The IPCC, the “Hockey Stick” Curve, and the Illusion of Experience

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Date(s) - 11/18/200312:00 pm - 1:30 pm


The Intergovernmental Panel on Climate Change’s (IPCC) Third Assessment Report concluded that “it is likely that the rate and duration of the warming of the 20th century is larger than any other time during the last 1,000 years. The 1990s are likely to have been the warmest decade of the millennium in the Northern Hemisphere, and 1998 is likely to have been the warmest year.”

The primary basis for this assertion was a climate reconstruction that produced the so-called “hockey stick” shaped graph, which shows that the 20th century was unusually warm compared to preceding centuries. A new evaluation of the underlying data used to create that graph by Canadian businessman Stephen McIntyre and economist Ross McKitrick raises serious questions as to its validity.

McIntyre and McKitrick examined the construction and use of the data set of proxies for past climate, which were used to estimate the temperature record from 1400 to 1980. Their review found four categories of error: collation errors, unjustified truncation and extrapolation, use of obsolete data, and calculation mistakes. Correcting for these errors, they found that temperature for the early 15th century was actually higher than the 20th century.

The McIntyre-McKitrick findings challenge one of the most influential aspects of the climate change debate. The “hockey stick” graph has been accepted as fact by the international community and many domestic interests pushing the Kyoto Protocol and McCain-Lieberman.

Download PDF The IPCC the Hockey Stick Curve and the Illusion of Experience


[See the original paper by Stephen McIntyre and Ross McKitrick, “Corrections to the Mann et al (1998) Proxy Data Base and Northern Hemisphere Average Temperature Series” Energy and Environment 14(6) 751-772.]

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