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First published response to Lindzen and Choi

Filed under: — gavin @ 8 January 2010

The first published response to Lindzen and Choi (2009) (LC09) has just appeared “in press” (subscription) at GRL. LC09 purported to determine climate sensitivity by examining the response of radiative fluxes at the Top-of-the-Atmosphere (TOA) to ocean temperature changes in the tropics. Their conclusion was that sensitivity was very small, in obvious contradiction to the models.

In their commentary, Trenberth, Fasullo, O’Dell and Wong examine some of the assumptions that were used in LC09′s analysis. In their guest commentary, they go over some of the technical details, and conclude, somewhat forcefully, that the LC09 results were not robust and do not provide any insight into the magnitudes of climate feedbacks.

Coincidentally, there is a related paper (Chung, Yeomans and Soden) also in press (sub. req.) at GRL which also compares the feedbacks in the models to the satellite radiative flux measurements and also comes to the conclusion that the models aren’t doing that badly. They conclude that

In spite of well-known biases of tropospheric temperature and humidity in climate models, comparisons indicate that the intermodel range in the rate of clear-sky radiative damping are small despite large intermodel variability in the mean clear-sky OLR. Moreover, the model-simulated rates of radiative damping are consistent with those obtained from satellite observations and are indicative of a strong positive correlation between temperature and water vapor variations over a broad range of spatiotemporal scales.

It will take a little time to assess the issues that have been raised (and these papers are unlikely to be the last word), but it is worth making a couple of points about the process. First off, LC09 was not a nonsense paper – that is, it didn’t have completely obvious flaws that should have been caught by peer review (unlike say, McLean et al, 2009 or Douglass et al, 2008). Even if it now turns out that the analysis was not robust, it was not that the analysis was not worth trying, and the work being done to re-examine these questions is a useful contributions to the literature – even if the conclusion is that this approach to the analysis is flawed.

More generally, this episode underlines the danger in reading too much into single papers. For papers that appear to go against the mainstream (in either direction), the likelihood is that the conclusions will not stand up for long, but sometimes it takes a while for this to be clear. Research at the cutting edge – where you are pushing the limits of the data or the theory – is like that. If the answers were obvious, we wouldn’t need to do research.

Update: More commentary at DotEarth including a response from Lindzen.


141 Responses to “First published response to Lindzen and Choi”

  1. 101
    Bill DeMott says:

    Comment by Simon Rika — 10 January 2010 @ 2:58 PM

    Simon–you are just wrong in suggesting that journals should not be gate keepers. Many times I have recommended that a manuscript be rejected for this journal (x), but it would make a good paper for journal y. Every knows that journal y is more prestigious and that the quality of manuscripts received is very high, but 80% are rejected. The biggest reason for rejecting manuscripts has nothing to do with mistakes or errors. Rather, the manuscript just does not reach the level of quality and impact required to be published in journal y. These lower quality but “valid” studies can be published in lower tier journals.

  2. 102
    Bill DeMott says:

    Sorry about the confusion in my comment above. My intent was to say that a manuscript rejected by a more prestigious journal can make a good paper for a lower tier and often more specialized journal. Every time a scientist starts writing a manuscript he or she needs to decide the target journal. This is in part a matter of strategy. “Should I aim for the more prestigious journal or just be satisfied with the less competitive journal?”

  3. 103
    Joel Shore says:

    #98 Jiminmpls:

    Your statement about it being “*significantly* colder than normal” may be true for the southeast & south central U.S., but I don’t think it is true in the Northeast. At least here in Rochester, NY, I would say that the departure is not particularly dramatic. Yes, it’s certainly been colder than average for the last couple of weeks, but not dramatically so. In fact, I would venture to say that a year when we did not have a period this cold sometime during the winter would be anomalous.

  4. 104
    Timothy Chase says:

    Jason Miller wrote in 100:

    If anyone else knows of some good papers not behind pay walls please let me know. I watched 22 inches of snow melt to a few inches over a cold (just above freezing), wet Christmas day last month and I am curious about any acceleration of the glaciers and ice packs that rain can cause.

