dioxide could cause a rise in the surface temperature of the Earth. However, on reflection, I thought it would be interesting to attempt to calculate the magnitude of the effect, if any.

    I used a C program which incorporated the Planck distribution and the Stefan-Boltzmann Law. Infrared absorption cross sections for carbon dioxide were obtained from Hitran, and the graph showing Absorption Factor against wavelength, given in Part 2, “What Angstrom didn’t know”.

    Hitherto, I had assumed that there was total absorption of the energy radiated from the surface in the CO2 regions of the spectrum by the CO2 itself and the water vapour, and so no increase in CO2 concentration could produce further heating. However, energy balance considerations with the C program showed that this would cause too much surface heating because of the GH effect of the water vapour. In order to get the surface temperature down to 288.0 K, only about 86% of the emitted energy could be absorbed by the water. So about 14% of the energy would be transmitted to higher altitudes.

    Now the only energy which can be absorbed at high altitudes is the energy of the “wings”, or side bands, of the CO2 region, namely the wavelengths 10, 11 and 12 microns, and 17, 18 and 19 microns. The absorption cross sections for these wavelengths is very small, even at sea level, and the air density is also decreasing with altitude, so further reducing the probability of absorption. Therefore, the overall effect of this postulated high altitude absorption has only a very minimal effect on surface temperature. The results of the calculations are given below, for a doubling of CO2.

    Altitude_____Surface Temp.
    (Km)________Rise deg C

    10___________0.09
    20___________0.02
    30___________0.01

    Comment by AEBanner — 30 Jul 2007 @ 11:13 AM

  256. Re 255 AEBanner: “Now the only energy which can be absorbed at high altitudes is the energy of the “wings”, or side bands, of the CO2 region”

    But as altitude increases water vapor decreases while CO2 remains well mixed, thus CO2 becomes the dominant absorber in the entire active band, not just in the wings.

    Comment by Jim Eager — 30 Jul 2007 @ 10:00 PM

  257. AEBanner (#255) wrote:

    In order to get the surface temperature down to 288.0 K, only about 86% of the emitted energy could be absorbed by the water. So about 14% of the energy would be transmitted to higher altitudes.

    Can the same photon get absorbed only once?

    Comment by Timothy Chase — 30 Jul 2007 @ 11:06 PM

  258. [[I used a C program which incorporated the Planck distribution and the Stefan-Boltzmann Law. Infrared absorption cross sections for carbon dioxide were obtained from Hitran, and the graph showing Absorption Factor against wavelength, given in Part 2, “What Angstrom didn’t know”.

    Hitherto, I had assumed that there was total absorption of the energy radiated from the surface in the CO2 regions of the spectrum by the CO2 itself and the water vapour, and so no increase in CO2 concentration could produce further heating. However, energy balance considerations with the C program showed that this would cause too much surface heating because of the GH effect of the water vapour. In order to get the surface temperature down to 288.0 K, only about 86% of the emitted energy could be absorbed by the water. So about 14% of the energy would be transmitted to higher altitudes.]]

    The atmosphere isn’t wholly radiative. At the surface and near it, convective effects are very important. If you match the radiative effects alone to a surface temperature of 288° K., you’ll get the wrong answer.

    What you appear to be trying to do is write a column model of Earth’s atmosphere. The simplest kind of such model that is reasonably realistic is called a radiative-convective model, and they can be quite complicated. If you’re interested I can send you a (very rough) first draft of a book on writing such models that I’m working on. All the code is in Fortran, but that shouldn’t be too hard to convert to C. The math is almost all the same, except that Fortran has an exponentiation operator and C doesn’t (a big drawback of C, in my view).

    Comment by Barton Paul Levenson — 31 Jul 2007 @ 6:06 AM

  259. Re #257 Yes, a photon can only be absorbed once, but some visible photons, especially blue ones, can be scattered several times.

    Comment by Alastair McDonald — 31 Jul 2007 @ 11:55 AM

  260. I have read the Myhre paper that establishes the Radiative Forcing equation for GHG’s. It is a simple equation that is still widely accepted today.

