Clustering climate reconstructions

A systematic coherence analysis is presented for the set of the most prominent millennial reconstructions of Northern hemispheric temperature. The large number of mutual coherences underwent a clustering analysis that revealed five significant, mutually incoherent (“inconsistent”) clusters. The use of multiple proxies seems to be causing the 5 clustering, at least in part, but not in an easily definable, physical way. Alternatively, a multidimensional scaling is performed on the same set of coherences. This results in a graphic, two-dimensional rendering of the reconstructions whose geometry (location and distance) is given by the coherences. Both approaches offer complementary ways in dealing with the inconsistencies. 10