Friday, April 13, 2012


cc: Eystein Jansen <>,,,
date: Thu, 13 Jan 2005 16:19:31 +0000
from: Tim Osborn <>
subject: Re: Need your help on something important
to: Jonathan Overpeck <>,Keith Briffa <>

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


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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

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