Saturday, June 2, 2012

4844.txt

cc: k.briffa@uea.ac.uk, valerie.masson@cea.fr, beeratXYZxyzag.ch
date: Mon, 15 Nov 2004 15:50:29 -0500
from: "Michael E. Mann" <mannatXYZxyzginia.edu>
subject: Re: draft paragraph for PAGES/CLIVAR
to: Val�rie Masson-Delmotte <Valerie.MassonatXYZxyz.fr>, "Gavin Schmidt" <gschmidtatXYZxyzs.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, Val�rie 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: mannatXYZxyzginia.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: mannatXYZxyzginia.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: mannatXYZxyzginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137
[3]http://www.evsc.virginia.edu/faculty/people/mann.shtml

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