cc: Keith Briffa , jto@u.arizona.edu, eystein.jansen@geo.uib.no, Fortunat Joos , drind@giss.nasa.gov, rahmstorf@ozean-klima.de 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 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: >>rahmstorf@ozean-klima.de >>(My former addresses @pik-potsdam.de are read by my assistant Brigitta.) >> >>Stefan Rahmstorf >>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 Mail and Fedex Address: Institute for the Study of Planet Earth 715 N. Park Ave. 2nd Floor University of Arizona Tucson, AZ 85721 direct tel: +1 520 622-9065 fax: +1 520 792-8795 http://www.geo.arizona.edu/ http://www.ispe.arizona.edu/