date: Wed Jun 25 13:40:32 2003 from: Keith Briffa subject: Fwd: Re: ice cores/China series to: t.osborn@uea.ac.uk Date: Wed, 25 Jun 2003 06:36:45 -0600 From: Tom Wigley User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.0.1) Gecko/20020823 Netscape/7.0 X-Accept-Language: en-us, en To: Keith Briffa Subject: Re: ice cores/China series KEITH -- SEE BELOW Keith Briffa wrote: 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" . YEAH, I REALIZE THIS -- AND I AGREE THAT IT WAS IMPORTANT TO GET THE DOCUMENT OFF QUICKLY. 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. YOU MISUNDERSTAND ME. OF COURSE IT WOULD BE SILLY TO SINGLE OUT A SPECIFIC ITEM. WHAT IS NECESSARY IS A SENTENCE STATING THE *METHOD* -- I.E., THAT ITEMS ARE WEIGHTED BY THEIR CALIBRATION PERFORMANCE. 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?) . IT IS A DIFFICULT CALL -- WHETHER TO DUMP SERIES THAT HAVE NO SIGNIFICANT LINK TO TEMPERATURE AND WHICH ARE, AS WELL, DUBIOUS ON A PRIORI GROUNDS; OR TO USE A WEIGHTING SCHEME. IF ONE DID THIS BY SIMPLE MULTIPLE REGRESSION, THEN THINGS WOULD BE WEIGHTED AUTOMATICALLY. HOWEVER, STATISTICALLY ONE SHOULD STILL DUMP THE LOW CORRELATION ONES. I HAVE RESERVATIONS ABOUT WHAT MIKE AND PHIL HAVE DONE -- BUT THIS IS SOMETHING WE SHOULD TALK ABOUT FACE TO FACE SOME DAY. 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. YEAH. At this stage , singling out individual records for added (and unavoidably cursory added description) is not practical. I AM NOT SUGGESTING THIS -- AS THE ABOVE SHOULD MAKE CLEAR. 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. NO -- I'M HAPPY WITH KEEPING THINGS AT THIS LEVEL. Best wishes Keith I WAS AT A MEETING IN BRECKENRIDGE YESTERDAY WHERE SUSAN SOLOMON GAVE AN HOUR LONG PRESENTATION ABOUT PLANS FOR THE 4AR WG1 REPORT, DUE OUT IN 2007. IT WAS A COMPREHENSIVE TALK -- AND SHE HAS THINGS MUCH BETTER ORGANIZED THAT JOHN HOUGHTON EVER DID. SHE DID SINGLE OUT TREE RINGS AS A VITAL COMPONENT OF THE PALEO RECORD. 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 Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [2]http://www.cru.uea.ac.uk/cru/people/briffa[3]/