Hockey sticks, principal components, and spurious significance
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چکیده
[1] The ‘‘hockey stick’’ shaped temperature reconstruction of Mann et al. (1998, 1999) has been widely applied. However it has not been previously noted in print that, prior to their principal components (PCs) analysis on tree ring networks, they carried out an unusual data transformation which strongly affects the resulting PCs. Their method, when tested on persistent red noise, nearly always produces a hockey stick shaped first principal component (PC1) and overstates the first eigenvalue. In the controversial 15th century period, the MBH98 method effectively selects only one species (bristlecone pine) into the critical North American PC1, making it implausible to describe it as the ‘‘dominant pattern of variance’’. Through Monte Carlo analysis, we show that MBH98 benchmarks for significance of the Reduction of Error (RE) statistic are substantially under-stated and, using a range of cross-validation statistics, we show that the MBH98 15th century reconstruction lacks statistical significance. Citation: McIntyre, S., and R. McKitrick (2005), Hockey sticks, principal components, and spurious significance, Geophys. Res. Lett., 32, L03710, doi:10.1029/2004GL021750.
منابع مشابه
Reply to Ammann and Wahl: “comment on “hockey Sticks, Principal Components and Spurious Significance”
متن کامل
Reply to comment by von Storch and Zorita on ‘‘Hockey sticks, principal components, and spurious significance’’
[1] Von Storch and Zorita [2005] (hereinafter referred to as VZ) concur that the Mann et al. [1998] (hereinafter referred to as MBH98) principal component (PC) method ‘‘very often shows a hockey stick shaped pattern even if the data was by construction free of such structures’’ the Artificial Hockey Stick (AHS) effect. We did not claim that the AHS effect applied to all situations. We did claim...
متن کاملComment on ‘‘Hockey sticks, principal components, and spurious significance’’ by S. McIntyre and R. McKitrick
[1] McIntyre and McKitrick [2005] (hereinafter referred to as MM05) point out a bias in the Mann et al. [1998] (hereinafter referred to as MBH98) Northern Hemisphere temperature reconstruction, one tending to enhance trends during the last century. Having reproduced the statistical results of MM05, this comment is prompted by further questions regarding appropriate implementation of principal c...
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The following describes experimental methods for characterizing ice hockey pucks and sticks at game-like speeds. Pucks were characterized according to their coefficient of restitution (COR) and dynamic stiffness (DS) for different brands, speeds, and temperatures. The COR provided a measure of the puck’s elasticity, while the DS provided a measure of puck hardness. At room temperature, puck COR...
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تاریخ انتشار 2005