From: Michael E. Mann To: mhughes@ltrr.arizona.edu Cc: raymond s. bradley; srutherford@rwu.edu Subject: Re: Yang et al 2002 Date: Thursday, March 17, 2005 5:54:18 AM Malcolm, Apparently you missed the followup message. I'm forwarding that. Ray seemed to be satisfied w/ my suggestion... Message to follow shortly, mike At 11:28 PM 3/16/2005, mhughes@ltrr.arizona.edu wrote: Hi guys - I vote against including anything just because it has a significant correlation with some climate variable in the 20th century. This is a necessary but far from sufficient condition. Someone who knows a particular kind of proxy can often give very good reasons, related to consistent criteria, for excluding such a record - for example, if the quality of the chronology is unknown or not good enough (e.g. just based on a couple of radiocarbon dates). Or, if no consistent case has been made by the original authors of the record for a climate signal, beyond mere correlation. My understanding was that it was precisely to check such matters that Ray and I have been working through all this stuff. If we're going to include "mystery proxies" solely on the basis of a correlation, he and I and the people working with us have been wasting our time. In the case of the Yang et al, we already have good records from the Tibetan plateau from Shao Xuemei (not used by Yang) and Achim Brauening. He (Achim) is one of the authors of the Yang et al paper, and, when asked, volunteered the eastern Tibet record we have included. I hope tomorrow to check up on the JApanese tree-ring del C13 record. If it's the one I think, it's worthless as it's based on only a single tree with no good case for a climate signal and no cross-dating. Cheers, Malcolm Quoting "Michael E. Mann" : > > > HI Ray, > > > Well, one thing that is different here is that we are actually screening > all proxies to see if they have a verifiable signal (temperature or > precip) against the instrumental record. So we're trying to use an > objective measure, rather than just deciding what we think is good or > not. > > > I agree we have to eliminate redundant proxies, but for the non-redundant > proxies, I vote for letting the screening process decide if we use them > or not. > > > Now, w/ other issues, I agree w/ Malcolm that we have to apply other > considerations. For example. the screening process cannot protect us from > tree-ring series that degrade back in time because of decreasing # of > contributing chronologies, etc., so here we have to apply an explicit > quality control (e.g. minimum of 10 samples). If there is reason to > believe that some of the other proxies may degrade back in time, I agree > that they should be eliminated where we believe the degradation begins to > happen. > > > Do you think there are any issues of this sort w/ any of the other > proxies (including the ones used by Yang et al)? > > > Thanks, > > > Mike > > > At 11:56 AM 3/16/2005, raymond s. bradley wrote: > > Mike: > > You suggested that we include the Yang et al data set. I don't > think we should. It is made up of a rag-bag of records (a la > Crowley) that either already duplicate series that we have, or are > records that have an unclear relationship to temperature/climate. > > Specifically, their composite series is made up of: > > > ice core data from Guliya & Dunde--we > have > > Dulan > " > tree-ring indices" and "Tibet" tree ring record [" 12 temperature-sensitive > tree-ring series from various parts of Tibet"]-we may have some of these? > > winter temperature from Eastern China--we have > > d13C in wood cellulose in tree9s) from Japan-- I don't know if this means > anything > > d18O in peat cellulose from Jinchuan---- I don't know if this means anything > > total organic carbon content (TOC) and the C/N ratio records from Great Ghost > Lake and Jiaming Lake in Taiwan----I don't know if this means anything > > > So...I suggest that we do not include these composite series. > > I have now sent Scott the Black et al. G. Bulloides series > > ray > > > > > > > > > > > Raymond S. Bradley > > Director, Climate System Research Center* > > Department of Geosciences, University of Massachusetts > > Morrill Science Center > > 611 North Pleasant Street > > AMHERST, MA 01003-9297 > > > Tel: 413-545-2120 > > Fax: 413-545-1200 > > *Climate System Research Center: 413-545-0659 > > < http://www.paleoclimate.org> > > Paleoclimatology Book Web Site: http://www.geo.umass.edu/climate/paleo/html > > Publications (download .pdf files): > http://www.geo.umass.edu/faculty/bradley/bradleypub.html > > ______________________________________________________________ > > Professor Michael E. Mann > > Department of Environmental Sciences, Clark Hall > > University of Virginia > > Charlottesville, VA 22903 > > _______________________________________________________________________ > > e-mail: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137 > > http://www.evsc.virginia.edu/faculty/people/mann.shtml > > > ______________________________________________________________ Professor Michael E. Mann Department of Environmental Sciences, Clark Hall University of Virginia Charlottesville, VA 22903 _______________________________________________________________________ e-mail: mann@virginia.edu Phone: (434) 924-7770 FAX: (434) 982-2137 http://www.evsc.virginia.edu/faculty/people/mann.shtml