date: Sat, 12 Jun 2004 13:31:36 -0400 from: Henry Pollack subject: Borehole climate reconstructions to: ralley@essc.psu.edu, ammann@ucar.edu, david.m.anderson@noaa.gov, k.briffa@uea.ac.uk, broecker@ldeo.columbia.edu, drdendro@ldeo.columbia.edu, tcrowley@duke.edu, mark.eakin@noaa.gov, esper@wsl.ch, fidel@gkss.de, jhansen@giss.nasa.gov, hegerl@duke.edu, p.jones@uea.ac.uk, cfk@lanl.gov, kondratyev@KK10221.spb.edu, mmaccrac@comcast.net, anders@misu.su.se, t.osborn@uea.ac.uk, jto@u.arizona.edu, simon.tett@metoffice.com, trenbert@ucar.edu, storch@gkss.de, weaver@ocean.seos.uvic.ca, wigley@ucar.edu, connie.woodhouse@noaa.gov, zorita@gkss.de Dear Colleagues, Attached are two papers, recently published in the Journal of Geophysical Research - Atmospheres, to which I call your attention: Pollack, H.N. and Smerdon, J.E., Borehole climate reconstructions: Spatial structure and hemispheric averages, J. Geophys. Res. 109, D11106, doi:10.1029/2003JD004163, 2004 Rutherford, S. and Mann, M.E., Correction to "Optimal surface temperature reconstructions using terrestrial borehole data", J. Geophys. Res. 109, D11107,doi:10.1029/2003JD004290, 2004 The first paper presents a detailed study of the aggregation of individual borehole reconstructions to form a hemispheric average; the investigation also demonstrates that when the borehole reconstructions are properly aggregated, they display significant spatial correlation with the surface air temperature (SAT) at sub-hemispheric spatial scales. In this paper we also identify an error in the paper "Optimal surface temperature reconstructions using terrestrial borehole data" by Mann et al. [JGR 108(D7),4203, doi:10.1029/2002JD002532], and discuss the ramifications. Rutherford and Mann acknowledge the error in the second paper attached. I call these papers to your attention to help quell the propagation of the identified error, and to reiterate that in terms of an average northern hemisphere history over the past five centuries, the borehole reconstructions yield a warming of the ground surface of about 1K, half of which occurred in the 20th century. Cheers, Henry ___ ___ Henry N. Pollack [ \ / ] Professor of Geophysics | \/ | Department of Geological Sciences |MICHIGAN| University of Michigan [___]\/[___] Ann Arbor, Michigan 48109-1063, U.S.A. Phone: 734-763-0084 FAX: 734-763-4690 e-mail: hpollack@umich.edu URL: http://www.geo.lsa.umich.edu/~hpollack URL: www-personal.umich.edu/~hpollack/book.html Attachment Converted: "c:\eudora\attach\Rutherford and Mann_Journal.pdf" Attachment Converted: "c:\eudora\attach\Pollack and Smerdon_Journal.pdf"