cc: Hans.von.Storch@gkss.de, Eduardo.ZoritaatXYZxyzs.de
date: Wed Jan 5 15:03:17 2005
from: Keith Briffa <k.briffaatXYZxyz.ac.uk>
subject: Re: Mike Mann's claims
to: Hans.von.Storch@gkss.de, masatXYZxyz.dk
I can only think that these comments relate to my suggestion (made to Mike and others at a
recent CLIVAR/PAGES meeting in Canada) that we ( ie those interested parties) need to
organise a well formulated co-operative experiment , where the same data sets can be used
to run a series of controlled comparisons of different calibration techniques.
In discussing the results of the your work and earlier attempts to use the ORIGINAL Mann et
al 1998,1999 techniques (by Eduardo and Irene ) I commented that we could still not be sure
that the methods were being applied in the same way.
Mike's more recent spatial transfer function work (Rutherford et al ) - on which Tim and I
are co-authors , compared a different technique than he originally used , with our approach
(based on local aggregation of chronologies and simple regression to produce regional
reconstructions , which were then used in a PC regression to produce a NH series). These
give similar results as regards NH land summer temperatures. This paper predates your
Science piece. As we (Tim and I) believe the local calibration and aggregation approach is
very likely to lead to underestimation of long-timescale variance in the larger (NH)
series , we believed it a logical conclusion that Mike's approach did so also. You then
published your paper demonstrating that his original approach likely does just that.
However, Mike has apparently shown that his NEW method , when used with pseudo proxies and
a different climate model does NOT lose the low-frequency. He showed some results briefly
in Canada that seemed to demonstrate this - but incidentally, DID seem to lose the high
frequency extreme variability. I have NOT read this paper , which I believe is in review
(NOT BY ME). Mike did not , however, use his original technique (that you purportedly
follow in your Science piece, though others (not sure who ) that he is working with might
be doing this.
However the new Mann method DOES seem to produce the same NH curve as the original method.
Hence an apparent contradiction . Hence my belief that the different methods should be used
, with the same data (and targets) in a much more systematic way, to see how they compare.
This experiment should include the use of the same simulated data also.
Tim and I have commented (in our perspective piece) that the loss of long-timescale
amplitude in the NH history might be exaggerated by the results of your use of the ECHO G
simulation - as this may produce too large an amplitude in the first place (for different
reasons) and so the question of how great the underestimation in the Mann original NH
reconstruction is in real life is still a moot point - and hence the real need to set up
this controlled test using the alternative simulations, methods.
I have nothing in press other than the Rutherford paper and have said nothing other than
I would like to set up the comparative exercise - as part of SOAP perhaps - but with the
of Mike and his colleagues if they are willing.
Hope we can discuss this at the next SOAP meeting
At 18:34 04/01/2005, Hans.von.StorchatXYZxyzs.de wrote:
Dear Martin, dear Keith,
Mike Mann has made the following claims:
"You should be aware that a comment is in press in "Science" casting significant doubt
on the claims of Von Storch and Zorita, and another paper, in review, suggests that
their conclusions are incorrect, . A 3rd paper, by the Danish Meteorological Institute
(DMI) group using the same model as von Storch, cannot reproduce the von Stroch results
(they find much less variability than von Storch), suggesting that their were some
serious problems with the von Storch simulation as well as with their analysis of the
simulation results. I would suggest that you get in touch with these individuals (e.g.
Keith Briffa: k.briffaatXYZxyz.ac.uk or Martin Stendel: firstname.lastname@example.org) for a more balanced view
of the Von Storch claims."
May I ask you to verify this statement and, if true, send us a copy of your papers? And,
possibly, explain your "more balanced views"?
All the best
Hans von Storch
Institute for Coastal Research, GKSS Research Center
Max-Planck-Strasse 1, 21502 GEESTHACHT, Germany
ph: +49 4152 87 1831, fx: +49 4152 87 2832
mobile: + 49 171 212 2046
Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.