cc: Eugene R Wahl , Francis Zwiers date: Wed, 24 Oct 2007 09:31:41 -0600 from: Caspar Ammann subject: Wahl/Ammann vs Zwiers to: Phil Jones Hi Phil, a short note regarding what you perceive as differences in the reconstruction results by Lee et al (Zwiers) and ours. Actually, I don't think that there is anything that is inconsistent. There are a number of differences in the approach and so a one-to-one assessment is not possible. However, all general results agree very well with our observations and exercises, so I have absolutely no issues with Francis' results and paper (other than small bickering and suggestions for what is a really nice and clean paper): - more proxies: better performance (daahhh) - smoothing: better performance (! Key !) This is not systematically done in tradiational MBH, but I bet that this is actually the largest component for the improvement... you can do the acrobatics of xyz, in the end, if you do the fit on smoothed data, what is most representative of the CLIMATIC evolution in the series, then you get the best fits and amplitude preservation. - dependence on models: none - dependence on calibration period coverage: YES. Francis does not assess this, but we show that if you calibrate over period where a good chunk of the warmest and a good chunk of the coldest years are present, then your potential for amplitude loss is reduced - detrending: simply doesn't make sense, statistically as well as geophysically (removing the pattern that is associated with the global average and then try to recapture that in a truncated space??? stupid...) Caspar -- Caspar M. Ammann National Center for Atmospheric Research Climate and Global Dynamics Division - Paleoclimatology 1850 Table Mesa Drive Boulder, CO 80307-3000 email: [1]ammann@ucar.edu tel: 303-497-1705 fax: 303-497-1348