Monday, December 12, 2011


From: Keith Briffa <>
To: Kevin Trenberth <>, "Michael E. Mann" <>
Subject: Re: draft
Date: Mon Oct 13 16:36:52 2003
Cc: Caspar Ammann <>,,,,,,, Scott Rutherford <>, Tom Wigley <>,

Mike and all
Hi , just back from a trip and only now catching up with important emails. Given
the restricted time and space available to furnish a response to SB comments ,
I offer the following mix of comment and specific wording changes:
I agree that the S+B response is designed to deflect criticism by confusing the issues
rather than answering our points.
In fact they fail to address any of the 3 specific
issues we raised Namely , 1. the need for critical evaluation of proxy inputs , 2. the
need for a consistent assimilation of widespread (dated and well resolved ) records,
3. the essential requirement for objective/quantitative calibration (scaling) of the input
records to allow for assessment of the uncertainties when making
comparisons of different reconstructions and when comparing early with recent
Their own , ill-conceived and largely subjective approach did not take
account of the uncertainties and problems in the use of palaeodata that they chose to
highlight in their opening remarks.
I would be in favour of stating something to this effect at the outset of our response.
Also , as regards the tree-ring bit , I fully concur with the sense of your text as
regards Section 1, but suggest the following wording (to replace ",rarely for annual
ring widths, and almost entirely at higher latitudes.")
"but in certain high-latitude regions only. Where this is the case , these relatively
(ie post 1950) data are not used in calibrating temperature reconstructions. In many other
(even high-latitude) areas density or ring-width records display no bias."
In the spirit of healthy debate - I agree with Tim's remarks , warning against presenting a
sanguine impression that the borehole debate is closed ( though I do think it is closing!).
I also believe , as you already know, that the use of a recent padding algorithm to extend
smoothed data to the present time, is inappropriate if it assumes the continuation of a
trend. This is likely to confuse , rather than inform, the wider public about the current
climate state .
Finally , I repeat my earlier remarks (made before EOS piece published) that we are missing
an opportunity to say that a warm Medieval period per se is not a refutation of
warming , {as its absence is no proof}, if we do not understand the role of specific
forcings (natural
and anthropogenic) that influenced medieval and current climates.
At 12:48 PM 10/9/03 -0600, Kevin Trenberth wrote:

Hi all
Here are my suggested changes: toned down in several places. Tracking turned on
Michael E. Mann wrote:

Dear co-authors,
Attached is a draft response, incorporating suggestions Kevin, Tom W, and Michael. I've
aimed to be as brief as possible, but hard to go much lower than 750 words and still
address all the key issues. 750 words, by the way, is our allotted limit.
Looking forward to any comments. Feel free to send an edited version if you prefer, and
I'll try to assimilate all of the suggested edits and suggestions into a single revised
draft. If you can get comments to me within the next couple days, that would be very
helpful as we're working on a late October deadline for the final version.
Thanks for your continued help,
Professor Michael E. Mann
Department of Environmental Sciences, Clark Hall
University of Virginia
Charlottesville, VA 22903
e-mail: [1] Phone: (434) 924-7770 FAX: (434) 982-2137

Kevin E. Trenberth e-mail: [3]
Climate Analysis Section, NCAR [4]
P. O. Box 3000, (303) 497 1318
Boulder, CO 80307 (303) 497 1333 (fax)

Street address: 1850 Table Mesa Drive, Boulder, CO 80303

Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.

Phone: +44-1603-593909
Fax: +44-1603-507784



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