cc: "Stefan Rahmstorf" , "Valerie Masson-Delmotte" , "Eystein Jansen" , "Keith Briffa" date: Sat, 7 Apr 2007 19:03:44 +0100 (BST) from: K.Briffa@uea.ac.uk subject: Re: urgent help re Augusto Mangini to: "Jonathan Overpeck" Hi all as for the last 1300 years - the Moberg paper included some speleothem data but the trouble is that they are not absolutely dated and the calibration issues are far from settled - ie there are not the level of detaled process studies that establish the dominance of temperature control for many individual speleohem records (the 18O data represent a mixture of temperature annd precipitation behaviour, mixed with varying water residence times and ambiguities caused by cave ventilation changes and CO2 concentrations - often these effects are non linearly transfered) as is shown for other proxies. One paper that attempts to do a "large scale " study using spelethems from Scotland , Austria etc (BY CLAIRE SMITH ET AL.)shows an amplitude of variation that is not in any way in contradiction to the general envelope we show - but even here they have breaks in the record which make the scaling (in terms of temperture ) very uncertain in the early part of the record. The one study in the Alps that shows a warm medieval period , was not in my opinion , robustly calibrated . The bottom line is THE DATING UNCERTAINTY AND POORLY UNDERSTOOD FORCING PROCESSES AND THE WEAK CALIBRATION STRENGTH AT HIGH TO MEDIUM FREQUENCIES MEANS THAT THEY COULD NOT BE GIVEN MUCH EMPHASIS AT PRESENT .I am at home and doing this from memory but later I am happy to defend thee statements by references to speleothem literature. cheers Keith > Hi Stefan - Valerie was the lead on the Holocene section, so I'll cc > her. I agree that your approach is the smart one - it's easy to show > proxy records (e.g., speleothems) from a few sites that suggest > greater warmth than present at times in the past, but our assessment > was that there wasn't a period of GLOBAL warmth comparable to > present. We used the term likely, however, since there still is a > good deal of work to do on this topic - we need a better global > network of sites. > > Keith can comment on the last 1300 years, but again, I think there is > no published evidence to refute what we assessed in the chapter. > Again, one or two records does not hemispheric or global make. > > I think Keith or Valerie could comment further if they're not > Eastering. Eystein, likewise might have something, but I think it is > his national responsibility to hit the glaciers over Easter. > > Best, Peck > > >>Dear Peck and IPCC coauthors, >> >>- I know it's Easter, but I'm having to deal with Augusto Mangini, a >>German colleague who has just written an article calling the IPCC >>paleo chapter "wrong", claiming it has been warmer in the Holocene >>than now, and stalagmites show much larger temperature variations >>than tree rings but IPCC ignores them. What should I answer? >> >>One of my points is that IPCC shows all published large-scale proxy >>reconstructions but there simply is none using stalagmites - so >>please tell me if this is true?!! My main point will be the local >>vs hemispheric issue, saying that Mangini only provides local >>examples, while the IPCC statement is about hemispheric or global >>averages. >> >>But how about local variations - do stalagmites show much larger >>ones than tree rings? Any suggestions what other counter-arguments I >>could write? Do we have a stalagmite expert on the author team, >>other than contributing >>author Dominik Fleitmann, whom I've already identified? >>I have to submit my response to the newspaper tomorrow. >> >>Thanks, Stefan >> >>-- >>Stefan Rahmstorf >>www.ozean-klima.de >>www.realclimate.org >> >> >> >> >>-- >>Stefan Rahmstorf >>www.ozean-klima.de >>www.realclimate.org > > > -- > 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/ >