    I also have just enough spectroscopy knowledge to be dangerously ignorant. It is this ignorance that leads me to ask questions.

    1. Do the Einstein Coefficients (Absorption, Spontaneous Emission, and Stimulated Emissions) need to be taken into account when determining the radiative forcing of CO2? They weren’t in Myhre (as far as I can tell, anyway).

    2. Does Beers law need to be taken into account? As photons travel through a medium they can be absorbed or induce stimulated emission, which will reduce the intensity of the radiation as distance from radiation source increases.

    Would these two factors have any appreciable factor on the radiative forcing of the GHG’s? Why or why not?

    Like I said, I have just enough knowledge to be stupid.

    Comment by mg — 31 Jul 2007 @ 12:15 PM

  261. > a photon can only be absorbed once

    The photons aren’t somehow stored and then released again.
    Nor do they disappear.
    The energy changes form. The molecule can emit another photon, if the energy isn’t transferred in some other way.

    Comment by Hank Roberts — 31 Jul 2007 @ 12:44 PM

  262. Re #256, Jim Eager wrote: “But as altitude increases water vapour decreases while CO2 remains well mixed, thus CO2 becomes the dominant absorber in the entire active band, not just in the wings.”

    As I understand it, the GH effect works by absorption of infrared photons mainly by CO2 and water vapour, and then by re-emission of new photons of corresponding energies, with 50% going down to the surface and producing extra heating, and 50% going upwards and escaping to space. In the process, many more intermediate absorptions and emissions may occur, but the overall, final result is 50% to Earth and 50% to space.

    In my program for #255, I dealt with the effects of CO2 at wavelengths from 13 through 16 microns, with large cross sections, at the equivalent of low altitudes, and so this left only the wings to be dealt with at high altitudes. The absorption cross sections of CO2 are small, or very small, for the wavelengths in the wings and so the corresponding photons could “slip through”, in the words of the initiating essay, to high altitudes.

    The main point to remember, I think, is that once any particular wavelength has been dealt with, that is with 50% of the photons going down and 50% going upwards, you do not repeat the process for that wavelength.

    Comment by AEBanner — 31 Jul 2007 @ 5:54 PM

  263. > As the higher levels radiate some of the excess downwards,
    > all the lower levels down to the surface warm up. The imbalance
    > must continue until the high levels get hot enough to radiate as
    > much energy back out as the planet is receiving.
    — from the original post

    Comment by Hank Roberts — 31 Jul 2007 @ 7:54 PM

  264. Re 262 AEBanner: “The main point to remember, I think, is that once any particular wavelength has been dealt with, that is with 50% of the photons going down and 50% going upwards, you do not repeat the process for that wavelength.”

    Why not, since the 50% that go down can be absorbed and then re-emitted (as new photons), with 50% of them going back up?

    Comment by Jim Eager — 31 Jul 2007 @ 10:18 PM

  265. The temperature of the gas limits the wavelength and energy of the photons emitted.

    Comment by Hank Roberts — 31 Jul 2007 @ 11:15 PM

  266. AEBanner (#262) wrote:

    As I understand it, the GH effect works by absorption of infrared photons mainly by CO2 and water vapour, and then by re-emission of new photons of corresponding energies, with 50% going down to the surface and producing extra heating, and 50% going upwards and escaping to space. In the process, many more intermediate absorptions and emissions may occur, but the overall, final result is 50% to Earth and 50% to space.

    The main point to remember, I think, is that once any particular wavelength has been dealt with, that is with 50% of the photons going down and 50% going upwards, you do not repeat the process for that wavelength.

    Let’s see. You are leaving convection out of the process altogether and wondering why you are getting too much surface heating (#255) so you are reducing absorption by water vapor down to 86% (ibid.) when in reality its about 100%, you are assuming that any longwave at the relevant wavelengths which gets absorbed by water vapor and emitted towards space doesn’t get re-absorbed along the way and then wondering why doubling carbon dioxide has little or not effect upon the greenhouse effect…. I would assume that in your model, when radiation gets emitted towards the ground and then absorbed at ground level it gets re-emitted towards space…?

    The greenhouse effect is a feedback process.

    We don’t just assume that once some radiation has been absorbed then re-emitted its out of play. If one did that, no wonder, in one’s model, the upper layers couldn’t possibly be effective. And just as radiation which is absorbed by the atmosphere and re-emitted to the ground will get re-emitted as thermal radiation which may once again be absorbed by the atmosphere and re-emitted towards the ground, but with a smaller and smaller proportion every time, radiation may be absorbed and re-emitted in both directions at each layer of atmosphere.

    This is part of the feedback process. Even with Gavin’s simple model from a little while ago which consisted of a single layer of paper-thin atmosphere, I had to go through something in the neighborhood of sixty generations before the values finally settled down – and thats part of the process through which one identifies how the system settles down to an equilibrium and what that equilibrium is with the thermal radiation entering the system being balanced by the thermal radiation which was leaving the system.

    And once you start dividing the atmosphere up into layers, you will have feedback between the different layers. If you throw it away as being just too messy, then you aren’t really modeling the greenhouse effect. But you will also want to track their temperatures, thermal expansion, etc..

    Comment by Timothy Chase — 1 Aug 2007 @ 2:09 AM

  267. PS to 266

    I guess the following might help in getting across my point – otherwise it might seem that I am simply trying to make things overly complicated.

    To treat things as if the thermal radiation as if upon its first absorption and re-emission, it either goes immediately to the ground or to space on the reasoning that this is where it must eventually go is only one step removed from modeling the greenhouse effect with thermal radiation being emitted by the ground and going immediately into space on the reasoning that it must eventually reach space, no matter how complicated things may be before it gets there. But of course, the latter approach would mean that thermal radiation didn’t interact at all with the atmosphere, in which case there wouldn’t even be so much as the simplest pretense at modeling the greenhouse effect.

    To model the greenhouse effect, one has to have the feedback between the ground and the atmosphere. But if one wants to model the greenhouse effect in such a way that one is modeling the role of water vapor and the role of carbon dioxide, then one needs at a minimum two layers of atmosphere, the first consisting of water vapor, the second higher layer consisting of carbon dioxide, and then feedback between the ground and the water vapor layer, and feedback between the carbon dioxide layer and the water vapor layer. But this will give you too strong a greenhouse effect if you don’t include convection. And even then, one isn’t getting any of the dynamic evolution of the system if one doesn’t include the warming and thermal expansion of the layers.

    Anyway, I haven’t gotten that far as of yet. However, one thing to keep in mind before you go too far rolling your own: Nasa makes available its models for free – with all of the source code. I believe that is standard operating proceedure in climatology. You get the model and you can examine or even modify the formula to see what the consequences are. The only thing is that these models are fairly large. They had been weighing in at 100,000 lines, but the more recent versions are in the neighborhood of a million.

    Comment by Timothy Chase — 1 Aug 2007 @ 3:20 AM

  268. Re #264 Jim Eager

    The absorption and emission process can occur many times, but the overall effect is still 50% up and 50% down. I think that a program should deal with this once only.

    Comment by AEBanner — 1 Aug 2007 @ 6:09 AM

  269. AEBanner–In science a model needs to be as simple as possible–and no simpler. Your model throws off some very important physics–like convection and conduction, evaporation. These are the main modes of heat transfer in the troposphere. Because of this, the upper troposphere is much warmer than it would be otherwise. It is mainly in the upper troposphere and into the stratosphere that radiation becomes dominant.
    Because the atmosphere is cooler at this altitude, emission in the IR is significantly lower. Moreover, if you add CO2, more of the IR radiated from the lower warmer regions of the atmosphere is absorbed. Some of it is then re-radiated (50% up and 50% down, but some of it goes into heating the atmosphere by collisional relaxation–another process you ignore. Ultimately, it comes down to conservation of energy–if energy isn’t escaping, it is warming the planet until a new equilibrium is reached.

