cc: Jonathan Overpeck , Stefan Rahmstorf , Anders Levermann , Eva Bauer , Eystein Jansen , Keith Briffa ,oyvind.paasche@bjerknes.uib.no date: Wed, 15 Feb 2006 16:42:33 +0000 from: Tim Osborn subject: Re: Fwd: Re: Millennium Simulations to: Fortunat Joos ,plattner@climate.unibe.ch Dear all, I have redone all plots for the two alternative baseline periods - see attached PDF. Please look at them on the screen as well as printing them, because with some printers you can hardly see the paler greys and the yellow lines whereas they seem quite bright on my screen. Page 1 is 1500-1899. Page 2 is 1961-1990. Mine and Keith's opinion: 1500-1899 looks better for panels (a), (c) and (d). They look equally as good for panel (c). For panel (e) we are unsure and below are some arguments for and against. [Obviously I can tidy up the 1961-1990 version a bit more, in terms of labelling etc., though it is clearly going to be tricky to find gaps for the key and titles and the vertical scale of panel (d) would need to be changed/extended a bit and then wouldn't match the scale I used for panel (e). So 1961-1990 is a bit harder to get everything looking good and consistent.] At first we thought that the new 1961-1990 version of panel (e) looked better for the reason that there is clearer separation between the "all forcings" (thick lines) and the "natural-only forcings" (thin lines) in the early 20th century. On closer inspection, however, we then were swayed back to the 1500-1899 version of panel (e), because the reason for the clearer separation of the "Nat" and "All" runs in 1961-1990 version is that the stronger solar forcing runs (dark and pale blue and green) are pushed downwards. But pushing them downwards means that during the "Little Ice Age" period these runs (especially the dark and pale blue ones) are clearly in the bottom part of the range of the reconstructions relative to 1961-1990 - and the question is why should we say that the "Nat" runs cannot capture the first phase of 20th century warming when we have started them from cooler conditions, purely on the basis of the amount of warming achieved in the other runs by the time the reference period is reached. This seems harder to defend. It relates back to my earlier comments about (1) using as long a reference period as possible; and (2) thinking about climate changing from the relative stable period, rather than going backwards from the present period with its strong transient changes. Views please? If the decision is made to go with 1961-1990, then Keith suggests sticking with 1500-1899 for panels (a)-(d) as before, and make the new EMIC runs (currently panel (e)) into a stand-alone figure with 1961-1990 baseline. Views required urgently! Cheers Tim Attachment Converted: "c:\eudora\attach\modelsA-E_2versions.pdf" Dr Timothy J Osborn Climatic Research Unit School of Environmental Sciences, University of East Anglia Norwich NR4 7TJ, UK e-mail: t.osborn@uea.ac.uk phone: +44 1603 592089 fax: +44 1603 507784 web: http://www.cru.uea.ac.uk/~timo/ sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm