Monday, March 12, 2012

2448.txt

cc: Malcolm Hughes <mhughesatXYZxyzr.arizona.edu>, Keith Briffa <k.briffaatXYZxyz.ac.uk>, Eugene R Wahl <wahleatXYZxyzred.edu>
date: Sun, 30 Mar 2008 22:18:42 -0400
from: Caspar Ammann <ammannatXYZxyzr.edu>
subject: Re:
to: mannatXYZxyz.edu

Malcolm and Mike,

I wouldn't read too much into this. I believe that all we are looking at is the difference
between a statisticians approach and us in geophysics. The statisticians like to simulate
many ensembles. I had the same discussions with our guys at NCAR. The tendency for them is
to include all possible reconstructions and then describe the distributions. Our approach
has been to throw away reconstructions that don't make sense or that don't pass
verification. So its more philosophical than anything else.
Though Mike might be right in the sense that the choices can lead some of these approaches
astray. We had this with regard to the selections of uncertainty, what is actually
independent uncertainty. There a good and strong check on reality is necessary.
So we shall see in Vienna ...
Caspar

On Mar 30, 2008, at 8:32 PM, Michael Mann wrote:

Malcolm, in short, this looks like nonsense. there is nothing magic about 'Bayesian'
methods. Many of the methods we use can easily be recast as Bayesian approaches, the
critical question comes down to what the "prior" is. For example, in RegEM, the prior
is the first 'guess' in the iterative expectation-maximization algorithm. Of course, if
the final result is sensitive to that choice, one becomes a bit worried, the pitfall
indeed of many a Bayesian approach.
mike
Caspar Ammann wrote:

Malcolm,

are you referring to this?

[1]http://www.cosis.net/abstracts/EGU2007/03128/EGU2007-J-03128.pdf?PHPSESSID=e

Caspar

Caspar M. Ammann
National Center for Atmospheric Research
Climate and Global Dynamics Division - Paleoclimatology
1850 Table Mesa Drive
Boulder, CO 80307-3000
email: [2]ammannatXYZxyzr.edu tel: 303-497-1705 fax: 303-497-1348

--
Michael E. Mann
Associate 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: [3]mannatXYZxyz.edu
University Park, PA 16802-5013

[4]http://www.met.psu.edu/dept/faculty/mann.htm


Caspar M. Ammann
National Center for Atmospheric Research
Climate and Global Dynamics Division - Paleoclimatology
1850 Table Mesa Drive
Boulder, CO 80307-3000
email: [5]ammannatXYZxyzr.edu tel: 303-497-1705 fax: 303-497-1348

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