From	Michael E. Mann	Date	Tue, 24 Jun 2003 14:06:25 -0400
To	Keith Briffa, Phil Jones, ray bradley
CC	Michael E. Mann
Subject	Re: ice cores/China series (FYI)
Thanks Keith, I just read your email after reading the others. We actually eliminate records with negative correlations (this is mentioned breifly in the GRL article,), and we investigated a variety of weighting schemes to assure the basic robustness of the composite--but I certainly endorse your broader point here. Many of these records have some significant uncertainties or possible sources of bias, and this isn't the place to get into that. The uncertainties get at this, at some level, and other places (e.g. the Reviews of Geophysics paper Phil and I are drafting) will provide an opportunity to discuss these kinds of issues in more detail--we will certainly be seeking advice (either officially or unofficially) from each of you once we have finalized the draft of that... Now back to my honeymoon... mike At 02:38 PM 6/24/2003 +0100, Keith Briffa wrote: To keep you informed , here is a reply to Tom Wigley re his request to "deal with Ray's Comments" re the China series in EOS piece Tom Tim has just told me of your message expressing concern about the China series , and your statement of the necessity to "deal with Ray's comment" and add in the "small adjustment to the Figure Caption". . We (I and Tim) decided to get this off as soon as possible to Ellen (AGU) , as we had been asked to do (and as requested by Ellen). Hence it went off earlier today (and before your message arrived). Mike was aware of Ray's comment and was happy to leave any amendment to the text "until the proof stage" . In my opinion it is not practical (or desirable) to try to "qualify " any one record in this limited format. It was a majority decision to leave the Mann and Jones 2000-year series in the Figure 1 (as it was to remove the Briffa and Osborn tree-ring based one) , and the details of the logic used to derive the Mann and Jones series is to be found in the (cited) text of their paper. Signing on to this letter , in my mind. implies agreement with the text and not individual endorsement of all curves by each author. I too have expressed my concern to Phil (and Ray) over the logic that you leave all series you want in but just weight them according to some (sometimes low) correlation (in this case based on decadal values). I also believe some of the series that make up the Chinese record are dubious or obscure , but the same is true of other records Mann and Jones have used (e.g. how do you handle a series in New Zealand that has a -0.25 correlation?) . Further serious problems are still (see my and Tim's Science comment on the Mann 1999 paper) lurking with the correction applied to the Western US tree-ring PC amplitude series used (and shown in Figure 2). There are problems (and limitations ) with ALL series used. At this stage , singling out individual records for added (and unavoidably cursory added description) is not practical. We were told to cut the text and References significantly - and further cuts are implied by Ellen's messages to us. If you wish to open this up to general discussion , it may be best to wait 'til the proof stage and then we can all consider the balance of emphasis - but we had also better guard against too "selective" a choice of data to present? If you want to get a somewhat wider discussion of this point going in the meantime , feel free to forward this to whoever you wish along with your disagreement , while we wait on the response from AGU. Best wishes Keith Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [1]http://www.cru.uea.ac.uk/cru/people/briffa/ ______________________________________________________________ Professor Michael E. Mann Department of Environmental Sciences, Clark Hall University of Virginia Charlottesville, VA 22903 _______________________________________________________________________ e-mail: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137 [2]http://www.evsc.virginia.edu/faculty/people/mann.shtml References 1. http://www.cru.uea.ac.uk/cru/people/briffa/ 2. http://www.evsc.virginia.edu/faculty/people/mann.shtml