From	Jonathan T. Overpeck	Date	Wed, 5 Jan 2005 12:24:47 -0700
To	Keith Briffa
CC	Eystein Jansen, cddhr@giss.nasa.gov, Fortunat Joos, Fortunat Joos, Ricardo Villalba
Subject	Re: Fwd: Re: [Wg1-ar4-ch06] IPCC last 2000 years data
Hi Keith and Co - I think David likes a good debates, so the main thing is to consider his comments and respond appropriately. Although the first priority has to be on the ZOD text and display items, maybe you can go back over his comments AFTER the looming deadline and further discuss things with David and others. For now, just work away. The biggest issue is how to handle forcing and simulations - i.e., where to put different pieces in the chapter. Eystein and I will help the team work through this. More soon, but for now just proceed as you have been proceeding. There is real merit to the concept that your section is about how climate varied over the last 2ka, and what caused these variations. The flip side is that we need to get a clear vision of how this differs from what goes into the other sections. Eystein and I will work more on this asap. Your plan re: glaciers is good. That's a tough one, but it has to be boiled WAY down. Moreover, my gut is to focus on the extent to which these complicated natural archives (e.g., complicated by ppt change) support or do not support the other proxy evidence/conclusions. This is why I was thinking we might think about a box, and to include the Lonnie perspective in it - e.g., glaciers are now melting everywhere (almost - we know why they are not in those places) in a manner unprecedented in the last xxxx years. Make sense? See what Olga says, and if needbe, I can help focus that stuff more. Thanks! Peck >Hi Peck (et al) >I am considering comments (including David's) re last 2000 years - >some are valid = some are not . Will try to chop out bits but we >need this consensus re the forcing and responses bit - I am for >keeping the forcings in as much as they relate to the specific model >runs done - and results for last 1000 years as I suspect that they >will not be covered in the same way elsewhere . David makes couple >good points - but extent to which forcings different (or >implementation) perhaps need addressing here. The basic agreement I >mean is that the recent warming is generally unprecedented in these >simulations. >It will take time and input from the tropical ice core /coral people >to do the regional stuff well . I think the glaciological stuff is a >real problem - other than just showing recent glacial states (also >covered elsewhere) - of course difficult to interpret any past >records without modelling responses (as in borehole data), but this >requires considerable space . My executive decision would be to ask >Olga to try to write a couple of papragraphs on limits of >interpretation for inferring precisely timed global temperature >changes? What do others think? I only heaved Olga's stuff in at >last moment rather than not include it - but of course it needs >considerable shortening. The discussion of tree-ring stuff is >problematic because it requires papers to be published eg direct >criticism of Esper et al. We surely do not want to waste space HERE >going into this esoteric topic? All points on seasonality , I agree >with , but the explicit stuff on M+M re hockey stick - where is >this? ie the bit about normalisation base affecting redness in >reconstructions - sounds nonsense to me ? > >I have to consider the comments in detail but am happy for hard >direction re space and focus. If concensus is no forcings and model >results here fine with me - Peck and Eystein to rule >Keith > -- 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/