the Air Vent

Because the world needs another opinion

Questioning the Forest et al. (2006) sensitivity study

Posted by Jeff Id on June 25, 2012

Nic Lewis has spent a great deal of time analyzing this important paper in climate science. He has posted an article at Climate etc., readers may comment here or there, Nic will be around to answer technical quesitons.  — Jeff

Questioning the Forest et al. (2006) sensitivity study

by Nicholas Lewis

7 Responses to “Questioning the Forest et al. (2006) sensitivity study”

  1. ferd berple said

    How to make Money in Climate Science

    1. find a major unanswered question.
    3. question top scientists to see what they will accept as an answer
    3. cherry pick data and methods to arrive at that answer
    4. re-label this technique “training” – it makes it sound intelligent.
    5. publish the result.

    The results will seem correct to fellow scientists, especially those at the top, so they wont bother to check the math. Everyone will be impressed you have answered the hard question. More so because you will have proven their best guess correct and made them look good in the process. You will advance in your career in science. Fame and fortune will follow.

    If anyone does question the results:

    6. stall – play for time – they will likely give-up.
    7. if not – lose the data and methods

  2. j ferguson said

    Fred, that is really good. might even be accurate.

  3. stan said

    I doubt many people here would disagree with the idea that government policy makers should never consider any science which is based on studies that are not completely transparent and capable of audit and replication. The people should never have their rights infringed on the basis of secret evidence, even if scientists don’t seem to have any problem with the secrecy. Unfortunately, this doesn’t seem to have penetrated the climate science cocoon.

    I am curious why scientists seem to think it perfectly acceptable to foist this secret stew on the public. Is it simple cluelessness? I know I’ve frequently accused them of gross hubris, but I’m not sure that hubris is sufficient an explanation.

  4. timetochooseagain said

    Nic Lewis’s audit of the IPCC’s “sensitivity” PDFs is greatly appreciated. I asked him a few questions at WUWT, it seems the interest came about because the PDFs had weird nonsensical shapes. The “fat tail” occurs because of equation (8) in the Differential Equations post. Recall I said:

    “This means that as long as f is positive, slight variations in its value lead to large variations in sensitivity, which is why the range of sensitivities typically given is usually quite large, but if the feedback is negative, even large relative errors in the size of the value of f lead to a small uncertainty band about a low sensitivity.”

    However, Nic has informed me of two things:

    1. The IPCC’s PDFs have odd local maxima and “shoulders” that require bizarre distributions (multimodal, non-normal, etc) for f which make zero sense. Only one is consistent with a normally distribute value for f
    2. The IPCC has apparently altered or even create from essentially whole cloth the PDFs shown (arbitrary truncation and scaling, in one case by multiplying by sensitivity squared(!) and taking a coarse histogram of a bunch of unweighted models and somehow “smoothing” it into a “PDF” (this I call creation out of whole cloth).

    In short, a key chart of the IPCC purporting to support it’s estimates of sensitivity is dubious to begin with. Now add that this particular study appears to not be replicable, and there is increasingly little reason to believe their estimates are credible anymore.

  5. Carrick said

    Another couple of papers to consider is Annan and Hargreaves. Also this.

    It would be interesting to see Nic provide more details for his “low ball” estimate of climate sensitivity.

    • timetochooseagain said

      Annan’s work seems to place a great deal of significance on the transition from the last glacial maximum. I’m still trying to figure out how it makes sense to look at changes due to spatially heterogeneous forcing with the “global mean sensitivity” and “global mean TOA radiative forcing.” Such work “explains” the glacial cycles as “caused” by the slow feedbacks…

  6. Brian H said

    Too bad. We could’a used more to resist the ice sheets.

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