Hip-checking Michael Mann 

An academic paper soon to be published in the Annals of Applied Statistics by Northwestern statistician Blakeley McShane and the University of Pennsylvania’s Abraham Wyner completely demolishes Penn State climatologist Michael Mann’s infamous hockey stick graph, cited by environmental activists as “scientific proof” of man-made global warming.

Statistician William Briggs has the best (and funniest) explanation of the pair’s devastating analysis (“A Statistical Analysis of Multiple Temperature Proxies: Are Reconstruction of Surface Temperatures Over the Last 1000 Years Reliable?”): “Statistically speaking, McShane and Wyner emulate [Gordie] Howe by applying a forearm check to the throat to Mann’s proxy reconstruction of temperature, cracking his hockey stick irreparably.” Briggs goes on to explain how the paper “hip checks” Mann and gives him a “high stick to the chops” before “leaving his models sprawling on the ice.”

McShane and Wyner not only destroy Mann’s argument, they unambiguously reject the statistical methods used by other paleoclimatologists to reconstruct past temperature data:

“We conclude unequivocally that the evidence for a ‘long-handled’ hockey stick (where the shaft of the hockey stick extends to the year 1000 AD) is lacking in the data. The fundamental problem is that there is a limited amount of proxy data which dates back to 1000 AD; what is available is weakly predictive of global annual temperature. Our backcasting methods, which track quite closely the methods applied most recently in Mann (2008) to the same data, are unable to catch the sharp run up in temperatures recorded in the 1990s, even in-sample…”

“In sum, these results suggest that the ninety-three sequences that comprise the 1,000 year old proxy record simply lack power to detect a sharp increase in temperature….Once one admits the possibility of regime changes in the instrumental period, it raises the question of whether such changes exist elsewhere over the past 1,000 years. Furthermore, it implies that up to half of the already short instrumental record is corrupted by anthropogenic factors, thus undermining paleoclimatology as a statistical enterprise.” (Emphasis added)

Briggs summarizes their findings: “It means we cannot tell—using these data and this model—with any reasonable certainty if temperatures have changed plus or minus 1 degree Centigrade over the last thousand years… Finally, we have our Amen, the touch of Grace, the last element of a Gordie Howe hat trick, and worthy of an octopus tossed onto the ice: ‘Climate scientists have greatly underestimated the uncertainty of proxy-based reconstructions and hence have been overconfident in their models.’”

Game’s over. Give Mann a polar ice pack and send him to the showers.

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Staff Report

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