From: Jonathan Overpeck <jto@u.arizona.edu>
To: Eystein Jansen <Eystein.Jansen@geo.uib.no>
Subject: Re: Bullet debate number 2
Date: Wed, 15 Feb 2006 16:36:46 -0700
Cc: Keith Briffa <k.briffa@uea.ac.uk>

   thanks. Agree on the attribution front, but what about being more specific (at least a
   little) about what the "subsequent evidence" is. Is there really anything new that gives us
   more confidence?

   Keith? Eystein?

   thx, peck

     Hi,

     I think this version of bullett two is best:

     o       The TAR pointed to the "exceptional warmth of the late 20th century, relative to
     the past 1000 years". Subsequent evidence reinforces this conclusion. Indeed, it is very
     likely that average Northern Hemisphere temperatures during the second half of the 20th
     century were warmer than any other 50-year period in the last 500 years. It is also
     likely that this was the warmest period in the past 1300 years . The uneven coverage and
     characteristics of the proxy data mean that these conclusions are most robust over
     summer, extra-tropical, land areas.

     I agree with Keith we cannot enter into the attibution aspects that Susan alludes to.

     Eystein

     At 11:57 -0700 15-02-06, Jonathan Overpeck wrote:

     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.

     Thanks, Peck

     Second
     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.
     Third
     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.
     Fourth
     fine , though perhaps "warmth" instead of "warming"?
     and need to see EMIC text
     Fifth
     suggest delete
     Sixth
     suggest delete
     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
     pudding.
     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) push you (us) beyond where we
     know is right.
     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.
     Phone: +44-1603-593909
     Fax: +44-1603-507784
     http://www.cru.uea.ac.uk/cru/people/briffa/

     --

     Jonathan T. Overpeck
     Director, Institute for the Study of Planet Earth
     Professor, Department of Geosciences
     Professor, Department of Atmospheric Sciences
     Mail and Fedex Address:

     Institute for the Study of Planet Earth
     715 N. Park Ave. 2nd Floor
     University of Arizona
     Tucson, AZ 85721
     direct tel: +1 520 622-9065
     fax: +1 520 792-8795
     http://www.geo.arizona.edu/
     http://www.ispe.arizona.edu/

     --

     ______________________________________________________________
     Eystein Jansen
     Professor/Director
     Bjerknes Centre for Climate Research and
     Dep. of Earth Science, Univ. of Bergen
     Allégaten 55
     N-5007 Bergen
     NORWAY
     e-mail: eystein.jansen@geo.uib.no
     Phone:    +47-55-583491  -  Home: +47-55-910661
     Fax:       +47-55-584330

--

   Jonathan T. Overpeck
   Director, Institute for the Study of Planet Earth
   Professor, Department of Geosciences
   Professor, Department of Atmospheric Sciences
   Mail and Fedex Address:
   Institute for the Study of Planet Earth
   715 N. Park Ave. 2nd Floor
   University of Arizona
   Tucson, AZ 85721
   direct tel: +1 520 622-9065
   fax: +1 520 792-8795
   http://www.geo.arizona.edu/
   http://www.ispe.arizona.edu/

