NCPA - National Center for Policy Analysis


August 7, 2006

The Earth's climate over the last 2,000 years has been characterized by periods of warmer -- as well as significantly cooler -- temperatures than the present.  The global warming "hockey stick" picture of dramatic temperature rise in the last 100 years following 1,900 years of relatively constant temperature, is flawed.  Public policy -- especially public policy with such wide-ranging consequences as this -- should be based on science, not spin, says H. Sterling Burnett, a senior fellow with the National Center for Policy Analysis.

Several independent studies have called into question the hockey stick's conclusions:

  • A number of climate experts noted that the Earth experienced both a widely recognized Medieval Warm Period from about A.D. 800 to 1400, as well as the Little Ice Age from 1600 to 1850; the hockey stick missed both of these significant climate trends.
  • Other researchers found methodological flaws with the hockey stick, arguing some data sources were misused, several calculations were done incorrectly and some of the data were simply obsolete.


Because the hockey stick image has been regularly used to promote and justify proposed climate legislation, Congress asked the National Academy of Sciences (NAS) to examine the hockey stick controversy.  Their report, released in early July, confirmed many of the criticisms of the hockey stick:

  • Whereas the authors of the research that produced the hockey stick concluded "the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium," the NAS found little confidence could be placed in those claims.
  • The NAS also found the original researchers used proxy data for past temperature reconstructions that were unreliable, the historic climate reconstruction failed important tests for verifiability and the methods used underestimated the uncertainty in the conclusions reached.

Source: H. Sterling Burnett, "When warming's 'hockey stick' breaks," Washington Times, August 4, 2006.


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