cc: Eystein Jansen
date: Wed, 15 Feb 2006 11:57:07 -0700
from: Jonathan Overpeck
subject: Bullet debate number 2
to: Keith Briffa
Hi again - as for bullet issue number 2, I agree that we don't need to go with the suggest
stuff on solar/forcing, BUT, I agree w/ Susan that we should try to put more in the bullet
about "Subsequent evidence" Would you pls send a new bullet that has your suggested changes
below, and that includes something like:
"Subsequent evidence, including x, y and z, reinforces this conclusion." Need to convince
readers that there really has been an increase in knowledge - more evidence. What is it?
The bullet can be longer if needed.
Simply make "1000" "1300 years. " and delete "and unusually warm compared with the
last 2000 years."
It is certainly NOT our job to be discussing attribution in the 20th century - this is
Chapter 9 - and we had no room (or any published material) to allow a discussion of
relative forcing contributions in earlier time. Therefore a vague statement about
"perhaps due to solar forcing" seems unjustified.
I suggest this should be
Taken together , the sparse evidence of Southern Hemisphere temperatures prior to the
period of instrumental records indicates that overall warming has occurred during the
last 350 years, but the even fewer longer regional records indicate earlier periods that
are as warm, or warmer than, 20th century means.
fine , though perhaps "warmth" instead of "warming"?
and need to see EMIC text
Peck, you have to consider that since the TAR , there has been a lot of argument re
"hockey stick" and the real independence of the inputs to most subsequent analyses is
minimal. True, there have been many different techniques used to aggregate and scale
data - but the efficacy of these is still far from established. We should be careful not
to push the conclusions beyond what we can securely justify - and this is not much other
than a confirmation of the general conclusions of the TAR . We must resist being pushed
to present the results such that we will be accused of bias - hence no need to attack
Moberg . Just need to show the "most likely"course of temperatures over the last 1300
years - which we do well I think. Strong confirmation of TAR is a good result, given
that we discuss uncertainty and base it on more data. Let us not try to over egg the
For what it worth , the above comments are my (honestly long considered) views - and I
would not be happy to go further . Of course this discussion now needs to go to the
wider Chapter authorship, but do not let Susan (or Mike [Mann]) push you (us) beyond where we
know is right.
Professor Keith Briffa,
Climatic Research Unit
University of East Anglia
Norwich, NR4 7TJ, U.K.
Jonathan T. Overpeck
Director, Institute for the Study of Planet Earth
Professor, Department of Geosciences
Professor, Department of Atmospheric Sciences
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