    I would recommend doing a search in http://scholar.google.com for glaciers rain acceleration modeling pdf and you will probably find papers that fit the bill. Maybe not the ones that you are specifically looking for, but…

    One paper that seems like it may address a few of your questions is the following:

    A physically based approach to compute melt involves the assessment of the energy fluxes to and from the surface. At a surface temperature of 0C, any surplus of energy at the surface-air interface is assumed to be used immediately for melting. The energy balance in terms of its components is expressed as:

    QN+QH+QL+QG+QR+QM = 0 (1)

    where QN is net radiation, QH is the sensible heat flux, QL is the latent heat flux (QH and QL are referred to as turbulent heat fluxes), QG is the ground heat flux, i.e., the change in heat of a vertical column from the surface to the depth at which vertical heat transfer is negligible, QR is the sensible heat flux supplied by rain and QM is the energy consumed by melt. As commonly defined in glaciology, a positive sign indicates an energy gain to the surface, a negative sign an energy loss. Melt rates, M are then computed from the available energy by:

    M = QM/(ρw*Lf) (2)

    where ρw denotes the density of water and Lf the latent heat of fusion. Energy-balance models fall into two categories: point studies and distributed models.

    pg. 366, Regine Hock(2005) Glacier melt: a review of processes and their modelling, Progress in Physical Geography 29, 3, pp. 362–391, (60 citations)

    Hope this helps…

  5. 105
    Timothy Chase says:

    PS RE Jason Miller

    One search term I have often found useful at times is “review”. At least in evolutionary biology it isn’t uncommon for a review to contain references to over a hundred papers, and typically a good review will be just that — a review of the current state of investigation into its subject, fairly in depth yet written for the nonspecial-ist. If you are looking for answers to some fairly basic questions, getting too many results but each too narrow in their focus to deal with those questions, “review” may get you what you want.

  6. 106
    Doug Bostrom says:

    Joel Shore says: 10 January 2010 at 9:55 PM

    #98 Jiminmpls:

    “Your statement about it being “*significantly* colder than normal” may be true for the southeast & south central U.S., but I don’t think it is true in the Northeast.”

    Meanwhile here in Western Washington we’ve been setting some record highs the past few days. Last month, record lows. Global warming, disproved and proved again, within a month, uh-huh. Watt’s up with that?

  7. 107
    John Mashey says:

    Personally, I think some science publishing has not caught up with the Internet.

    1) “In print” in a scholarly journal used to have a specific meaning, and there were fairly long lags from printing, to getting responses, and printing them.

    2) I’m really not exactly sure what “in print” really means these the days.
    After all, a journal issue can easily contain articles subjected to ferocious review, to those subjected to none (G&T for example, seemingly). This is independent of whether something is read on-line or actually received in a bound journal.

    3) While this would certainly take work, I would really wish that journals:

    a) Do whatever they do now, clearly labeling content some way w.r.t. the leve lof review. Some are certain clear about this, others not.

    b) But this business of letters/articles, etc seems unnecessarily broken in the Internet age. I know it’s more work, but I’d sure love to see a a blog thread provided for each such article, open for a while following publication, and tightly moderated, to encourage substantive comments by experts.

    c) As it is, if a non-expert wants to ask:

    “What was the reaction to this paper?” it can take a lot of work to find:
    “This paper was refuted fairly quickly.” because that fact may well be scattered all over the place. Immediate, simple comments like “reference XYZ wasn’t mentioned and comes to opposite results” ought to be easy.

    It might *never* be refuted by a real paper, if it’s not worth the bother. There is no simple way to go from a paper directly to proposed refutations, although you can look up citations, and see what they say, if you have access to those journals. I’ve sometimes tried this. It wastes a lot of time.

    Anyway, it would be awfully nice if credible quick feedback could easily be directly associated with an article.

  8. 108
    Ray Ladbury says:

    Andrew@88, I’ve just started to look at Information Geometry. I can already see that it would be quite powerful. However, I work in a rather applied field–I got in trouble with one reviewer for even using AIC in a recent paper. He said that it must be an obscure technique because he’d never heard of it! I suggested an alternative explanation and the paper was published.

    I suspect I would be lynched if I tried to bring non-Euclidian geometry into the mix.

