cc: k.briffa@uea.ac.uk, valerie.masson@cea.fr, beer@eawag.ch date: Mon, 15 Nov 2004 15:50:29 -0500 from: "Michael E. Mann" subject: Re: draft paragraph for PAGES/CLIVAR to: Valérie Masson-Delmotte , "Gavin Schmidt" Thanks Valerie, Yes, I agree--it could be tough to agree upon the forcings as a community, but something to strive for in any case I suppose. sorry to hear of Elsa's scare. Flight home wasn't too bad, but it was a "red eye" and I didn't get much sleep that night. Then I had to teach and host a speaker (Judith Lean) well into the evening. I was exhausted. But fortunately Judith's visit was enjoyable. I slept about 24 hours after that! cheers, mike At 03:38 PM 11/15/2004, Valérie Masson-Delmotte wrote: Hello, The text is OK for me. I guess that the intercomparison of forcings is going to be maybe more difficult than the intercomparison of model results... I hope you had good travel conditions back home. We had a last laugh in Paris where it appeared that Elsa's luggage had been lost somewhere in Heathrow... Valerie. > mostly fine. However, in expanding from the point I tried to make in BC, > it is extremely unlikely that everyone will (or will be able to) do the > same experiments with the same forcings. Maybe more useful would be to > acknowledge that different groups will use whatever they feel is best > (for various reasons), but that it is made clear what those forcings are > (so that people can estimate what effect a different set of forcings > would have done). > > Gavin > > On Mon, 2004-11-15 at 12:11, Michael E. Mann wrote: >> sorry, one slight revisions (I added on one sentence at the end to >> specifically address the two bulleted points that were listed with >> this item). >> >> Climate Variability over the Last Few Millennia >> >> Proxy reconstructions and model simulations both suggest that late >> 20th century warmth is anomalous in the context of the past 1000-2000 >> years. Significant differences exist, however, between various >> competing estimates. Some differences between estimated extratropical >> and full (combined tropical and extratropical) hemispheric mean >> temperature changes in past centuries may be consistent with seasonal >> and spatially-specific responses to climate forcing. Forced changes in >> large-scale atmospheric circulation such as the NAO, and internal >> dynamics related to El Nino, may play an important role in explaining >> regional patterns of variability and change in past centuries. >> Despite progress in recent years, important uncertainties and caveats >> exist, however, with regard to both empirical reconstructions and >> model estimates. One important issue relates to the varying >> seasonality and spatial representativeness of competing estimates. >> Another important issue involves the reliability of the statistical >> methodologies used for proxy-based climate reconstruction, including >> potential extensions back in time. Such methodologies have been >> tested using a long forced simulation of coupled climate models. >> Multiple such analyses, however, come to conflicting conclusions with >> regard to the likely fidelity of current methods used in proxy-based >> climate reconstruction. An additional important issue involves the >> reliability of estimates of past climate forcing used to drive >> simulations of climate change over the past millennium or longer. >> Dramatically different estimates of volcanic and solar radiative >> forcing, in particular, have been used in various different >> simulations, making a direct comparison among simulations difficult. >> We encourage the scientific community to work towards adopting a >> standard protocol for such simulations, including consensus estimates >> of various radiative forcing estimates, and in the case of coupled >> model simulations, the use of appropriate ensembles of simulations >> over the past few millennia. >> >> At 12:00 PM 11/15/2004, Michael E. Mann wrote: >> > Dear Keith, Valerie, Juerg, and Gavin, >> > >> > First, I wanted to say that I enjoyed seeing and talking with each >> > of you last week at the working group meeting. Looking forward to >> > more of these get togethers in the future. >> > >> > I was asked to write a paragraph on the key scientific issues and >> > questions related to the topic "Climate Variability over the last >> > few millennia". Each of your names was also listed. So I've drafted >> > a paragraph, and would like to get your suggestions. I'd like to >> > submit this Friday, so please get back to me before then. If I don't >> > hear from you by then, I'll assume you're ok w/ the current >> > wording... >> > >> > Thanks in advance for your help, >> > >> > mike >> > >> > Climate Variability over the Last Few Millennia >> > >> > Proxy reconstructions and model simulations both suggest that late >> > 20th century warmth is anomalous in the context of the past >> > 1000-2000 years. Significant differences exist, however, between >> > various competing estimates. Some differences between estimated >> > extratropical and full (combined tropical and extratropical) >> > hemispheric mean temperature changes in past centuries may be >> > consistent with seasonal and spatially-specific responses to climate >> > forcing. Forced changes in large-scale atmospheric circulation such >> > as the NAO, and internal dynamics related to El Nino, may play an >> > important role in explaining regional patterns of variability and >> > change in past centuries. Despite progress in recent years, >> > important uncertainties and caveats exist, however, with regard to >> > both empirical reconstructions and model estimates. One important >> > issue relates to the varying seasonality and spatial >> > representativeness of competing estimates. Another important issue >> > involves the reliability of the statistical methodologies used for >> > proxy-based climate reconstruction including potential extensions >> > back in time. Such methodologies have been tested using a long >> > forced simulation of coupled climate models. Multiple such analyses, >> > however, come to conflicting conclusions with regard to the likely >> > fidelity of current methods used in proxy-based climate >> > reconstruction. An additional important issue involves the >> > reliability of estimates of past climate forcing used to drive >> > simulations of climate change over the past millennium or longer. >> > Dramatically different estimates of volcanic and solar radiative >> > forcing, in particular, have been used in various different >> > simulations, making a direct comparison among simulations difficult. >> > >> > ______________________________________________________________ >> > Professor Michael E. Mann >> > Department of Environmental Sciences, Clark Hall >> > University of Virginia >> > Charlottesville, VA 22903 >> > _______________________________________________________________________ >> > e-mail: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) >> > 982-2137 >> > [1]http://www.evsc.virginia.edu/faculty/people/mann.shtml >> ______________________________________________________________ >> Professor Michael E. Mann >> Department of Environmental Sciences, Clark Hall >> University of Virginia >> Charlottesville, VA 22903 >> _______________________________________________________________________ >> e-mail: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) >> 982-2137 >> [2]http://www.evsc.virginia.edu/faculty/people/mann.shtml > -- Valerie. ____________________________________________________________________________ Laboratoire des Sciences du Climat et de l'Environnement (UMR CEA/CNRS 1572) Bat 701, L'Orme des Merisiers CEA Saclay, 91 191 Gif-sur-Yvette cedex , France Tel. (33) 1 69 08 77 15, Fax. (33) 1 69 08 77 16 ______________________________________________________________ Professor Michael E. Mann Department of Environmental Sciences, Clark Hall University of Virginia Charlottesville, VA 22903 _______________________________________________________________________ e-mail: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137 [3]http://www.evsc.virginia.edu/faculty/people/mann.shtml