cc: t.osborn@uea.ac.uk,p.jones@uea.ac.uk
date: Mon Jul 18 12:22:19 2005
from: Keith Briffa <k.briffa@uea.ac.uk>
subject: Re: crowley
to: Tom Wigley <wigley@cgd.ucar.edu>

   as a first quick response - the Crowley numbers came from his paper with Lowery. I seem to
   remember that there were 2 versions of the composite that he produced - certainly we used
   the data that did not include Sargasso and Michigan site data. I presume the other (from
   the CRU web site) were the data used by Phil and Mike Mann that they got from him (where
   exactly did you pick then up from?)and could be the other data set (with those sites
   included). It seems odd that the values are so high in the recent period of this series and
   could conceivably be instrumental data , but would have to check. The scaling of the data
   we used to produce the Crowley curve that formed one of the lines in our spaghetti diagram
   (that we put on the web site under my name and made available to NGDC), was based on taking
   the unscaled composite he sent and re-calibrating against April - Sept. average for land
   North of 20 degrees Lat., and repeating his somewhat bazaar calibration procedure (which
   deliberately omitted the data between 1900-1920 that did not fit with the instrumental data
   (remember his data are also decadal smoothed values). In fact , as we were using summer
   data we calibrated over 1881-1900 (avoiding the high early decades that I still believe are
   biased in summer)  and 1920 - 1960 , whereas he used 1856-1880 and 1920-1965.  Of the
   precise details might differ - but the crux of the matter is that I suspect one of the
   Figures you show may have instrumental data in the recent period - but not ours. If you say
   exactly where these series came from I can ask Tim (who will have done the calibrations) to
   check.
   As  for the second question , the QR data are averaged ring widths from relatively few site
   chronologies in the high north (mostly N.Eurasia - Scandinavia,Yamal,Taimyr), though with a
   few other site data added in as stated. The 2001 data are the MXD data from near 400 sites
   and provide the best interannual to multidecadal indication of summer temps for land areas
   north of 20 degrees than any of the true proxy (ie not including instrumental ) data. No
   idea what the correlation over the common 600 year period is - but I have never said that
   the ring width is anything other than summer temps for the area it covers .
   Keith
   At 20:38 15/07/2005, you wrote:

     Keith,
     Look at the attached. Can you explain to me why these plots
     differ -- particularly after 1880?
     Could you also explain why the Briffa data in QR 2000 are so poorly
     correlated with the Briffa 2001 data?
     I think I know the answers, but I want an independent and spontaneous
     answer from you.
     Thanks,
     Tom.

   --
   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/