  9. 109
    Simon Rika says:

    @Andrew #97

    I didn’t mean they shouldn’t catch errors. I meant they should not use such errors to refuse to publish unless they are clearly intentional. An intentional error would be one the authors refuse to correct or explain why their way is better/correct. But if they do have an explanation why their way should be considered correct, then if they still want it published, they should be able to be published with the notification that the reviewers have raised concerns, and the authors have addressed them.

    I know I’m probably just confusing you even more – I guess I can’t explain myself properly, and this is off topic. Sorry.

    @Bill DeMott #101

    I’m not sure what you described is much different from what I proposed, except perhaps in wording. Being published in a different journal is not the same as being refused publication, to me anyway. I’m simply saying if the journal wants to publish it, and the authors address any issues raised by the reviewers, then they have done their job, and it is up to other scientists to refute or ignore it. I am not saying in this particular case the reviewers did a good job of raising these issues or the authors addressed them.

    I just noticed that some people seemed to be saying that even if the paper has raised valid questions, if there were any errors it should be refused publication, regardless of any benefit it might have.

    In this particular case, I got the impression that the journal in question was one of those lower tier journals that publishes just about anything. Was I wrong in that impression?

  10. 110
    Completely Fed Up says:

    Simon: “I didn’t mean they shouldn’t catch errors. I meant they should not use such errors to refuse to publish unless they are clearly intentional.”

    Or if the errors are bad enough that persuing the paper requires a new paper WITHOUT the errors to allow at least some sort of progress.

    If there are too many errors, you can’t use the paper at all. E.g. if you were a 17 year old high school student writing a paper on string theory, there’s likely to be a LOT of unintentional errors and anyone wanting to use that paper for anything will have to repeat a lot of work finding out what is an error and what is arguable.

  11. 111
    Ray Ladbury says:

    John Mashey, I think that part of the problem IS the Internet age. After all, substandard work has always found its way into obscure journals. In the past, it would moulder there and generate the lack of attention it so richly deserves. Now, there is no journal so obscure (the Quarterly Journal of the Hungarian Meteorological Service, ferchrissake!?!) that a substandard paper can’t go viral (or virial in Miskolczi’s case;-) ) among the gullible.

    In the case of LC’09, they did at least publish in a mainstream journal, available to the community. I just wish the peer review could have been better so that it could have been either definitively rejected, or the authors could have taken their best shot and stood or fell (most likely, fell) on the merits of their argument.

    You have to admit that the process plays out more efficiently in the peer-reviewed literature than in the blogosphere.

  12. 112
    Jiminmpls says:

    #106 Doug, Gavin and Hank,

    Since when are the GRL and NSIDC “pop” news sources? If you don’t recognize this cold as an extreme weather event, you’re not paying attention. Occassional nights that dip below freezing are not unusual in southern FL. A week long freeze is pretty much unprecedented.

    So, what is causing this extreme cold weather event?

    From the NDISC..

    “The phase of the AO is described in terms of an index value. In December 2009 the AO index value was -3.41, the most negative value since at least 1950, according to data from the NOAA Climate Prediction Center…….The negative and positive phases of the AO set up opposing temperature patterns. With the AO in its negative phase this season, the Arctic is warmer than average, while parts of the middle latitudes are colder than normal. The phase of the AO also affects patterns of precipitation, especially over Europe. ”

    From http://www.agu.org/pubs/crossref/2008/2008GL035607.shtml

    “Recent radical shifts of atmospheric circulations and rapid changes in Arctic climate system”

    *Extreme* negative phase and *radical shifts* in the AO don’t sound like business as usual to me.

    And no, the climate models don’t predict this change in the AO. They didn’t predict the rapid decline in Arctic sea ice observed since 2005, either. And warm temps in Washington State are consistent with the Dipole pattern.

    References
    Francis, J.A., W. Chan, D.J. Leathers, J.R. Miller, and D.E. Veron, 2009, “Winter Northern Hemisphere weather patterns remember summer Arctic sea-ice extent”, Geophysical Research Letters, 36, L07503, doi:10.1029/2009GL037274.

    Honda, M., J. Inoue, and S. Yamane, 2009. Influence of low Arctic sea – ice minima on anomalously cold Eurasian winters, Geophys. Res. Lett., 36, L08707, doi:10.1029/2008GL037079.

