cc: Malcolm Hughes , Keith Briffa , Eugene R Wahl date: Sun, 30 Mar 2008 22:18:42 -0400 from: Caspar Ammann 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