date: Tue, 9 Aug 2005 17:48:39 UT from: grlonline@agu.org subject: 2005GL024155 Request to Review from Geophysical Research Letters to: K.Briffa@uea.ac.uk Dear Dr. Briffa: Would you be willing and available to review "Are empirical climate reconstruction methods robust?" by Gerd Bürger, Ulrich Cubasch, submitted for possible publication in the Geophysical Research Letters. The manuscript's abstract is: 64 climate reconstructions, based on regression of temperature fields on multi-proxies and mutually distinguished by at least one of six standard criteria, cover an entire spread of millennial histories. No single criterion is accountable for the spread, which appears to depend on a complicated interplay of the criteria. The uncertainty is traced back to the fact that regression is applied here in an extrapolative manner, with millennial variations exceeding the standard calibration scale by a factor of 5 and more. Even if linearity still holds for that larger domain, the model error propagates in a way that is proportional to both the estimation error and the proxy variations, and is thus extrapolated accordingly. This is particularly critical for the parameter-loaded models of the analyzed kind. Without a model error estimate and without techniques to hold it small, it is not clear how these methods can be salvaged to become robust. If you agree to review this manuscript, I would ask for your comments within 14 days from your acceptance. To ACCEPT, click on the link below: If you are unable to review this manuscript at this time, I would appreciate any suggestions of other potential reviewers who would be qualified to examine this manuscript. (Via reply e-mail.) To DECLINE, click on the link below: If you have any questions or need more information feel free to reply to this e-mail. Thank you for your consideration and support of Geophysical Research Letters. Sincerely, Naohiro Yoshida Associate Editor Geophysical Research Letters