    Overland, J. E., M. Wang, and S. Salo, 2008: The recent Arctic warm period. Tellus, 60A, 589.597.

    Richter-Menge, J., and J.E. Overland, Eds., 2009: Arctic Report Card 2009, http://www.arctic.noaa.gov/reportcard.

    Simmonds, I., and K. Keay (2009), Extraordinary September Arctic sea ice reductions and their relationships with storm behavior over 1979.2008, Geophys. Res. Lett., 36, L19715, doi:10.1029/2009GL039810.

    Wu, B., J. Wang, and J. E. Walsh, 2006: Dipole anomaly in the winter Arctic atmosphere and its association with sea ice motion. J. Climate, 19, 210-225.

    Zhang, X., A. Sorteberg, J. Zhang, R. Gerdes, and J. C. Comiso (2008), Recent radical shifts of atmospheric circulations and rapid changes in Arctic climate system, Geophys. Res. Lett., 35, L22701, doi:10.1029/2008GL035607.

  13. 113
    Doug Bostrom says:

    Comment by Jiminmpls — 12 January 2010 @ 7:43 AM

    Jim, are we disagreeing? I don’t think so.

    Absolutely, it’s an extreme weather event; if you’ve got water pipes installed in your attic because that seemed ok during the short period Florida has been under development and you now have a volunteer sprinkler system dripping through the ceiling, you’re going to damply stand there saying “What the hell is all this talk about warming, for Pete’s sake?”

    There is no plan for when and where heat is going to be delivered. As I mentioned, we had a string of record cold temperatures set here in Western Washington last month, this month we’ve had some record highs. The only solid conclusion I can draw from this scanty local data is that for any location we choose we’ll find our archive of measurements to be pretty brief. Our detailed weather history for any location is paltry.

    Now widen the scope, take a snapshot of the entire globe and weather effects largely vanish. Then we see that whatever the situation in any particular bit of the world, such as your wet Barcalounger, the overall temperature signal is not so different from what it was prior to the onset of the cold snap in Florida and NE Europe. From this viewpoint we can get a datapoint that’s useful when thinking about climate.

    Keep the same global viewpoint, take snapshots through time and only then can we draw any inferences about the overall direction of Earth’s climate.

    Not so hard, really, but when you’ve got your phone in one hand calling the insurance adjuster and the other gripping the hose of a shopvac sucking water out of your carpet the big picture is not going to be uppermost in mind.

  14. 114
    John Mashey says:

    re: 111
    ray: I wasn’t saying Internet made for goodness.
    I would much rather not have commentary spread all over the blogosphere. I have long been irritated at the assymmetry between between articles and letter in many places. I simply observe that it would be value-add for a journal to figure out how to use the Internet to collect well-moderated material “near” an article.

    Journals already publish mixes of material, with combinations of:

    a) Time-lag
    b) Size
    c) “Credibility” (of peer-review, knowledgable editorial board, review, etc).

    I just think we ought to think about how to use the Internet more efficiently to promote good work. Personally, I think that publishing something, only to have serious refutations placed next to my article within a few days, might make me think harder.

    Some of what goes on now reminds me too much of MS Fnd in a Lbry. :-)

  15. 115
    JBowers says:

    To be fair to Latif, he has hit back at the distortion in the Guardian:
    http://deepclimate.org/2010/01/11/mojib-latif-slams-daily-mail/
    http://www.guardian.co.uk/environment/2010/jan/11/climate-change-global-warming-mojib-latif

    More here from earlier distortions:
    http://deepclimate.org/2009/10/02/an-email-exchange-with-mojib-latif/
    http://deepclimate.org/2009/10/02/anatomy-of-a-lie-how-morano-and-gunter-spun-latif-out-of-contro/

    WUWT ran with the story as well, and offered Latif a guest post to explain his position which I see as an insulting gesture given it’s the Mail’s reporter, David Rose, who should be doing the explaining.

  16. 116
    Muhammad Bear says:

    At 51 Gavin said “The Planck long wave emission (sigma&T^4) is the dominant negative feedback. Everything else is just modifying that.”

    Infrared radiation accounts for about 42 % of heat removed from the surface whereas about 48 % percent of surface heat removed is in the form of latent energy. Would this not make surface water evaporation the dominant negative feedback?

