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Climate Sensitivity Estimates: Heading Down, Way Down? (Richard Lindzen’s New Paper)

By Chip Knappenberger -- August 26, 2009

MIT climate scientists Richard Lindzen and collaborator Yong-Sang Choi soon-to-be published paper (Geophysical Research Letters, American Geophysical Union) pegs the earth’s “climate sensitivity”—the degree the earth’s temperature responds to various forces of change—at a value that is about six times less than the “best estimate” put forth by the Intergovernmental Panel on Climate Change (IPCC). The smaller the climate sensitivity, the less the impact that rising carbon dioxide levels will have on the earth’s climate. The less the impact that CO2 emissions will have on the earth’s climate, the less the “problem” and ability to reverse the “problem.”

Lindzen and Choi’s findings should come as a solace to those folks who are alarmed about future climate and as a bulwark to those folks fighting to limit Congresses negative impact on U.S. energy supplies and our economy. Indeed, climate sensitivity to GHGs is the multi-billion dollar question in climate science. If climate sensitivity is low, then the earth’s temperature doesn’t react very much to variations in processes which impact it—such things as solar variations, volcanic eruptions, cloudcover fluctuations or changes in the concentration of greenhouse gases.

If, on the other hand, the climate sensitivity is high, then changes in the climate drivers can lead to large changes of the earth’s average temperatures. Another way to think of it is that the lower the climate sensitivity, the more stable the earth’s climate.

Climate sensitivity is hotly debated because we have don’t have a good enough handle on the magnitude of the earth’s past temperature changes and an even worse understanding on the magnitude of the variation of climate drivers. So while theoretically evaluating the climate sensitivity is as easy as dividing the temperature change by the forcing change, in practice, a poor understanding of both the numerator and the denominator have made it virtually impossible to pin down.

IPCC Estimatation and the ‘Wild Card’ of Clouds

In its 2007 Fourth Assessment Report (AR4), the IPCC claims that the climate sensitivity to a doubling of atmospheric greenhouse gas concentrations likely falls in the range of 2.0°C to 4.5°C. This is based on a combination of studies, some making determinations based on historical data, others basing their results on climate model output.

But again, the problem with the former is an observational record that is not accurate enough to make a reliable calculation; the problem with the latter is that the physical processes simulated by climate models are limited both by our less-than-perfect understanding of these processes as well as by modern-day computation power (which limits the temporal and spatial resolution of the climate simulation).

One area where climate models are particularly weak is in their ability to accurately simulate clouds and cloud variations. And, as you probably could have guessed, clouds and cloud variations play a pivotal role in establishing the earth’s average temperature.

There is a fast-growing evidence base that clouds respond to changes in greenhouse gas concentrations quite differently than the climate models predict that they should. Instead of acting to enhance the warming produced by increases in the earth’s greenhouse gas concentrations, it seems as if clouds may, in fact, act to suppress the rate of greenhouse gas-induced temperature rise.

New Findings

The latest findings to this effect by Lindzen and Choi add to the work that Roy Spencer and several other researchers have been doing for years in this arena. Instead of a climate sensitivity lying within the IPCC’s range of 2.0° to 4.5°C, Lindzen and Choi report it to be about 0.5°C—six times less than the IPCC’s “best estimate” of 3.0°C.

Lindzen and Choi make their determination by examining radiation data measured by instruments carried by satellites orbiting above the earth’s atmosphere and comparing the variation of incoming and outgoing radiation with the variations in the earth’s tropical ocean temperatures. Climate models seem to predict that when the ocean temperature increases, less radiation leaves the earth to space, which leads to additional warming—a positive feedback.

However, actual observations seem to show that warmer oceans results in more radiation lost to space, which acts to reverse the warming—in other words, a negative feedback. Changes in cloudcover are one possible mechanism involved. The data presented by Lindzen and Choi are shown in Figure 1. The red box surrounds the data from the observations and shows a positive relationship between sea surface temperature changes and the amount of radiation lost to space, while the climate models (the other 11 boxes in Figure 1) show the opposite—radiation lost to space declines as ocean temperatures rise.


Figure 1. The observed relationship between ocean temperature changes (x-axis) and radiation flux to space (y-axis) is contained in the graph with the red box around it. The other graphs depict the relationship as predicted by 11 different climate models (adapted from Lindzen and Choi, 2009).

