Wednesday, January 18, 2012


cc: Eystein Jansen <>,,, Valerie Masson-Delmotte <>, joos <>
date: Thu, 13 Jan 2005 11:05:09 -0700
from: Jonathan Overpeck <>
subject: comments for and 6.5.6
to:, Keith Briffa <>

All - I guess it is David's job to lead the incorporation of these comments into these two
sections which he leads, but others may want to discuss too.

What do you think about a general bullet along the lines of

Commonly cited warm periods, including the Medieval Warm Period, Holocene Climate Optimum,
Altithermal, Hypsithermal and others appear to have been distinct only regionally, and in
a time-transgressive manner. They should not be cited as globally warm intervals comparable
to the late 20th century, and are usually too poorly defined to be of use in the

There will soon be a box on the Medieval Warm Period that makes this case for the MWP. Tim
and Keith - when drafting, perhaps you should change the box's emphasis slightly to include
these other periods. Title it "Box 6.1: The Medieval Warm Period and other Poorly Defined
Periods of Regional Warmth." Use the MWP as the in-depth example, and then we can mention
the other terms only in the intro. After the ZOD, we can make sure we got it all perfect.

Lets put an end to some myths that have been around longer than we have!

Thanks all, especially David for updating these two sections as appropriate.

cheers, peck

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Date: Thu, 13 Jan 2005 16:19:31 +0000
To: Jonathan Overpeck <>,
Keith Briffa <>
From: Tim Osborn <>
Subject: Re: Need your help on something important
Cc: Eystein Jansen <>,,,
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At 23:50 12/01/2005, Jonathan Overpeck wrote:

Toward that end, I wonder if you two (or maybe just Tim if Keith is working more on could read and comment/edit on:
Section -evaluation of transient model runs of the last millennium
Section 6.5.8 - synthesis of climate sensitivity issues
Eystein and I are asking that you do this FAST because these sections must be compatible
with your section (and because you guys know as much as any about the material
in these two other sections!).

Dear Peck (plus cc to others - have I sent it to the appropriate people?),
Keith and I have looked at these sections and the attached documents contain my tracked
changes. They seem to be compatible with Keith's section and the figures. We've put in
a couple of simple cross-references to the figures from Keith's section. Plus some
minor changes. Plus some comments, particularly about the section(d) of the climate
sensitivity section. Keith expands upon these latter comments with the following:
It would be wise NOT to refer to the Maunder Minimum time period. Anyway, 1675-1715 is
(by most opinions) the LATE Maunder Minimum (an accidental name that derives from the
random non-availability of documentary/paleo data for the earlier part of the period in
some [Swiss] study by Pfister and people). Up to then, MM was taken to be 1645/50 to
1715. By using this terminology you divert objective analysis of TOTAL forcing change
(particularly given volcanic uncertainty).
The definition of "today" is also crucial as it affects (albeit not precise) estimation
of forcing changes from the earlier period. The wider the comparison base, the more
imprecise the estimates. The narrower the base, the more you could argue about likely
non-equilibrium (see Tim's comment in attached document).
The volcanic forcing likely means that the LMM is likely not in equilibrium either!
Nice if base period for estimates of changes (forcings and temperatures) could be
compatible with the base period used in Figure 1).

We will cross reference this section from ours.
Tim and Keith

Dr Timothy J Osborn
Climatic Research Unit
School of Environmental Sciences, University of East Anglia
Norwich NR4 7TJ, UK
phone: +44 1603 592089
fax: +44 1603 507784


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

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