    [Response: There's no evaporation to space. - gavin]

    Of course there are both positive and negative feedbacks but the climate system has to be dominated by negative feedbacks. Turn off the sun and it would cool very quickly. Any engineer will tell you a system dominated by positive feedbacks is unstable.

  17. 117
    Muhammad Bear says:

    At 116 “There’s no evaporation to space. – gavin”

    Agreed. My understanding is that the process (as far as latent heat is concerned) is through convection and the heat is transferred to the troposphere once the water vapour condenses and the latent energy is released in the form of sensible heat. I wasn’t suggesting that water vapour convects to space.

    My point was merely that more heat is taken away from the surface through evaporation than through electromagnetic radiation.

    [Response: What happens at the surface is only a part of the change that determines the planetary response. More importantly, you need to think about the energy fluxes at the top of the atmosphere - which are radiative, and that is why the sigma*T^4 response is the dominant negative feedback. - gavin]

  18. 118

    Muhammad Bear,

    You have positive feedbacks confused with diverging feedbacks.

  19. 119

    MB: My point was merely that more heat is taken away from the surface through evaporation than through electromagnetic radiation.

    BPL: Your point is wrong. The Earth’s surface radiates about 389 watts per square meter on mean global annual average, compared to losing 80 watts per square meter to latent heat and 17 to sensible heat. That means 80% radiation, 16% evaporation.

  20. 120
    Completely Fed Up says:

    Gavin’s inline implies a different idea as to what “negative feedback” could mean.

    Not what I’d call a feedback, since it makes the questioning of negative feedbacks in climate models somewhat silly: it makes temperature itself a negative feedback.

  21. 121
    Ray Ladbury says:

    CFU,
    It is clearly a feedback, as the energy loss increases with increasing temperature.

  22. 122
    Muhammad Bear says:

    Okay. I was possibly making a really bad point.

    I was just limiting the feedback analysis to the response to surface insolation; i.e. incoming short wave radiation tries to heat the surface and IR and convection are negative feedbacks to this process.

    BPL and Gavin are right as I was ignoring the effects of longwave radiation and the GH. I was analysing this as feedbacks later in the process. I probably misunderstood Gavin’s initial point as I thought he was just referring to the Earth’s surface as the blackbody.

  23. 123
    Ray Ladbury says:

    Muhammad Bear,
    It’s easy to get mixed up, especially with slightly different usages of the term “feedback”.

  24. 124
    Completely Fed Up says:

    And the other problem: lots of the simplifying assumptions of figuring out temperatures depends on a local equilibrium and no spectral response.

    Yet GG activities require knowing when and how they are both broken.

  25. 125
    Completely Fed Up says:

    Ray, 121, however, since it’s what we’re trying to measure, making temperature the feedback is more than a little weird.

  26. 126
    Muhammad Bear says:

    BPL, 119: Your point is wrong.

    I have just looked at this again. Actually, my point was correct (in intent) but very badly expressed. I should have said that most of the energy is removed from the Earth’s surface through the convection of sensible heat and latent energy compared with energy removed through NET longwave radiation.

    When viewed in terms of upward longwave released less downward longwave received less energy is released through radiative transfer. I just wanted to clarify what I meant.

  27. 127
    Ray Ladbury says:

    CFU, It is not that temperature is the feedback, but rather that the feedback (thermal radiation) scales with temperature. What is more, there is nothing that unusual about this. Most other feedbacks–e.g. water vapor, albedo from ice/snow, CO2 from melting permafrost or clathrates, etc.–also scale with temperature, although not as directly.

  28. 128
    Hank Roberts says:

    > When viewed in terms of upward longwave released less
    > downward longwave received less energy is released
    > through radiative transfer. I just wanted to clarify what I meant.

    You might want to try one more time, with a few more short words.
    “Viewed in terms of” is about as vague as it gets.

  29. 129
    Completely Fed Up says:

    Ray, feedbacks (especially negative ones) are usually counted as, for example, cloud cover. Or the brightening of land by desertification.

    I’ve not heard temperature characterised as one before.

  30. 130
    Timothy Chase says:

    Muhammad Bear wrote in 117:

    My point was merely that more heat is taken away from the surface through evaporation than through electromagnetic radiation.

