cc: carl mears , Phil Jones , santer1@llnl.gov, Tom Wigley , "Thorne, Peter" , Steven Sherwood , John Lanzante , "'Dian J. Seidel'" , Melissa Free , Frank Wentz date: Tue, 04 Dec 2007 15:59:43 -0700 from: Tom Wigley subject: Re: [Fwd: sorry to take your time up, but really do need a scrub to: Karl Taylor Good points, Karl. (Boy -- lucky our K/Carls have different spellings.) We can talk about this when I'm at PCMDI on Thursday. Tom. =================== Karl Taylor wrote: > Dear all, > > To expand on what Carl and Tom have said, what Douglass et al. show, I > think, is that the *mean* of model results is inconsistent with > observations above the surface, under the assumptions that > > 1) the individual models are taken as independent, and > 2) unforced variability hasn't dominated the observations. > > Note that in the models, unforced variability is not as much of an > issue because Douglass et al. have considered the ensemble mean when > more than 1 realization was available from a model and across models > the unforced variability will tend cancel out. One could look at the > inter-ensemble variations from individual models to get an idea on the > likely magnitude of unforced variability. > > Douglass et al. have *not* shown that every individual model is in > fact inconsistent with the observations. If the spread of individual > model results is large enough and at least 1 model overlaps the > observations, then one cannot claim that all models are wrong, just > that the mean is biased. > > My own gut feeling is that models as a group probably do indeed have a > significant bias in simulating upper air temperature trends (but I > don't know if that has influenced the climate sensitivity in a > systematic way). As I recall, however, some individual models appear > to be reasonably consistent with observations (within likely > observational errors and variability). It remains an interesting > problem then to track down why there is a mean bias and check whether > that bias has any important implications. > > A response to Douglass et al. should certainly point out the reason > why it is appropriate to look at the range of model results for > purposes of determining whether individual models are consistent with > observations. > > cheers, > Karl > > > The observations, if > > Tom Wigley wrote: > >> All, >> >> Depends on whether the runs are independent. Are models independent? >> >> A billion runs would indeed reduce the statistical uncertainty to near >> zero. What is left (if one compared with absolutely correct observed >> data) >> is the mean model bias. >> >> Tom. >> >> ++++++++++++++++++ >> >> carl mears wrote: >> >>> Hi Ben, Phil and others >>> >>> To me, the fundamental error is 2.3.1. Expecting the observed >>> values to lie within >>> +/- 2*sigma(SE) (i.e. sigma/(sqrt(N-1)) of the distribution of N >>> model trends) is just >>> wrong. >>> If this were correct, we could just run the models a lot of times, >>> say a billion or so, and have a >>> very, very, very small sigma(SE) (assuming the sigma didn't grow >>> much) and we'd never >>> have "agreement" with anything. Absurd. >>> >>> Does IJC publish comments? >>> >>> -Carl >>> >>> At 02:09 AM 12/4/2007, Phil Jones wrote: >>> >>>> Ben, >>>> It sure does! Have read briefly - the surface arguments are wrong. >>>> I know editors have difficulty finding reviewers, but letting this >>>> one >>>> pass is awful - and IJC was improving. >>>> >>>> Cheers >>>> Phil >>>> >>>> >>>> At 17:53 30/11/2007, Ben Santer wrote: >>>> >>>>> Dear folks, >>>>> >>>>> I'm forwarding this to you in confidence. We all knew that some >>>>> journal, somewhere, would eventually publish this stuff. Turns out >>>>> that it was the International Journal of Climatology. Strengthens >>>>> the need for some form of update of the Santer et al. (2005) >>>>> Science paper. >>>>> >>>>> With best regards, >>>>> >>>>> Ben >>>>> ---------------------------------------------------------------------------- >>>>> >>>>> Benjamin D. Santer >>>>> Program for Climate Model Diagnosis and Intercomparison >>>>> Lawrence Livermore National Laboratory >>>>> P.O. Box 808, Mail Stop L-103 >>>>> Livermore, CA 94550, U.S.A. >>>>> Tel: (925) 422-2486 >>>>> FAX: (925) 422-7675 >>>>> email: santer1@llnl.gov >>>>> ---------------------------------------------------------------------------- >>>>> >>>>> >>>>> >>>>> X-Account-Key: account1 >>>>> Return-Path: >>>>> Received: from mail-2.llnl.gov ([unix socket]) >>>>> by mail-2.llnl.gov (Cyrus v2.2.12) with LMTPA; >>>>> Fri, 30 Nov 2007 08:39:49 -0800 >>>>> Received: from smtp.llnl.gov (nspiron-3.llnl.gov [128.115.41.83]) >>>>> by mail-2.llnl.gov (8.13.1/8.12.3/LLNL evision: 1.6 $) >>>>> with ESMTP id lAUGdl5E004790 >>>>> for ; Fri, 30 Nov 2007 08:39:48 -0800 >>>>> X-Attachments: DCPS-proofs_IJC07.pdf >>>>> X-IronPort-AV: E=McAfee;i="5100,188,5173"; a="21323766" >>>>> X-IronPort-AV: E=Sophos;i="4.23,235,1194249600"; >>>>> d="pdf'?scan'208,217";a="21323766" >>>>> Received: from nsziron-1.llnl.gov ([128.115.249.81]) >>>>> by smtp.llnl.gov with ESMTP; 30 Nov 2007 08:39:47 -0800 >>>>> X-Attachments: DCPS-proofs_IJC07.pdf >>>>> X-IronPort-AV: E=McAfee;i="5100,188,5173"; a="6674079" >>>>> X-IronPort-AV: E=Sophos;i="4.23,235,1194249600"; >>>>> d="pdf'?scan'208,217";a="6674079" >>>>> Received: from smtp-nv-vip1.nytimes.com (HELO nytimes.com) >>>>> ([199.181.175.116]) >>>>> by nsziron-1.llnl.gov with ESMTP; 30 Nov 2007 08:39:43 -0800 >>>>> Message-Id: <6.2.5.6.2.20071130111858.03540590@nytimes.com> >>>>> X-Mailer: QUALCOMM Windows Eudora Version 6.2.5.6 >>>>> Date: Fri, 30 Nov 2007 11:38:52 -0500 >>>>> To: santer1@llnl.gov, broccoli@envsci.rutgers.edu, mears@remss.com >>>>> From: Andrew Revkin >>>>> Subject: sorry to take your time up, but really do need a scrub of >>>>> this >>>>> singer/christy/etc effort >>>>> Mime-Version: 1.0 >>>>> Content-Type: multipart/mixed; >>>>> boundary="=====================_67524015==_" >>>>> X-NYTOriginatingHost: [10.149.144.50] >>>>> >>>>> hi, >>>>> for moment please do not distribute or discuss. >>>>> trying to get a sense of whether singer / christy can get any >>>>> traction with this at all. >>>>> >>>>> >>>>> >>>>> *_ ANDREW C. REVKIN >>>>> _*The New York Times / Environment >>>>> / Dot Earth Blog >>>>> 620 Eighth Ave., NY, NY >>>>> 10018-1405 >>>>> phone: 212-556-7326 fax: 509/ /-357-0965 mobile: 914-441-5556 >>>> >>>> >>>> >>>> Prof. Phil Jones >>>> Climatic Research Unit Telephone +44 (0) 1603 592090 >>>> School of Environmental Sciences Fax +44 (0) 1603 507784 >>>> University of East Anglia >>>> Norwich Email p.jones@uea.ac.uk >>>> NR4 7TJ >>>> UK >>>> ---------------------------------------------------------------------------- >>> >>> >>> >>> >>> >>> >>> Dr. Carl Mears >>> Remote Sensing Systems >>> 438 First Street, Suite 200, Santa Rosa, CA 95401 >>> mears@remss.com >>> 707-545-2904 x21 >>> 707-545-2906 (fax)) >>> >> > > >