Friday, December 30, 2011

1253631628.txt

From: Michael Mann <mann@meteo.psu.edu>
To: Tom Wigley <wigley@ucar.edu>
Subject: Re: help
Date: Tue, 22 Sep 2009 11:00:28 -0400
Cc: Phil Jones <p.jones@uea.ac.uk>, Caspar Ammann <ammann@ucar.edu>

Hey Tom, thanks for checking w/ me on this. Re, Moberg: Yes, in fact we (me, Phil, Tim,
Keith, Caspar, etc.) submitted a comment to Nature about the problem w/ the variance
scaling used by Moberg. It can easily be shown to inflate the low- frequency variance in
synthetic experiments. I've attached both the original comment (which they judged to be too
technical to merit publication) and also a J. Climate paper where we discussed the same
result (see Figure 5 and associated discussion). Re, Von Storch et al. Yes, the paper you
have in mind is Osborn et al Climate Dynamics '06. I only seem to have the preprint though
(attached), please let me know if I can be of any further help w/ an of this, mike p.s. you
can delete the U.Va email address--haven't been there for 4 years! On Sep 22, 2009, at
10:31 AM, Tom Wigley wrote: > Dear all, > > (Apologies Mike for email address confusion --
one of them will > get you I hope.) > > I need some help to finish a report I've had to
write for EPRI -- > which is due in a few days. Hence the questions below ... > > (1) The
Moberg paper (2005 Nature) is used by the skeptics as evidence > that most of recent
warming could still be natural. Has anyone > published a critique/criticism of this? It
seems to me take this > work is fundamentally flawed. First, variance scaling is crap >
statistics as it produces results with far less explained variance > than normal
least-squares regression. Second, the paper seems to > have no independent validation.
Third, what happens if one just takes > his low-frequency (numbered in his Fig. 1) points
and calculates > the area average? Surely this will have much greater variability > than
the full global mean? (If no-one has done this please let me > know -- I can do it very
easily myself.) But perhaps his scaling > method circumvents this "problem"? > > (2) What
is the paper of Caspar's (with Doug Nychka) that shows > that McIntyre is wrong? Are there
other papers I should see/cite > in this regard? > > (3) What are the papers that explain
what is wrong with the von > Storch ECHO simulation? I think Tim Osborn did something on
this. > > Many thanks for your help, > Tom. > -- 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: mann@psu.edu
University Park, PA 16802-5013 website: http://www.meteo.psu.edu/~mann/Mann/index.html
"Dire Predictions" book site:
http://www.essc.psu.edu/essc_web/news/DirePredictions/index.html Hey Tom,

thanks for checking w/ me on this.

Re, Moberg: Yes, in fact we (me, Phil, Tim, Keith, Caspar, etc.) submitted a comment to
Nature about the problem w/ the variance scaling used by Moberg. It can easily be shown to
inflate the low-frequency variance in synthetic experiments.

I've attached both the original comment (which they judged to be too technical to merit
publication) and also a J. Climate paper where we discussed the same result (see Figure 5
and associated discussion).

Re, Von Storch et al. Yes, the paper you have in mind is Osborn et al Climate Dynamics '06.
I only seem to have the preprint though (attached),

please let me know if I can be of any further help w/ an of this,

mike

p.s. you can delete the U.Va email address--haven't been there for 4 years!

On Sep 22, 2009, at 10:31 AM, Tom Wigley wrote:

Dear all,
(Apologies Mike for email address confusion -- one of them will
get you I hope.)
I need some help to finish a report I've had to write for EPRI --
which is due in a few days. Hence the questions below ...
(1) The Moberg paper (2005 Nature) is used by the skeptics as evidence
that most of recent warming could still be natural. Has anyone
published a critique/criticism of this? It seems to me take this
work is fundamentally flawed. First, variance scaling is crap
statistics as it produces results with far less explained variance
than normal least-squares regression. Second, the paper seems to
have no independent validation. Third, what happens if one just takes
his low-frequency (numbered in his Fig. 1) points and calculates
the area average? Surely this will have much greater variability
than the full global mean? (If no-one has done this please let me
know -- I can do it very easily myself.) But perhaps his scaling
method circumvents this "problem"?
(2) What is the paper of Caspar's (with Doug Nychka) that shows
that McIntyre is wrong? Are there other papers I should see/cite
in this regard?
(3) What are the papers that explain what is wrong with the von
Storch ECHO simulation? I think Tim Osborn did something on this.
Many thanks for your help,
Tom.

--
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: [1]mann@psu.edu
University Park, PA 16802-5013
website: [2]http://www.meteo.psu.edu/~mann/Mann/index.html
"Dire Predictions" book site:
[3]http://www.essc.psu.edu/essc_web/news/DirePredictions/index.html

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References

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