cc: stefan@pik-potsdam.de
date: Fri, 07 Jan 2005 21:08:55 +0100
from: Stefan Rahmstorf <rahmstorf@pik-potsdam.de>
subject: [Wg1-ar4-ch06] Latest draft 6.2.3
to: IPCC Chapter 6 <wg1-ar4-ch06@joss.ucar.edu>

   Hi friends,
   I've had another go at section 6.2.3, by looking at the three different drafts we had so
   far. Those three drafts did not actually seem to disagree much in substance but more in
   editorial style, each trying to explain more or less the same thing a bit differently.
   I started from my draft here, this being the only one that stuck to the agreed word limit
   (but after including some of your stuff, am slightly over now as well).
   I've closely followed the three points we agreed in Trieste what this section should say,
   sticking to the same order :

     Why models are important to understanding past climate etc.,

     Why paleo is important to understanding realism of models
     Different types of models and uses - refer to other chapters where possible.

   I went through your other drafts piece by piece to check whether they made any important
   points that my draft missed. David and Dick, I would have liked to include all your
   examples (Holocene warm period, mid-Pliocene, greening of Sahara, thermohaline circulation
   etc.) but the word limit is really against this, and it is a methods section rather than
   room many application examples. There are points exclusive to my draft which I wouldn't
   like to drop: that models tend to be developed and tuned with present climate data, so
   testing them on independent data from other climates is important; that a good present
   climate is no test for correct CO2 sensitivity (think of an error in CO2 radiative effect
   calculation, which could still give good present climate but mess up CO2 response); that
   paleoclimate models may use additional components (continental ice sheets, isotopes); that
   mechanistic quantitative understanding is crucial since there are no analogues for the
   future in the past; that we use the same models for past, present and future climate (many
   science journos I talk to believe we have one model doing ice age, another model doing
   present, etc., so this needs to be mentioned in the methods bit).
   If the fact that your draft did leave those out means that you object to them, let me know.
   If anyone thinks anything is unclear or any substance is missing that should be in there,
   let me know. Preferably by returning this draft with the edits you'd like to see (not
   increasing the length...). Otherwise I've chosen the way of presenting things that seemed
   to me to be the most clear and useful to outside people.
   I don't feel this section needs a figure (but if someone has a good one, by all means
   suggest it). Referencing was a bit hard to decide - these are fairly general introductory
   comments on paleoclimate modeling, and adding a zillion refs is probably not called for.
   I've now gone for citing some coupled model examples, where it seemed warranted; help and
   additions welcome. (Nb - EndNote file attached, it has all my Chap6 refs, also for the
   other sections.)
   Sorry for getting upset by the drafts rolling in that did not follow on from what we
   already had for the chapter - I've been working flat out on many things this week despite a
   heavy cold, so I don't react so enthusiastically if things are not moving smoothly.
   Cheers, Stefan

--
Stefan Rahmstorf
[1]www.ozean-klima.de
[2]www.realclimate.org

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