From: Jonathan Overpeck <jto@u.arizona.edu>
To: Henry Pollack <hpollack@umich.edu>
Subject: Re: Huang, et al GRL 24, 1997
Date: Tue, 18 Jul 2006 21:50:19 -0600
Cc: Eystein Jansen <eystein.jansen@geo.uib.no>, Valerie Masson-Delmotte <Valerie.Masson@cea.fr>, t.osborn@uea.ac.uk, Keith Briffa <k.briffa@uea.ac.uk>, "Ricardo Villalba" <ricardo@lab.cricyt.edu.ar>

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Hi Henry - excellent feedback, thanks. I think it 
should be easy for Valerie (Holocene issues in 
6.5) and Keith/Tim.Ricardo (last 2k, section 6.6) 
to deal with the 'expert' review issues regarding 
this paper. It sounds to me like that is the 
place for discussion of this paper, rather than 
in the text itself. BUT, it is important that the 
responses to review comments be thorough and 
convincing - Valerie and Keith - please update 
your responses in this respect.

thanks all, Peck


>Hi Peck and others,
>
>Attached is a brief discussion of the subject 
>paper and the questions you have asked me to 
>address. Let me know if you need additional 
>clarification.
>
>Cheers,
>Henry
>
>  ___    ___    Henry N. Pollack
>[   \  /   ]   Professor of Geophysics
>  |   \/   |    Department of Geological Sciences
>  |MICHIGAN|    University of Michigan
>[___]\/[___]   Ann Arbor, Michigan 48109-1005, U.S.A.
>
>  Phone: 734-763-0084   FAX: 734-763-4690
>  e-mail: hpollack@umich.edu
>  URL:  www.geo.lsa.umich.edu/~hpollack/
>  URL:  www-personal.umich.edu/~hpollack/book.html
>
>
>Quoting Jonathan Overpeck <jto@u.arizona.edu>:
>
>>Hi again Henry - I've attached an 1997 paper of 
>>your's and wonder if you could shed some 
>>up-to-date insights on how to best interpret. 
>>In particular:
>>
>>1) it has been pointed out to us that the 
>>result in this paper argue for a globally warm 
>>period during the middle Holocene that was 
>>warmer than today. Our assessment (i.e., Figure 
>>6.9) indicates that there was likely no period 
>>during the Holocene that was warmer around the 
>>global than the late 20th century. Especially 
>>outside of the tropics, there were periods 
>>warmer than today during the Holocene, but 
>>these regionally warm periods were not 
>>synchronous - at least at the centennial scale 
>>we can examine with proxy data. Thus, although 
>>Huang et al. 1997, indicates greater mean 
>>annual global warmth, it was unlike the 
>>synchronous global warming of the late 20th 
>>century.
>>
>>Plus, we believe the warmth of the Holocene was 
>>driven by orbital forcing, and that what we see 
>>makes sense in that regard. Huang et al, 1997 
>>can be explained perhaps (this is a question) 
>>by the heavy borehole coverage in the Northern 
>>mid- to high-latitudes? We also know that proxy 
>>data shown in Fig 6.9 also indicate more 
>>warming (again, not synchronous) in Southern 
>>Hem mid-latitudes - where there are also many 
>>boreholes.
>>
>>Obviously, another issue is that the boreholes 
>>don't give the same temporal resolution as the 
>>other proxy records we synthesized/assessed, 
>>and at least in your paper, there isn't 
>>regional information either.
>>
>>So - the point is not (unless you suggest 
>>otherwise) that Huang et al 97 is wrong, but 
>>rather than within the limits of the data, it 
>>is compatible with what the higher-resolution, 
>>regionally-specific, multi-proxy data are 
>>showing in Fig 6.9, and that there was likely 
>>no period during the Holocene that was warmer 
>>synchronously around the global than the during 
>>the late 20th century. Do you agree with this, 
>>and is our reasoning accurate and complete?
>>
>>2) Huang et al 1997 also shows evidence for 
>>warmth within the last 500-1000 years that was 
>>greater than during the 20th century AND a cool 
>>minima 200 years ago. Both of these are 
>>highlighted in your abstract, and both seem 
>>incompatible with other evidence. For example, 
>>your own more recent work has shown the coolest 
>>temperatures to be about 500 years ago.
>>
>>We didn't think it was within our focus to 
>>comment on these issues, but we are being asked 
>>to by reviewers, and it would be good to have 
>>your help in addressing these issues - 
>>hopefully in our responses to review comments 
>>rather than in our main text (which has to be 
>>shortened).
>>
>>Many thanks for your help with this paper and the issues it raises.
>>
>>Best, Peck
>>
>>
>>
>>--
>>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/
>
>
>
>
>Attachment converted: Macintosh HD:GRL 1997.doc (WDBN/«IC») (00141CBF)


-- 
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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