This is a major paper. And as with most findings with serious repercussions to our scientific understanding, it will doubtlessly be gone over with a fine-toothed comb and subject to various challenges. It is too early to tell whether Lindzen and Choi’s findings will prove to be the end-all be-all in this debate. There are a few issues concerning the quality of the satellite data, how well the results from tropics represent the entire world, the impact that the eruption of Mt Pinatubo may have imparted on the results, and perhaps a couple of other details. But, even if the resolution of these issues bumps up Lindzen and Choi’s original determination of the climate sensitivity a bit, there is still a long way to go before it comes close to the IPCC’s “best estimate” of 3.0°C.

Unsettled Science … and ‘Skeptic’ Momentum

Lindzen and Choi findings could fundamentally shift the climate debate, especially when they are considered along side of the growing number of scientific publications (see references below) that have reached the same general conclusion—that the climate model determinations of the earth’s climate sensitivity are too large.

No longer can low sensitivity estimates be brushed away as some silly notion dreamed up by climate change naysayers; instead, they must be taken seriously, especially in light of the earth’s recent recalcitrance to warm at the rate projected by climate models for the early 21st century.

These results should factor prominently in any discussions aimed at trying to limit projected future warming by reducing greenhouse gas emissions as they make a strong case that such actions would be a waste of time and effort.


Chylek, P., and U. Lohmann (2008), Aerosol radiative forcing and climate sensitivity deduced from the Last Glacial Maximum to Holocene transition. Geophysical Research Letters, 35, L04804, doi:10.1029/2007GL032759.

Chylek, P., U. Lohmann, M. Dubey, M. Mishchenko, R. Kahn, and A. Ohmura (2007), Limits on climate sensitivity derived from recent satellite and surface observations, Journal of Geophysical Research, 112, D24S04, doi:10.1029/2007JD008740.

Douglass, D. H., and R. S. Knox (2005), Climate forcing by the volcanic eruption of Mount Pinatubo, Geophysical Research Letters, 32, L05710, doi:10.1029/2004GL022119.

Idso, S. B., (1998) CO2-induced global warming: a skeptic’s view of potential climate change, Climate Research, 10, 69-82.

Lindzen, R. S., and Y-S. (2009) On the determination of climate feedbacks from ERBE data, Geophysical Research Letters, in press.

Scafetta, N., and B. J. West (2007), Phenomenological reconstructions of the solar signature in the Northern Hemisphere surface temperature records since 1600, Journal of Geophysical Research, 112, D24S03, doi:10.1029/2007JD008437.

Schwartz, S. E., (2007) Heat capacity, time constant, and sensitivity of Earth’s climate system. Journal of Geophysical Research, 112, D24S05, doi:10.1029/2007JD008746

Schwartz, S. E., (2008) Reply to comments by G. Foster et al., R. Knutti et al., and N. Scafetta on “Heat capacity, time constant, and sensitivity of Earth’s climate system”. Schwartz S. E. Journal of Geophysical Research, 113, D15105 (2008), doi:10.1029/2008JD009872.

Spencer, R. W., and W. D. Braswell (2008), Potential biases in feedback diagnosis from observations data: a simple model demonstration, Journal of Climate, 21, 5624-5628.

Wyant, M. C., M., Khairoutdinov, and C. S. Bretherton (2006), Climate sensitivity and cloud response of a GCM with a superparameterization. Geophysical Research Letters, 33, L06714


  1. Andrew  

    Glad to see you finally highlight this one Chip. It may well prove to be a very important paper on this issue. I have conducted an examination of the literature that relates to this topic and in fact believe that the result of considering all the various findings is probably actually very close to Lindzen’s estimate:


    RC hasn’t “discredited” it yet, so it should be interesting to see whether they ever do, and if and when that happens, what they say.


  2. C3H Editor  


    What climate sensitivity does the MAGICC model assume?

    If one can change the sensitivity variable in the MAGICC model, it would be interesting to see an update of your excellent postings on the Waxman-Markey impact on global temperatures with the sensitivity dialed down to 0.5°C. Having a new C.K. impact scenario(s) based on the latest science would be very helpful in the upcoming Senate debate and in blogland, IMO.

    C3H Editor


  3. Andrew  

    C3H-I think that sensitivity is an adjustable parameter for MAGICC, but the default is something like the IPCC’s “central estimate” which is something like two or three degrees Celsius per CO2 doubling.


  4. cknappenberger  


    Yes, the climate sensitivity parameter in MAGICC is adjustable. I used the default value, which is 3C.

    If I set it equal to Lindzen’s 0.5C it would lower all my estimates of W-M’s climate impact by about 6 times.

    But, six times less than virtually nothing is still, well, virtually nothing!



  5. C3H Editor  

    Yep, I actually realized that the impact would be 6 times less. But if I write that in a post with no link to an impact study done by a climate scientist using a climate model, my post will be one-sixth as effective – okay, more like zero.

