When You Get Your Picture on the Cover of - The Hockey Stick and the Climate Wars - page 95

applied retention criteria that we had obtained using our convention (modern centering) to PCs
calculated from the tree ring data based on a different convention (long-term centering). Through this
error, they eliminated the key hockey stick pattern of long-term variation. 20 In effect, McIntyre and
McKitrick had “buried” or “hidden” the hockey stick. They had chosen to throw out a critical pattern
in the data as if it were noise, when an objective analysis unambiguously identified it as a significant
pattern. 21 It was essentially the same error they had committed in their 2003 paper, wherein the key
proxy data were simply thrown out 22 —it's just that here, they were thrown out in a way that was not
as obvious.
The Rebuttals
While we had refuted a number of the McIntyre and McKitrick claims ourselves in the peer reviewed
literature, 23 analyses by a number of other groups over time would independently confirm that the
various claims McIntyre and McKitrick had made were false or misleading. The first such analysis
was conducted by National Center for Atmospheric Research (NCAR) scientists Eugene Wahl and
Caspar Ammann who, in May 2005, announced findings that “dispute McIntyre and McKitrick's
alleged identification of a fundamental flaw that would significantly bias the MBH climate
reconstruction toward a hockey stick shape.” They concluded that “the highly publicized criticisms of
the MBH graph are unfounded.” 24
Wahl and Ammann demonstrated that the hockey stick was not an artifact of PCA conventions
and that the basic result is robust as long as key proxy records are not thrown out (either explicitly, as
in the original 2003 McIntyre and McKitrick paper, or implicitly through the use of erroneous
selection rules, as in their 2005 paper). Wahl and Ammann closely reproduced the original hockey
stick reconstruction with the data available in the public domain, even after accepting—for the sake
of argument—all potentially valid points made by McIntyre and McKitrick (e.g., adopting their long-
term centering convention, but using correct PC selection rules). They showed that, had McIntyre and
McKitrick subjected their alternative reconstruction to the statistical validation tests stressed in
MBH98 and MBH99 (and nearly all related studies), it would have failed these critical tests.
McIntyre and McKitrick, in short, had not only failed to reproduce the hockey stick by eliminating key
data, but their own results, unlike the MBH98 reconstruction, failed standard statistical tests of
validity. (Wahl and Ammann provided all data and code used online so interested individuals could
check any of these findings for themselves.)