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" <mann@virginia.edu>
subject: Re: draft paragraph for PAGES/CLIVAR
to: Valrie Masson-Delmotte <Valerie.Masson@cea.fr>, "Gavin Schmidt" <gschmidt@giss.nasa.gov>

   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, Valrie 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