    Barton Paul Levenson wrote in 119:

    Your point is wrong. The Earth’s surface radiates about 389 watts per square meter on mean global annual average, compared to losing 80 watts per square meter to latent heat and 17 to sensible heat. That means 80% radiation, 16% evaporation.

    Muhammad Bear wrote in 126:

    I have just looked at this again. Actually, my point was correct (in intent) but very badly expressed. I should have said that most of the energy is removed from the Earth’s surface through the convection of sensible heat and latent energy compared with energy removed through NET longwave radiation.

    When viewed in terms of upward longwave released less downward longwave received less energy is released through radiative transfer. I just wanted to clarify what I meant.

    You are making some good points. However in discussions it is oftentimes easier to focus on points of disagreement rather than agreement. In the recent thread Plass and Surface Budget Fallacy they discuss two of the energy budgets — or “balances” if you think of a “balance” in terms of what you have left over after all of the “accounting”.

    By the principle of the conservation of energy, if the rate at which energy enters a given volume is greater than the rate at which it exits the volume, then the net rate at which it enters the volume is positive and the amount of energy in that volume will increase over time. The same thing applies to mass, momentum and other conserved quantities. And the same thing applies to thermal energy if one includes the generation of thermal energy due to a dissipative process in the term for thermal energy entering the volume.

    You can certainly consider energy in terms of the surface budget, but you may also consider it in terms of the ocean budget, atmospheric budget, land budget, tropics budget and so on. At the same time, the fundamental energy budget is that which exists for the climate system as a whole — and this is what Gavin was pointing to when he inlined in 117:

    What happens at the surface is only a part of the change that determines the planetary response. More importantly, you need to think about the energy fluxes at the top of the atmosphere – which are radiative, and that is why the sigma*T^4 response is the dominant negative feedback.

    Gavin’s point is of fundamental importance — the energy budget of the climate system as a whole is what lies at the center of the greenhouse effect that raises the temperature of the climate system above the effective radiating temperature of the climate system — that is the temperature that the planet would have in the absence of the atmosphere. Effectively, the top of the atmosphere is the surface than bounds that volume, and thus what crosses that surface, entering or leaving the volume, is of fundamental importance to the climate system as a whole. But at the same time it helps to be able to think in terms of the other budgets. And we I think that in our discussions we sometimes lose sight of the latter when focusing on the former.
    *
    Mohammad Bear wrote in 116:

    Of course there are both positive and negative feedbacks but the climate system has to be dominated by negative feedbacks. Turn off the sun and it would cool very quickly. Any engineer will tell you a system dominated by positive feedbacks is unstable.

    I am not exactly sure how engineering applies the term “positive feedback,” and it is possible that there is some important difference. However, as “feedback” is applied in climatology, it is thought of principally in relation to “radiative forcing.” There is the forcing that raises the surface temperature by a certain number of degrees. Increased solar radiation, for example. Then there is the response to this initial forcing. The rise in temperature — which in the absence of an atmosphere would simply result in an increase it the rate at which thermal radiation is emitted by the surface — according to the sigma*T^4 response that Gavin mentioned — where sigma refers to the emissivity of the surface and the T^4 comes from Planck’s law of blackbody radiation.

    But then there is evaporation, which removes heat from the surface but moves heat into the atmosphere. In terms of the fundamental energy budget this isn’t yet what would be considered a “feedback” as it has neither increased nor reduced the net rate at which energy enters or leaves the climate system. However, when the water evaporates from the surface this results in increased water vapor — and water vapor is a greenhouse gas.

    This increases the opacity of the atmosphere to thermal radiation. This will reduce the rate at which energy escapes the climate system, but energy will continue to enter the climate system at the same rate as before. Therefore the amount of energy in the climate system will increase. And likewise the amount of thermal energy in the climate system will increase.

    Now this will not mean any sort of runaway global warming where the temperature increases without limit. Such a thing is clearly impossible. Nor will it mean runaway global warming in the sense that applied to the evolution of Venus. In fact it won’t mean runaway global warming in any sense at all. However, it does mean that the surface has to warm further if the climate system is to emit thermal radiation at a rate that is equal to the rate at which thermal radiation is entering the system.

