Wednesday, March 28, 2012

2934.txt

cc: k.briffa@uea.ac.uk, valerie.masson@cea.fr, beeratXYZxyzag.ch
date: 15 Nov 2004 13:46:25 -0500
from: Gavin Schmidt <gschmidtatXYZxyzs.nasa.gov>
subject: Re: draft paragraph for PAGES/CLIVAR
to: "Michael E. Mann" <mannatXYZxyzginia.edu>

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
> > 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
> http://www.evsc.virginia.edu/faculty/people/mann.shtml

No comments:

Post a Comment