    Since the media, the public and politicians seem enamored with climate model results, a new model scenario using the latest science would help in countering the ludicrous “model predictions” that seem to be a daily occurrence. Having an expert produce a sane climate model result is a refreshing change and needed content. Plus, it gives me a new Master Resource link to constantly use in my postings :-). Last week, I again linked to your original “impact” article with this posting and new chart:


    I hope you find the time to update your W-M impact scenarios and write about it. A new update will provide all of us another important and timely opportunity to remind our lregular readers, and others, that this legislation will accomplish nothing in regards to the climate: “so say the climate models.”


  6. Andrew  

    That’s odd. All the “RealClimateScientists” I have heard say it’s 2.5 “nailed” “exactly” “for sure”…but MAGICC uses 3. Hm….


  7. PaulD  

    “RC hasn’t “discredited” it yet, so it should be interesting to see whether they ever do, and if and when that happens, what they say.”

    I thought I’d pass along an interesting tidbit regarding RC and this paper. Several weeks ago RC published a post titled “Groundhog” day. They claimed that they found themselves repeated rebutting the “same-old” denier talking points and were wondering if anyone could suggest something new from the “deniers” that would be interesting to analyze. In response, I suggested that they respond to powerpoint presentation Dr. Lindzen that was posted at Watts Up With That regarding this paper. I also suggested that they respond to several interesting posts by Dr. Spencer regarding cloud feedback. My post appeared for about 30 minutes before it was deleted by the moderater.
    To give RC the benefit of the doubt I can understand why they might be reluctant to comment on a summary of paper before having the opportunity to review the published version. Still, most blogs would have simply said that rather than delete the question. I suspect that this paper is causing some concerns among real climate scientists.


  8. rbradley  

    I know that Jerry North and Andy Dessler at Texas A&M are studying the paper and look forward to their evaluation soon.


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  15. Rob  

    That’s all nice and dandy, except for the fact that Lindzen’s paper contain a colossal (deliberate?) mistake :

    He measured changes in Earth’s outbound radiation (using ERBE) and he found 4 W/m^2 change per C change in sea surface temperatures. Now that’s exactly what you would expect from Stephan Boltzmann equations for a system without feedback. So why did he conclude otherwise ?

    The problem is here :
    In his formula (and in Figure 3, pane 2) he assumes a feedback
    factor of -1 if there is NO increase in short-wave radiation.

    That is a very obvious mistake because no change in SW radiation means no feedback.

    Or differently worded : he confused radiative ‘forcing’ with it’s effect (increase in black-body radiation).

    This changes all the plots and graphs, since all numbers for SW and the ‘slope’ for the models goes up by 4 W/m^2/C, essentially becoming in line with the ERBE observations.

    More importantly, it changes the conclusion too, since there is now no measurable feeback.

    The only thing that Lindzen could conclude from the ERBE/SST data is that he found no significant feedback on the short term, and that this is in line with model predictions.



  16. Robert Bradley Jr.  

    Rob (#16)

    Here is a response from Lindzen:

    “The GRL paper does have an error though not exactly what the poster states. The issue is explained in the longer version. The zero feedback outgoing radiation for the tropics is not the same as the Planck (Stefan-Boltzmann) response for an average over the earth. See note at end of the longer piece for an explanation. However, as usual, a trivial claim will serve to ‘discredit’ the work for the true believers. That’s life.”

    The “long paper” is forthcoming in PROCEEDINGS OF THE 42ND SESSION OF THE INTERNATIONAL SEMINARS ON PLANETARY EMERGENCIES, Erice, 19-23 August 2009, a copy of which is available from the authors.


  17. Rob  

    Robert, thank you for forwarding my post to Lindzen, and Dr. Lindzen, thank you for your reply.

    I have not seen the ‘long’ version of the paper yet and I am certainly looking forward to seeing errors corrected. In this case however, that would also mean that the conclusions (about feedback and climate sensitivity and models being incorrect) need to be completely redone.

    But looking at Dr. Lindzen’s response, I doubt that the long version addresses the severity of the errors in the paper.
    Since I may not have been entirely clear in my first post, allow me to clarify how the errors in the paper nullify the conclusions that Lindzen draws.

    The main conclusions of the paper are two-fold, and my comment on them is embedded :

    (1) Lindzen claims that ERBE data shows that the Earth’s climate imposes a negative feedback mechanism (resistance to change sea-surface temperatures). He calculates feedback factor -1 overall.