    As such the temperature response is greater than that which would result from the forcing (in this case, increased solar radiation) alone. This is why we refer to the feedback as a “positive” feedback. In contrast, a “negative” feedback would result in an overall increase in temperature that is smaller than that which would come from the initial forcing.
    *
    Now you had stated, “Any engineer will tell you a system dominated by positive feedbacks is unstable.”

    However, if by “unstable” you are refering to a runaway effect, this isn’t the case.

    Of course if increased water vapor results in an increase in temperature this will result in more water vapor that will result in a further increase in temperature, but on earth at least this generally won’t result in a runaway effect. Not since each additional increase in water vapor results in a smaller increase in temperature than the previous increase in temperature. Positive feedback is limited just as a geometric sum is limited when each successive term is smaller than the term before it. Thus for example, (1/2)^0+(1/2)^1+(1/2)^2+(1/2)^3+… (1/2)^(n-1)+(1/2)^n is less than 2 so long as n is finite and goes only to 2 when n approaches infinity.

    However, all this talk in terms of forcings and feedbacks is immaterial as far as climate models themselves are concerned. They don’t work in terms of forcings and feedbacks. They are based upon the principles of physics. Generally speaking, talk in terms of “forcings” and “feedbacks” is strictly for our convenience — when we analyze how the climate system increases in response to an increase in the rate at which energy enters the system, a reduction in the rate at which it escapes, etc..

  31. 131
    Ray Ladbury says:

    CFU, you didn’t read what I wrote. TEMPERATURE is NOT the negative feedback. Rather the negative feedback SCALES WITH TEMPERATURE to the 4th power. This is a different matter. Water vapor also scales with temperature pretty directly. And most other feedbacks have some sort of scaling with temperature.

  32. 132
    Timothy Chase says:

    Muhammad Bear wrote in 126:

    When viewed in terms of upward longwave released less downward longwave received less energy is released through radiative transfer. I just wanted to clarify what I meant.

    Hank Roberts wrote in 128:

    You might want to try one more time, with a few more short words. “Viewed in terms of” is about as vague as it gets.

    Oh dear!

    I rather liked the expression, myself. “Viewed in terms of”, “from the perspective of”, “in this context” and so on. But I suppose that’s my dialectics again. Don’t blame Chris Matthew Sciabarra — it really was a problem well before I even ran into him. And of course he would tell you that the blame ultimately rests with Aristotle. But I suppose all of that is really beside the point…

    In either case, you might find the last sentence of the preceding paragraph a bit clearer — it was expressing the same idea.

    There Muhammad Bear had stated:

    I should have said that most of the energy is removed from the Earth’s surface through the convection of sensible heat and latent energy compared with energy removed through NET longwave radiation.

    Upward longwave released (upwelling longwave radiation) less (minus) downward longwave received (downwelling longwave radiation) is net longwave radiation. And the rate at which net longwave radiation carries thermal energy away from the surface is smaller than the rate at which thermal energy is carried away — from the surface — through evaporation.

    (But of course, for all intents and purposes, the only way thermal energy will ultimately leave the climate system itself is through thermal radiation. And from this perspective (that is, viewed in the context of the energy budget of the climate system as a whole) evaporation carrying away latent energy is simply moving thermal energy around within the climate system but never actually getting it out — except insofar as it facilitates the loss of thermal energy through radiation at higher altitudes.)

  33. 133
    RB says:

    Muhammad Bear: “Any engineer will tell you a system dominated by positive feedbacks is unstable.”

    I am an engineer and can say that Muhammad Bear is an incompetent engineer. Specifically, for a linear feedback model with forward gain G and feedback gain H, with an input transfer to output transfer function of
    G/(1+GH) if -1<GH<0, there is amplification without a runaway effect.

  34. 134
    Timothy Chase says:

    Re RB 133

    Is “unstable” synonymous with being prone to “runaway effects,” or could he have simply been referring to the amplification itself? In either case and as you would no doubt point out — amplification is not a problem. Unbounded amplification — runaway effects — that would be a problem.

  35. 135
    Completely Fed Up says:

    “(But of course, for all intents and purposes, the only way thermal energy will ultimately leave the climate system itself is through thermal radiation)”

    An irrelevant distinction: the only way energy will leave the climate system is through radiation.

