Thursday, May 17, 2012


cc: Keith Briffa <>,,, Fortunat Joos <>,,
date: Wed, 1 Mar 2006 09:07:28 -0700
from: Jonathan Overpeck <>
subject: Re: latest draft of 2000-year section text
to: Tim Osborn <>

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

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.
>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:
>>(My former addresses are read by my assistant Brigitta.)
>>Stefan Rahmstorf
>Dr Timothy J Osborn
>Climatic Research Unit
>School of Environmental Sciences, University of East Anglia
>Norwich NR4 7TJ, UK
>phone: +44 1603 592089
>fax: +44 1603 507784

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

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