cc: Keith Briffa <k.briffa@uea.ac.uk>, jto@u.arizona.edu, eystein.jansen@geo.uib.no, Fortunat Joos <joos@climate.unibe.ch>, drind@giss.nasa.gov, rahmstorf@ozean-klima.de
date: Wed, 1 Mar 2006 09:07:28 -0700
from: Jonathan Overpeck <jto@u.arizona.edu>
subject: Re: latest draft of 2000-year section text
to: Tim Osborn <t.osborn@uea.ac.uk>

<x-flowed>
All - yes, it's great that the Wahl et al papers (both in Science, 
and in CChange) were accepted this week. These both help clarify the 
issues.

Thanks, peck

>Hi again Stefan,
>
>I'm sympathetic to many of these points that you make.  Obviously 
>only the scientific literature can be covered in the chapter, rather 
>than the interpretation or testimony that appeared elsewhere.  Given 
>that the bias appears real, though of unknown magnitude, I think we 
>should include a citation to the new comment (Wahl et al.) along 
>with the existing citations that are given at the end of the 
>existing text that states that the extent of the bias is uncertain.
>
>Cheers
>
>Tim
>
>At 17:32 28/02/2006, Stefan Rahmstorf wrote:
>>Hi Tim,
>>
>>my simplistic interpretation as an outside observer of this field is:
>>
>>VS04 published a high-profile analysis in Science concluding that 
>>the performance of the MBH method is disastrously bad. 
>>Subsequently, VS in the media called the MBH result "nonsense", 
>>accused Nature of putting their sales interests above peer review 
>>when publishing MBH, and called the IPCC "stupid" and 
>>"irresponsible" for highlighting the results of MBH. This had 
>>*major* political impact - I know this e.g. from EU negotiators who 
>>were confronted with this stuff by their US colleagues.
>>
>>Then it turns out that they implemented the method incorrectly. If 
>>it is done as MBH did, variance is still somewhat underestimated in 
>>the same pseudoproxy test, but only a little, within the error bars 
>>given by MBH and shown by IPCC. Certainly nothing dramatic - one 
>>could conclude that the method works reasonably well but needs 
>>improvement. This would have been a technical discussion with not 
>>much political impact.
>>
>>What VS and their colleagues are doing now, rather than publishing 
>>a correction of their mistake, is saying: "well, but if we add a 
>>lot more noise, or use red noise, then the MBH method is still 
>>quite bad..."
>>
>>The question here is: should our IPCC chapter say something to 
>>correct the wrong impression which had the political impact, namely 
>>that the MBH method is disastrously bad? This is not the same as 
>>the legitimate discussion about the real errors in proxy 
>>reconstructions, which accepts that these reconstructions have some 
>>errors but are still quite useful, rather than being "nonsense".
>>
>>Cheers, Stefan
>>
>>--
>>To reach me directly please use: 
>><mailto:rahmstorf@ozean-klima.de>rahmstorf@ozean-klima.de
>>(My former addresses @pik-potsdam.de are read by my assistant Brigitta.)
>>
>>Stefan Rahmstorf
>><http://www.ozean-klima.de>www.ozean-klima.de
>>www.realclimate.org
>
>Dr Timothy J Osborn
>Climatic Research Unit
>School of Environmental Sciences, University of East Anglia
>Norwich  NR4 7TJ, UK
>
>e-mail:   t.osborn@uea.ac.uk
>phone:    +44 1603 592089
>fax:      +44 1603 507784
>web:      http://www.cru.uea.ac.uk/~timo/
>sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm


-- 
Jonathan T. Overpeck
Director, Institute for the Study of Planet Earth
Professor, Department of Geosciences
Professor, Department of Atmospheric Sciences

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