Sensitivity by Schwartz, and Irreducible imprecision

Posted by William M. Connolley on August 19, 2007
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JA has a nice entry on Schwartz’ sensitivity estimate pointing out where the probable errors are.

I too found the 5-y timescale rather low. Fitting in with James’s assessment that S is wandering out of his field, I was surprised by the lack of discussion of how this new result fits in with everyone else’s answers. There is a brief note that “This climate sensitivity is much lower than current estimates, e.g., the Fourth Assessment Report of the Intergovernmental Panel on Climate Change…” but that seems to be about it.

Meanwhile, Irreducible imprecision in atmospheric and oceanic simulations (thanks to JR) may be interesting, though I haven’t read it yet.

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Comments

  1. #1 crandles
    2007/08/19

    “Simplistically, despite the opportunistic assemblage of the various AOS model ensembles, we can view the spreads in their results as upper bounds on their irreducible imprecision. Optimistically, we might think this upper bound is a substantial overestimate because AOS models are evolving and improving. Pessimistically, we can worry that the ensembles contain insufficient samples of possible plausible models, so the spreads may underestimate the true level of irreducible imprecision (cf., ref. 23). Realistically, we do not yet know how to make this assessment with confidence. ”

    Reads to me as ‘we haven’t got a clue’. While

    “Whether or not the irreducible imprecision proves to be a substantial fraction of present AOS discrepancies with nature, it seems imperative to determine what the magnitude of this type of imprecision is. ”

    sounds like ‘it is imperative so that I will then be an expert’. Another paper concluding what the author wants to conclude? But maybe that is a bit too cynical.

    Anyway despite above comments, I think I would agree that it may be interesting.

  2. #2 Eli Rabett
    2007/08/20

    I think I’ve made the point that all sorts of models at all sorts of levels keep yielding the same range of temperature sensitivity for a century and there is no reason to expect the situation to improve; However, what we have is suffieicnt for poicy purposes. More research will not improve the estimate, only fill in details