    It’s complicated enough as it is.

  36. 136
    Completely Fed Up says:

    I wonder if those who do not understand feedbacks can explain how lagging on a hot water tank can work.

    After all, the lagging produces no heat of its own.

  37. 137
    RB says:

    I apologize for the tone in(#133) , that was uncalled for. Since for BIBO (bounded input bounded output) stability, we need to avoid GH= -1 (or a phase of 180 degrees at unity gain), when designing circuits, we shoot for typically ensuring 60 degree phase margin (i.e. a phase not exceeding 120 degrees or 60 degrees below 180). This results in some overshoot but the oscillatory phenomena for transient changes is damped.

  38. 138
  39. 139

    MB, your point is still wrong. Why do you count longwave radiation as NET but convection and conduction as GROSS? The inputs are:

    161.2 watts/square meter sunlight
    324.8 watts/square meter IR from the atmosphere

    The outputs are:

    17 watts/square meter sensible heat
    80 watts/square meter latent heat
    389 watts/square meter longwave radiation

    You are taking two streams from the output side and comparing them to the net from one input stream and one output stream. Why?

  40. 140

    I, too, am curious about the effects of rain on the glaciers and if more rain led to more and quicker melting.

  41. 141

    I think this is a great closing comment : “…the episode underlines the danger in reading too much into single papers…go against the mainstream (in either direction) …. conclusions will not stand up … takes a while for this to be clear. Research at the cutting edge pushing the limits of the data or the theory if the answers were obvious, we wouldn’t need to do research.”

    I agree with this …and if the science were settled there also would be no debate on the science, only on the policy solution.

    The issue is – this really is a policy matter … as discussed at http://climate-check.blogspot.com/. Magritte painting of a pipe (“Ceci n’est pas une pipe”) is a painting, not a an actual pipe, and how well this fits your idea of a pipe depends on your interpretation – filtered through ones lens or world view of a pipe not looking through the eyes of the painter.

    IPCCs probabilities are not statistical tests of scientific hypotheses about whether a model describes an outcome (… I say that the IPCC assigned numerical (Delphi) probabilities are truly nonsense). The policy issue is highly leveraged on the 100 year model outputs and claims of warming 1.5-4.5 oC or whatever it is these days. The model outputs are not capable of verification or falsification by testing a hypothesis and the model projection is 100 years out of sample. The models can be tested in sample, i.e., in a backcast. Determination of heat trapping capability of GHG “forcings” is science … applying these in a “nonverifiable” out of sample (100 years) projecting (not a “prediction”) a temperature increase is not science … it is computer code.

    And we are still at early stages of understandings on other important forcings and feedback interactions. Over some time (?) the models projections will be tested – I imagine over the next 5 years the models will be improved and expanded to include important non manmade forcings and tested allowing better confidence. As things stand now the “way” the models are being used and the results communicated result in a lot of criticism and questions on the uncertainties as discussed on this RealClimate page.

    The different theories or models will indeed play out as a “rugby scrum” over some time (a few years?) until one or a group of models are more or less accepted. Then everyone including the public … and even the politicians … will understand with greater confidence. It is not like solving Poincare’s conjecture – mathematical proof starting from basic premises. The models now are not hypotheses but conjectures – unproven hypotheses although underpinned by basic physical science.

    Policy models are not required to be “complete” or “correct” descriptions (models) of actual working systems. They simply have to be deemed acceptable for making policy decisions. As in Douglas Elmendorf’s macroeconomic models to look at stimulus and jobs.

    Peseran (1996, 2004) defines three criteria for evaluation of policy models – relevance, consistency and adequacy. Relevance – does the model meet its required purpose? Consistency – what else is known that may be useful and is it being used. Adequacy – the usual statistical measures of goodness of fit. Consistency and adequacy are important when building a model. But a generalized form of relevance is the most important thing for evaluation of the model. Dagum (1989) said “knowledge is of value only when it is put to use,” and Marshak said “knowledge is useful it helps to make the best decisions.” Also, Keynes said about Alfred Marshall, “Marshall arrives early at the point of view that the bare bones of economic theory is not worth much in themselves and do not carry one directly to any useful practical conclusions. The whole point lies in applying them to the interpretation of current economic life.”


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