    Comment by Ray Ladbury — 1 Aug 2007 @ 9:05 AM

  270. Well, everyone is entitled to their own beliefs.

    This may be valid as historical re-enactment of the stages in the AIP History. Seems you’re around the era when people had not yet understood the reason there’s a lag time of centuries after increasing CO2 before the planet comes back to equilibrium at a higher temperature?

    Comment by Hank Roberts — 1 Aug 2007 @ 9:40 AM

  271. OK, I’ve thought some more, and I now accept the reasoning of the Saturated Gassy Argument. I wish to thank the several people who have replied to my comments, particularly Timothy Chase, for the help they have extended to me to get my ideas on the right track. My thanks also to Mr Levenson for the offer of a draft copy of his forthcoming book, but I fear it would be far too advanced for my present needs. I retract my #255 and any other negative comments.

    Two questions.
    Can someone please give a figure for the surface temperature rise for a doubling of CO2?

    How does the rate of emission of photons from a gas depend on temperature? Ie. Does it follow Stefan-Boltzmann, as for a solid, black body?

    Comment by AEBanner — 6 Aug 2007 @ 10:17 AM

  272. First question:
    > Can someone please give a figure for the surface temperature
    > rise for a doubling of CO2?

    That’s a definition of “climate sensitivity” (as it will be measured at the end point of the process, after centuries, once the whole system is at radiative equilibrium again). You can find the range of estimates by searching.

    Second question:
    http://www.google.com/search?q=How+does+the+rate+of+emission+of+photons+from+a+gas+depend+on+temperature%3F

    Comment by Hank Roberts — 6 Aug 2007 @ 12:31 PM

  273. The short name for “surface temperature change for a doubling of CO2″ is climate sensitivity. IIRC, the IPCC gives a range of 1.9 to 4.5 degrees C, with the most likely value being 2.8-3.0.

    Comment by Tim McDermott — 6 Aug 2007 @ 1:47 PM

  274. On arguments for clean coal, this has policy implications:

    http://www.iht.com/articles/2007/07/31/america/nuke.2-106441.php
    “The little-noticed provision in the Senate bill refines and expands the loan guarantee program that Congress passed in the Energy Policy Act of 2005…. the bill essentially allows the Department of Energy to approve as many loan guarantees as it wants for both new nuclear plants and those that use other “clean” technologies.”

    So this research may suggest moving the definition of “clean” for coal plants to mean only those run as closed cycle plants.

    Comment by Hank Roberts — 6 Aug 2007 @ 2:06 PM

  275. Dang, wrong thread. That belonged in the current Ozone thread. Ah well.

    Comment by Hank Roberts — 6 Aug 2007 @ 2:47 PM

  276. [[Can someone please give a figure for the surface temperature rise for a doubling of CO2?]]

    If all else is equal, doubling CO2 should cause a radiative forcing of about 3.7 watts per square meter. With a climate sensitivity of 0.75° K. per watt per square meter, this would correspond to a 2.8° K. rise in surface temperature. Both figures are a little shaky. For more on climate sensitivity, I have a web page full of estimates through a link off my main climatology page:

    http://members.aol.com/bpl1960/Climatology.html

    [[How does the rate of emission of photons from a gas depend on temperature? Ie. Does it follow Stefan-Boltzmann, as for a solid, black body?]]

    Usually not; it would be far greater at or around the location of emission lines and near-zero between. But you can use the Stefan-Boltzmann law by chopping up the spectrum into bands and assigning a different (appropriate) emissivity factor between 0 and 1 to each band. Thus a mass of carbon dioxide would have an emissivity around 1 near 14.99 microns but near 0 around 1.0 microns.

    Comment by Barton Paul Levenson — 7 Aug 2007 @ 7:23 AM

  277. AEBanner,

    My apologies for not having read your earlier posts more carefully. I had assumed all too quickly that someone had come in who was merely interested in attacking the science rather than someone who genuinely seeking to understand. Had I read the posts more carefully, I believe I would have noticed that you had put some real thought into this. I will endeavor not to make that mistake again.

