Tuesday, December 20, 2011


From: Jonathan Overpeck <jto@u.arizona.edu>
To: Keith Briffa <k.briffa@uea.ac.uk>
Subject: Fwd: divergence
Date: Wed, 8 Mar 2006 15:18:54 -0700
Cc: ralley@geosc.psu.edu, Eystein Jansen <eystein.jansen@geo.uib.no>, Bette Otto-Bleisner <ottobli@ncar.ucar.edu>, joos <joos@climate.unibe.ch>, t.osborn@uea.ac.uk, "Ricardo Villalba" <ricardo@lab.cricyt.edu.ar>

Hi gang - Richard is raising important issues, and Keith is going to
respond in some detail on Friday when he gets back. I am cc'ing this
to a broader group of IPCC Chap 6 folks so that we make sure we (chap
6) deal with the issues correctly. I'm hoping that Keith will cc to
us all, and we'll go from there.

For those just in on the issue raised by Richard. There is a paper
written by Rosanne D'Arrigo that apparently casts serious doubt on
the ability of tree ring data to reconstruct the full range of past
temperature change - particularly temperatures above mid-20th century
levels. Chap 6 obviously has to deal with this more in the next
draft, so Eystein and I would like to get on top of it starting this

Keith or Richard - do you have a copy of this paper? Is it accepted?

Thanks, Peck

>X-Sieve: CMU Sieve 2.2
>Date: Wed, 8 Mar 2006 11:55:46 -0500 (EST)
>From: <ralley@geosc.psu.edu>
>To: jto@u.arizona.edu
>Cc: k.briffa@uea.ac.uk
>Subject: divergence
>Peck--Thanks. The big issue may be that you don't just have to convince me
>now; if the NRC committee comes out as being strongly negative on the
>hockey stick owing to RD'A's talk, then the divergence between IPCC and NRC
>will be a big deal in the future regardless. The NRC committee is accepting
>comments now (I don't know for how long)... As I noted, my observations
>of the NRC committee members suggest rather strongly to me that they now
>have serious doubts about tree-rings as paleothermometers (and I do,
>too...at least until someone shows me why this divergence problem really
>doesn't matter). --Richard

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

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