James Annan’s Second Thoughts on Atmospheric Sensitivity

James Annan is a scientist is a scientist who is a member of the Global Change Projection Research Programme at RIGC. His work is frequently cited in the blogosphere by the activist community, as he more or less declared some years back that atmospheric sensitivity to a doubling of CO2 concentrations was 3C, and he was pretty definitive about it.

The performance of several climate parameters over the past decade has caused him to rethink his view on the subject of atmospheric sensitivity and he posted his newer views on his weblog today.

Money quote: “the additional decade of temperature data from 2000 onwards (even the AR4 estimates typically ignored the post-2000 years) can only work to reduce estimates of sensitivity, and that’s before we even consider the reduction in estimates of negative aerosol forcing, and additional forcing from black carbon (the latter being very new, is not included in any calculations AIUI). It’s increasingly difficult to reconcile a high climate sensitivity (say over 4C) with the observational evidence for the planetary energy balance over the industrial era.”

For Lukewarmers it is welcome support for our views of a lower value for sensitivity.

We’ll get back to Matt Ridley’s questions later.


17 responses to “James Annan’s Second Thoughts on Atmospheric Sensitivity

  1. Maybe we need a new category named midwarmer.

    • Paul, what is truly maddening is that any sensitivity that is positive, no matter how small, is invariably a reason to mitigate for CO2. I know of no Lukewarmer (Tom, maybe you do) that is not CO2-Centric. CO2 centrism is so ingrained in the popular culture, that none of the benefits of the greatest life-giving molecule on planet earth will be espoused for a long time. But Lukewarmism is at least a step in the right direction. We just have to work hard on the CO2=Bad thing.

      • Not necessarily. I think Tom is conflating issues here. A Lukewarmer looking at the empirical evidence concludes warming > 2C is improbable. But the second claim that warming < 2C is bad for humanity and/or the environment are separate arguments. Maybe I'm being unkind but my impression is that Tom thinks it's bad because it's the social fad right now to make such an assumption.

      • Hi Will–I may be following fashion. It’s always hard to say how objective one is being about one’s own thoughts. But I have thought about it. A lot. You might check out 3000 Quads if you haven’t already. At least there I show my work…

      • To a certain degree it becomes a shorthand symbol of all human effects on climate–maybe we fall too easily into that trap. I certainly am concerned about deforestation and other land use changes.

      • Will,

        My impression of Tom always has been he believes in low sensitivity but at the same time believes that the A1F1 emissions scenario is likely.

        Hence…3000 quads…if it all comes from coal we are cooked.

    • Hiya Paul! Maybe we could use Marmer?

  2. It seems that faith in the best climate sensitivity estimate is determined to a large degree by temperature trends over the previous decade. That is not confidence inspiring.

  3. To many people, the money quote was about the scientist lying about climate sensitivity:

    “The paper I refer to as a “small private opinion poll” is of course the Zickfeld et al PNAS paper. The list of pollees in the Zickfeld paper are largely the self-same people responsible for the largely bogus analyses that I’ve criticised over recent years, and which even if they were valid then, are certainly outdated now. Interestingly, one of them stated quite openly in a meeting I attended a few years ago that he deliberately lied in these sort of elicitation exercises (i.e. exaggerating the probability of high sensitivity) in order to help motivate political action. Of course, there may be others who lie in the other direction, which is why it seems bizarre that the IPCC appeared to rely so heavily on this paper to justify their choice, rather than relying on published quantitative analyses of observational data.”


    • I agree. Annan mentions it like it is no big deal to tell lies to “motivate political action”. The New Normal, I guess.

      Annan also thinks that it is “bizarre” that the IPCC relied heavily on this paper. It is only bizarre if the IPCC knew about the validity of claims of this paper. Makes sense if the same people who think lies are OK are involved with IPCC reports…. leading climate scientists, you know?

    • Yes, I agree, but for a totally different reason.

      What is compelling to me is not the statement itself, but the lack of reaction to it. The MSM, and even the climate blogs, reacted to this statement with a collective yawn. It’s barely newsworthy. I’ve got to assume that Annan was expecting this part of his to post to be pounced on.

      What does that say about the state of climate science? It says that it is *** accepted *** that political activism in climate science is built in.

      The real question to me is: Who is supposed to be policing this type of activism? It clearly taints the science and results in a public lack of trust. Somebody should care, do they? The IPCC is obviously part of the problem, not the solution. NAS, AAAS?

      • Who is supposed to be policing this type of activism? It clearly taints the science and results in a public lack of trust. Somebody should care, do they? The IPCC is obviously part of the problem, not the solution. NAS, AAAS?

        I very much doubt that it will be the AAAS. On the heels of Gleickgate, according to the U.K. Guardian (unless things have changed on the Green-Is-Great-Front in the last year, and I’ve seen no significant indications of that!):

        Attacks paid for by big business are ‘driving science into a dark era‘

        Researchers attending one of the world’s major academic conferences ‘are scared to death of the anti-science lobby’

        [and underneath pic of obligatory polar bear:]

        The vast majority of scientists on both sides of the Atlantic say rising levels of carbon dioxide in the atmosphere threaten to increase temperatures to dangerous levels.
        Most scientists, on achieving high office, keep their public remarks to the bland and reassuring. Last week Nina Fedoroff, the president of the American Association for the Advancement of Science (AAAS), broke ranks in a spectacular manner.

        She confessed that she was now “scared to death” by the anti-science movement that was spreading, uncontrolled, across the US and the rest of the western world.

        “We are sliding back into a dark era,” she said. “And there seems little we can do about it. I am profoundly depressed at just how difficult it has become merely to get a realistic conversation started on issues such as climate change or genetically modified organisms.”

        And, unless I’m mistaken, NAS is the “home” of PNAS – promulgator of that abysmal excuse for a “paper” by Anderegg et al.

        So, not much hope there either, I’m afraid.

  4. Fred from Canuckistan . . .

    He still has a long way to climb down from his previous claims.

    Maybe he figures his reputation is in jeopardy and he needs to start accepting the reality of data over his preferences of models.

    Because data always prevails.

    • Hi Fred,

      If what he posted on his blog is any indication, he doesn’t think he’s climbing down. The thrust of what he’s written is (at least to him) to lower the chance of fat tail outcomes above 4.5C. He seems to feel that sensitivity remains between the 3C he thinks he can get away with claiming and the 2.5C that he would like to advance if he could do so without fear.

      I’m going to post again on this, as in all truth, removing the fat tails is far more important than showing another calculation for sensitivity, even if it is a bit lower than those of his colleagues.

      • Yeah, moving from a “best estimate” of 3C to ~2.5C isn’t that much of a change. It’s just tightening the range within the original IPCC estimates of 2-4.5C.

        At this point, it’s much more important to improve our understanding of what 2.5 or 3 C *means* for us, particularly in terms of hydrological cycle. It may turn out that we have less cooling than we thought, but worse floods/droughts. We just don’t know yet.

        Although, it will indeed be a relief if the fat tail is gone. That removes some of the worst-case scenarios from the board – which were never really likely to begin with, but hopefully the discussion can move away from “oh noes the sky is falling” and more towards rational, calm cost-benefit analysis: “the cost of inaction is X times greater than the cost of action”. Honestly, the hyperbole turns off a lot of people who would have otherwise been already convinced by the science.

  5. Annan has previously bet against Joe Romm on sea ice. He was a lukewarmer before everyone.

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