Hockey sticks, principal components, and spurious significance

Hockey sticks, principal components, and spurious significance

[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 ...

Reply to comment by Huybers on ‘‘Hockey sticks, principal components, and spurious significance’’

[1] McIntyre and McKitrick [2005a] (hereinafter referred to as MM05) showed that the actual Mann et al. [1998] (hereinafter referred to as MBH98) PC method used an unreported short-centering method, which was biased towards producing a hockey stick shaped PC1 with an inflated eigenvalue. Huybers [2005] concurs with these particular findings, but argues that we ‘‘exaggerated’’ the MBH98 bias by ...

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...

Reply to Ammann and Wahl: “comment on “hockey Sticks, Principal Components and Spurious Significance”

Comment 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...