Saturday, December 03, 2011

Mann claim: "Phil and I weighted the records we used with respect to their decadal correlations with the instrumental gridpoint surface temperature data"; we "weighted them objectively"

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In our GRL article, Phil and I weighted the records we used with respect to their decadal correlations with the instrumental gridpoint surface temperature data for the same region (numbers in parentheses in attached figure 1 from the paper), so if a series is truly crap in an objectively determined sense, it got very low weight. The China series has a reasonable (r=0.22), but not great correlation--and it gets a moderate low weight. In my opinion, this is a better approach then simply deeming a record crap a priori (and then getting criticized for not considering it). We considered all available records with appropriate resolution that are putative temperature estimates, and weighted them objectively. We also did careful cross-validation on the resulting reconstruction using independent instrumental data, etc.---so I hardly think we are subject to criticism in how we used the available data, relative to other analyses that have been done... [Mann]

I loved this sentence: "Although a quantitative relationship between the proxy records of the Jinchuan peat, the Japan tree-ring series and the Taiwanese sediment records with modern climate data are not given in the original works, the qualitative connectivity with temperature as the dominant controlling factor has undoubtedly been verified" Oh, undoubtedly!! And these are 4 of the 9 series going into the "complete China" record.. Finally, they use another record based on "phenology" and (somehow) this provides a winter temperature series.... You just shouldn't grab anything that's in print and just use it 'cos it's there---that just perpetuates rubbish. [Bradley]

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