From	Stefan Rahmstorf	Date	Tue, 26 Jul 2005 12:09:33 +0200
To	Keith Briffa
CC	wg1-ar4-ch06@joss.ucar.edu, Jonathan T. Overpeck, Eystein Jansen
Subject	Last Millennium section 6.5 - comments by SR
Hi Keith and all, (please everyone have a look at point (4)) I think section 6.5 is in remarkably good shape (certainly compared to my own..). There are some comments from me: (1) About the new proxy reconstructions, the section says: "Most of these are shown..." in the Figure. This immediately raises the question: why not all? Which one is not shown? This section will be scrutinised with great suspicion by some people, so we need to be careful. Can you clarify which one you left out, and why? Or can we just write: "These are shown..." That would be much nicer. (2) Several times you say "simply scaled" - would "scaled" do as well? The "simply" in this context sounds a bit like we criticise that. (3) Is "predictand" a word that everybody knows? I'd never seen it before. (4) Now here is my biggest question, that I think we need to discuss in the whole group. Figure 6.5.2-1 shows simulations of the past millennium, relative to 1500-1899 means. Is this really the best reference period? Contra: it differs from how we show the data reconstructions, i.e., relative to 1961-1990. Everyone knows what that climate actually was, since there are good instrumental data for 1961-1990, so that it makes sense to look at changes relative to that period. Nobody knows what the real 1500-1899 mean was, so this is a fictitious baseline. Pro: it gets rid of "end effects", i.e. model initialisation problems at the beginning (as in Von Storch 04), and different anthropogenic forcings used at the end (e.g. some ignore aerosols); the simulations look closer together in this way (right?) I have not formed a clear opinion on what is best. (5) Also on the figures: I like the grey bands, but here's a suggestion for improvement: instead of leaving the core region between those two bands white, I think they should also be shaded - either the same grey, or a darker shade of grey. This makes it more clear that we are talking about one, wide uncertainty band here, not about two seperate things. It had me confused at first when I saw it, even though I was there when we discussed this in Beijing. Final point: we need to keep an eye on developments concerning the model tests of the proxy method, there seem to be several important things in the pipeline there. Cheers, Stefan -- To reach me directly please use: [1]rahmstorf@ozean-klima.de (My former addresses @pik-potsdam.de are read by my assistant Brigitta.) Stefan Rahmstorf [2]www.ozean-klima.de [3]www.realclimate.org References 1. mailto:rahmstorf@ozean-klima.de 2. http://www.ozean-klima.de/ 3. http://www.realclimate.org/