cc: carl mears <mears@remss.com>, Phil Jones <p.jones@uea.ac.uk>, santer1@llnl.gov, Tom Wigley <wigley@cgd.ucar.edu>, "Thorne, Peter" <peter.thorne@metoffice.gov.uk>, Steven Sherwood <Steven.Sherwood@yale.edu>, John Lanzante <John.Lanzante@noaa.gov>, "'Dian J. Seidel'" <dian.seidel@noaa.gov>, Melissa Free <Melissa.Free@noaa.gov>, Frank Wentz <frank.wentz@remss.com>
date: Tue, 04 Dec 2007 15:59:43 -0700
from: Tom Wigley <wigley@ucar.edu>
subject: Re: [Fwd: sorry to take your time up, but really do need a  scrub
to: Karl Taylor <taylor13@llnl.gov>

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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
>>>>> ---------------------------------------------------------------------------- 
>>>>>
>>>>>
>>>>>
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>>>>> 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 <anrevk@nytimes.com>
>>>>> 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
>>>>> <http://www.nytimes.com/revkin>_*The New York Times / Environment 
>>>>> / Dot Earth <http://dotearth.blogs.nytimes.com/>Blog
>>>>> <http://dotearth.blogs.nytimes.com/>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))
>>>
>>
>
>
>


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