Wednesday, May 9, 2012

4033.txt

cc: Phil Jones <p.jonesatXYZxyz.ac.uk>, Gavin Schmidt <gschmidtatXYZxyzs.nasa.gov>
date: Wed, 30 Sep 2009 12:41:44 -0400
from: Michael Mann <mannatXYZxyzeo.psu.edu>
subject: Re: attacks against Keith
to: Tim Osborn <t.osbornatXYZxyz.ac.uk>

Tim, Phil,

thanks for the clarification on this. the points are well taken. I'm fairly certain MBH98
and Mann et al PNAS are entirely independent of this particular (Briffa et al RCS version)
of the Urals/Yamal data, at least Malcolm believes that to be the case. It sounds as if
Mann and Jones is not. Meanwhile, Darrell Kaufman is re-rerunning their analysis w/out
Yamal to establish the result isn't sensitive to it (he's pretty confident its the case). I
don't know about the Hegerl/Crowley/Juckes et al analyses--do you know which of any used
this series, but interested if you have any insights into that yourself. we're trying to
get a tally on the number of studies that are completely independent of this particular
series, or have been shown to give largely similar conclusions w/out it (I think that is
true for Osborn and Briffa still, is it not?)

There are at least three issues we need to deal with here, 1) is the specific criticism of
Keith's particular rendition of the Yamal series legitimate (probably not--we hope this can
be established), 2) Which of the existing hemispheric reconstructions are specifically
affected (we know that many are not), 3) does this undermine the broader conclusions of
e.g. the IPCC on the key issue, i.e. anomalous nature of recent hemispheric warmth (no,
because many of the estimates are entirely independent of this series; the Mann et al PNAS
result was even shown to be independent of using tree-ring data at all).

thanks for your continued help w/ this,
miike
On Sep 30, 2009, at 12:15 PM, Tim Osborn wrote:

At 16:06 30/09/2009, Michael Mann wrote:

And Osborn and Briffa '06 is also immune to this issue, as it eliminated any combination
of up to 3 of the proxies and showed the result was essentially the same (fair to say
this Tim?).

Mike,
yes, you're right: figs S4-S6 in our supplementary information do indeed show results
leaving out individual, groups of two, and groups of three proxies, respectively. It's
attached.
I wouldn't say we were immune to the issue -- results are similar for these leave 1, 2 or 3
out cases, but they certainly are not as strong as the case with all 14 proxies. Certainly
in figure S6, there are some cases with 3 omitted (i.e. some sets of 11) where modern
results are comparable with intermittent periods between 800 and 1100.
Plus there is the additional uncertainty, discussed on the final page of the supplementary
information, associated with linking the proxy records to real temperatures (remember we
have no formal calibration, we're just counting proxies -- I'm still amazed that Science
agreed to publish something where the main analysis only involves counting from 1 to 14!
:-)).
But this is fine, since the IPCC AR4 and other assessments are not saying the evidence is
100% conclusive (or even 90% conclusive) but just "likely" that modern is warmer than MWP.
So, yes, it should be possible to find some subsets of data where MWP and Modern are
comparable and similarly for some seasons and regions. And as you've pointed out before,
if any season/region is comparable (or even has MWP>Modern) then it will probably be the
northern high latitudes in summer time (I think you published on this, suggesting that
combination of orbital forcing, land-use change and sulphate aerosols could cause this for
that season/region, is that right?).
So, this Yamal thing doesn't damage Osborn & Briffa (2006), but important to note that O&B
(2006) and others support the "likely" statement rather than being conclusive.
Cheers
Tim
<osbornsupp_revised06.doc>Dr Timothy J Osborn, Academic Fellow
Climatic Research Unit
School of Environmental Sciences
University of East Anglia
Norwich NR4 7TJ, UK
e-mail: [1]t.osborn@uea.ac.uk
phone: +44 1603 592089
fax: +44 1603 507784
web: [2]http://www.cru.uea.ac.uk/~timo/
sunclock: [3]http://www.cru.uea.ac.uk/~timo/sunclock.htm

--
Michael E. Mann
Professor
Director, Earth System Science Center (ESSC)
Department of Meteorology Phone: (814) 863-4075
503 Walker Building FAX: (814) 865-3663
The Pennsylvania State University email: [4]mann@psu.edu
University Park, PA 16802-5013
website: [5]http://www.meteo.psu.edu/~mann/Mann/index.html
"Dire Predictions" book site:
[6]http://www.essc.psu.edu/essc_web/news/DirePredictions/index.html

No comments:

Post a Comment