cc: Malcolm Hughes <mhughes@ltrr.arizona.edu>, Keith Briffa <k.briffa@uea.ac.uk>, Eugene R Wahl <wahle@alfred.edu>
date: Sun, 30 Mar 2008 22:18:42 -0400
from: Caspar Ammann <ammann@ucar.edu>
subject: Re:
to: mann@psu.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]ammann@ucar.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]mann@psu.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]ammann@ucar.edu    tel: 303-497-1705     fax: 303-497-1348

