Several weeks ago, a new article (open access) on Sheep Mountain (Salzer et al 2014 , Env Res Lett) was published, based on updated (to 2009) sampling at Sheep Mountain.
One of the longstanding Climate Audit challenges to the paleoclimate community, dating back to the earliest CA posts, was to demonstrate out-of-sample validity of proxy reconstructions, by updating inputs subsequent to 1980. Because Graybill’s bristlecone chronologies were so heavily weighted in the Mann reconstruction, demonstrating out-of-sample validity at Sheep Mountain and other key Graybill sites is essential to validating the Mann reconstruction out of sample.
The new information shows dramatic failure of the Sheep Mountain chronology as an out-of-sample temperature proxy, as it has a dramatic divergence from NH temperature since 1980, the end of the Mann et al (and many other) reconstructions. While the issue is very severe for the Mann reconstructions, it affects numerous other reconstructions, including PAGES2K. Continue reading