    Comment by Timothy Chase — 7 Aug 2007 @ 9:08 AM

  278. I found this passage recently in a piece from the Energy Information Administration of the US Department of Energy

    http://www.eia.doe.gov/cneaf/alternate/page/environment/appd_a.html

    “What happens after the GHG molecules absorb infrared radiation? The hot molecules release their energy, usually at lower energy (longer wavelength) radiation than the energy previously absorbed. The molecules cannot absorb energy emitted by other molecules of their own kind. Methane molecules, for example, cannot absorb radiation emitted by other methane molecules. This constraint limits how often GHG molecules can absorb emitted infrared radiation. Frequency of absorption also depends on how long the hot GHG molecules take to emit or otherwise release the excess energy.”

    Surely, this cannot be correct?
    Please can someone advise?

    Comment by AEBanner — 8 Aug 2007 @ 12:00 PM

  279. Re 278. The first 3 DOE sentences are valid. The rest is true but irrelevant since it is not constraining on the total process.
    When the CO2 absorbs the energy & returns it to the air mostly by collisions but a little by re-emission, (once a hot CO2 collides once, then it loses enough energy that it canNOT reemit a photon of the specific wavelength that can be absorbed by another CO2) the surrounding air reabsorbs the energy within microseconds and within centimeters (at ground level) and since the air’s temperature is unchanged (conservation of energy) then the air will reemit IR energy per Wein & Stefan-Boltzmann in the wavelength range that CAN be absorbed or reabsorbed by the CO2, continuously, forever. This is HOW CO2 transports energy to higher elevations & out to space. Since the air & CO2 density is lower at higher elevations. a photon travels further going up than it does going down, hence energy is transported out to space. (in a zig-zag process of many absorbtions, at one microsecond per absorbtion, you can get a million absorbtions in a second!!)

    Another comment on saturation. When CO2 absorbs a (typical IR) photon, the molecule goes to ~900K. THEREFORE, the only way all the CO2 can be saturated is WHEN all the air is at ~900K. Otherwise the CO2 will collide with the air and cool back down to unsaturated conditions. OR looking at it in another way, IF all the CO2 DID stay saturated, then CO2 could not absorb photons, and the IR radiated photons would go directly to space faster, and hence cool down the air. We will not survive too well at ~900K. The saturation concept is a waste of energy! :)

    A side comment- the concept that CO2 “TRAPS” photons is totally absurd. There is NO way in the world, that a ~900K CO2 molecule can exist for more than a few microseconds aurrounded by 288K air molecules. Besides if CO2 traps the energy & doesn’t give it back, then how does the energy warm the air? CO2 “catches and releases” energy. It just slows the transport to space process down, which is why GHGs cause warming.

    My next question is since the air is now warmer, why doesn’t the Stefan-Boltzmann equation, that says that the energy transported out is proportional to T^4, simply transport out MORE energy faster at the warmer temperature, to return the air to the original equilibrium temperature? ie Mother Natures natural compensation process for the greenhouse effect?

    Comment by John Dodds — 13 Aug 2007 @ 4:15 PM

  280. Re #278

    Please note that I had no replies to my #278 for 4 days, and so I posted it again, in the Part 2 thread “What Angstrom didn’t know”, at #419. Good response.

    Comment by AEBanner — 14 Aug 2007 @ 6:17 AM

  281. [[ When CO2 absorbs a (typical IR) photon, the molecule goes to ~900K. THEREFORE, the only way all the CO2 can be saturated is WHEN all the air is at ~900K. Otherwise the CO2 will collide with the air and cool back down to unsaturated conditions.]]

    First of all, assigning a temperature to a single molecule is meaningless, since temperature is based on the root-mean-square velocity of a number of molecules. Second, you seem to be picturing energy disappearing when collisions take it away from CO2 molecules. Energy is conserved. The energy going into collisions is gained by the molecules in the collisions, and will therefore raise their temperature (T = M V2 / (3 R)). Since temperature will equalize for all molecules, the CO2 will also be warmer, and will radiate more. That’s how the greenhouse effect works.

    Comment by Barton Paul Levenson — 14 Aug 2007 @ 7:34 AM

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