    However, at 4 W/m^2/K, ERBE data is consistent with the Stephan Boltzmann derivative at the mean radiating temperature of the tropics, and thus ERBE data is consistent with a feedback factor 0.

    This mistake affects the formula where the mistake is made (in the FSW calculation) and Figure 3, pane 2 and 3.
    But most of all, this mistake changes the conclusions of the paper, regarding feedback factor and climate sensitivity.

    (2) Lindzen claims that ERBE data proves the models wrong.
    In text and in Figure 2, and table 1, Lindzen claims that ‘models’ do not match with the ERBE data. The ERBE plot shows a 4 W/m^2/K slope, while the ‘models’ show a mildly negative slope. However, in the text, Lindzen himself correctly points out that a ‘negative’ slope is physically unreal, as it would imply a climate system with infinite positive feedback. That is clearly not the case for planet Earth, and clearly not what ‘models’ predict.

    Even the simplest model (Stephan Boltzmann equation) will show a positive 4 W/m^2/K slope, in line with ERBE data.
    So I am not sure how Lindzen got to the plots for the models in Figure 2, but he is either using the wrong models (as other bloggers suspect) or he is using the right models incorrectly. Either way, Figure 2, which is so highly praised by climate sceptics, is incorrect and highly misleading.

    In reality, models predict a mildly positive feedback for the short-term, which is in the statistical error bounds of the ERBE data. Correcting this mistake (re-doing Figure 2 and table 1) nullifies the conclusion about models being incorrect.

    Besides these two major “conclusion-altering” errors, there are a few other minor problems with the paper, which should be much easier to correct :

    – In the text, Lindzen mentions that he used ERBE Edition 3 data. However, the plots (Figure 1a and 1b) show old Edition 2 graphs.

    – I would recommend that Lindzen uses the latest (rev 1) revision of the ERBE Edition 3 set, since minor corrections have been done on OLR and SW data. A quick analysis on that data shows a small reduction in OLR and a small increase in SW. Overall flux may be the same, so this data should not be conclusion altering.

    Some final notes :
    This data analysis covered short periods (of months). To extrapolation these results with conclusions about the ‘climate sensitivity’ factor when analysis’ were done over such short periods seem to be utter speculation. It seems to me that what Lindzen really found (short-term feedback factor 0, at least for the tropics) is already highly valuable to climate science by itself. There is no need to exaggerate the implications of that finding and there is certainly no need to misrepresent models or ERBE data.

    Alameda, CA


  18. Cha-am Jamal  

    i am curious to know the ipcc forecast for fossil fuel consumption in the coming 90 years that would result in a doubling of atmospheric co2. is this information freely available online? thanks in advance.


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  20. Rob  

    As promised, I contacted Dr. Lindzen himself. To my comments (above) on errors in the Lindzen and Choi paper, he writes :

    “I have great respect for people outside this field who
    bother to seriously examine matters, and we will address your
    questions explicitly as soon as we can. ”

    Now meanwhile, in a separate development, Luboš Motl picked up on my findings and contacted Dr. Roy Spencer for comment :


    Dr. Spencer published his own findings of the ERBE data yesterday, which support my criticism of Lindzen and Choi 2009 :


    In this publication, Dr. Spencer essentially points out the same problems that I found in the Lindzen and Choi paper as well :

    (1) The ERBE data shows no significant feedback
    (2) The AMIP models that Lindzen used (Graph C above) are not suitable for comparison with ERBE data
    (3) The short term analysis done makes conclusions on climate sensitivity questionable.


  21. BizzyBlog  

    […] problem is that it isn’t the only response, guys, and you know it. Cherry-pick this (HT Global Climate Scam). Comments [moderated] […]


  22. Scott Brooks  

    Rob’s reference to the Luboš Motl post omitted some feedback:

    While the champions of the climate alarm would like to make the long-term “f” more positive, I am convinced that the long-term “f” is actually smaller, or more negative, than the short-term “f”. That’s because of La Chatelier’s principle – also promoted in the context of economics by Paul Samuelson in 1947.


    It’s because the longer time scale you consider, the more processes you will find that will “adapt” to the changes and “consume” (and therefore reduce) the heat that you have added into the system. So my bet would be that the short-term “f” is very close to zero and the long-term “f” is somewhat negative.

    So Luboš basically agrees with Lindzen’s observation that the IPCC has over emphasized the CO2 forcing.


  23. JJ - Sukces Osobisty?  

    @Scott Brooks
    Any further info from Dr Lindzen? I’m very curious what is the conclusion?

    [RLB: The paper, according to Lindzen, has been revised and returned to JGR.”]


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