from: Keith Briffa <k.briffaatXYZxyz.ac.uk>
subject: ice cores/China series
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.
Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.