Monday, December 19, 2011

1140039406.txt

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
All�gaten 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/

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