From: David Rind <drind@giss.nasa.gov>
To: Jonathan Overpeck <jto@u.arizona.edu>
Subject: Re:
Date: Wed, 13 Sep 2006 16:43:08 -0400
Cc: Keith Briffa <k.briffa@uea.ac.uk>, rahmstorf@ozean-klima.de, Bette Otto-Bleisner <ottobli@ncar.ucar.edu>, cddhr@giss.nasa.gov, joos <joos@climate.unibe.ch>, Eystein Jansen <eystein.jansen@geo.uib.no>, "Ricardo Villalba" <ricardo@lab.cricyt.edu.ar>, t.osborn@uea.ac.uk

   Leaving aside for the moment the resolution issue, the statement should at least be
   consistent with our figures. Fig. 6-10 looks like there were years around 1000 AD that
   could have been just as warm  - if one wants to make this statement, one needs to expand
   the vertical scale in Fig. 6-10 to show that the current warm period is 'warmer'.

   Now getting back to the resolution issue: given what we know about the ability to
   reconstruct global or NH temperatures in the past - could we really in good conscience say
   we have the precision from tree rings and the very sparse other data to make any definitive
   statement of this nature (let alone accuracy)? While I appreciate the cleverness of the
   second sentence, the problem is everybody will recognize that we are 'being clever' - at
   what point does one come out looking aggressively defensive?

    I agree that leaving the first sentence as the only sentence suggests that one is somehow
   doubting the significance of the recent warm years, which is probably not something we want
   to do. What I would suggest is to forget about making 'one year' assessments; what Fig.
   6-10 shows is that the recent warm period is highly anomalous with respect to the record of
   the last 1000 years. That would be what I think we can safely conclude the last 1000 years
   really tells us.

   David

   At 9:10 AM -0600 9/13/06, Jonathan Overpeck wrote:

     Keith - thanks for this and the earlier updates. Stefan is not around this week, but
     hopefully the others on this email can weight in. My thoughts...

     1) We MUST say something about individual years (and by extension the 1998 TAR
     statement) - do we support it, or not, and why.

     2) a paragraph would be nice, but I doubt we can do that, so..

     3) I suggest putting the first sentence that Keith provides below as the last sentence,
     in the last (summary) para of 6.6.1.1. To make a stand alone para seems like a bad way
     to end the very meaty section.

     4) I think the second sentence could be more controversial - I don't think our team
     feels it is valid to say, as they did in TAR, that "It is also likely that, in the
     Northern Hemisphere,... 1998 was the warmest year" in the last 1000 years. But, it you
     think about it for a while, Keith has come up with a clever 2nd sentence (when you
     insert "Northern Hemisphere" language as I suggest below). At first, my reaction was
     leave it out, but it grows on you, especially if you acknowledge that many readers will
     want more explicit prose on the 1998 (2005) issue.

     Greater uncertainty associated with proxy-based temperature estimates for individual
     years means that it is more difficult to gauge the significance, or precedence, of the
     extreme warm years observed in the recent instrumental record. However, there is no new
     evidence to challenge the statement made in the TAR that 1998 (or the subsequent
     near-equivalent 2005) was likely the warmest of Northern Hemisphere year over the last
     1000 years.

     5) I strongly agree we can't add anything to the Exec Summary.

     6) so, if no one disagrees or edits, I suggest we insert the above 2 sentences to end
     the last (summary) para of 6.6.1.1. Or should we make it a separate, last para - see
     point #3 above why I don't favor that idea as much. But, it's not a clear cut issue.

     Thoughts? Thanks all, Peck

     Eystein and Peck
     I have thought about this and spent some time discussing it with Tim. I have come up
     with the following

     Greater uncertainty associated with proxy-based temperature estimates for individual
     years means that it is more difficult to gauge the significance, or precedence, of the
     extreme warm years observed in the recent instrumental record. However, there is no new
     evidence to challenge the statement made in the TAR that 1998 (or the subsequent
     near-equivalent 2005) was likely the warmest in the last 1000 years.

     This should best go after the paragraph that concludes section 6.6.1.1
     I believe we might best omit the second sentence of the suggested new paragraph - but
     you might consider this too subtle (or negative) then. I think the second sentence is
     very subtle also though - because it does not exclude the possibility that the same old
     evidence that challenges the veracity of the TAR statement exists now , as then!
     I think this could go in the text where suggested , but I think it best NOT to have a
     bullet about this point.We need to check exactly what was saidin the TAR . Perhaps a
     reference to the Academy Report could also be inserted here?
     Anyway, you asked for a straw-man statement for all to argue about so I suggest we send
     this to Stefan, David , Betty and whoever else you think.
     cheers
     Keith

     --
     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
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