NCPA - National Center for Policy Analysis


July 14, 2006

Before 1999 the accepted view on climate change was that the world had undergone a warming period in the middle ages, followed by a mid-millennium cold spell and a subsequent warming period -- the current one. 

That all changed when paleoclimatologist Michael Mann's research paper eliminated the  Medieval warm period from the history books. With a nice, steady temperature oscillation that persists for centuries followed by a dramatic climb over the past century, Mann's work produced the "hockey stick" graph.

The trouble is that there's no reason to believe Mann, or his "hockey stick" graph of global temperature changes.  Subsequent studies have shown Mann's analysis to be less than definitive:

  • In 2003, Ross McKitrick and Steven McIntyre published an article in a peer-reviewed journal showing that Mann's methodology could produce hockey sticks from even random, trendless data.
  • Furthermore, in a soon to be released report by the House Energy and Commerce Committee, the three researchers -- Edward J. Wegman of George Mason University, David W. Scott of Rice University and Yasmin H. Said of Johns Hopkins University -- find that Mann's methodology is biased toward producing "hockey stick" shaped graphs.

In addition to debunking the hockey stick, Wegman goes a step further in his report, attempting to answer why Mann's mistakes were not exposed by his fellow climatologists.  His conclusion is that the coterie of most frequently published climatologists is so insular and close-knit that no effective independent review of the work of Mann is likely.

"There is a tightly knit group of individuals who passionately believe in their thesis. However, our perception is that this group has a self-reinforcing feedback mechanism and, moreover, the work has been sufficiently politicized that they can hardly reassess their public positions without losing credibility."

Source: Editorial, "Hockey Stick Hokum," Wall Street Journal, July 14, 2006


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