Comment on “Hockey sticks, principal components, and spurious significance” by S. McIntyre and R. McKitrick


The “hockey stick” has been a contested icon in climate science since a historical reconstruction of northern hemisphere temperature during the last thousand years with a pattern of a hockey stick has been advanced by the IPCC as likely temperature history against which the recent warming trends should be evaluated (Houghton et al., 2001). This reconstruction has by now faced a number of severe challenges on different grounds. One of challenges was brought forward by McIntyre and McKitrik (2005), who had noted that the code, which generated the hockey stick contained, featured an uncommon mathematical detail (Section 1). In this study we examine if this uncommon detail, which under certain circumstances can result in artificial hockey sticks, would affect the final result of the reconstruction. We do this by redoing the analysis in the artificial world of a millennial GCM simulation (Section 2). It turns out, however the potentially misleading detail does not cause significant harm when reconstructing past climate.
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