Media Advisory: The Hockey Stick Controversy
New Analysis Reproduces Graph of Late 20th Century Temperature Rise

May 11, 2005

BOULDER—Caspar Ammann, a paleoclimatologist at the National Center for Atmospheric Research (NCAR), is available to comment on the so-called hockey stick controversy discussed by Stephen McIntyre and Ross McKitrick today at the National Press Club in Washington, D.C. The hockey stick refers to the shape of a frequently cited graph of global mean temperature that shows a rapid rise between 1900 and 2000 after 900 years of relative stability.  The graph first appeared in a research paper by Michael Mann, Raymond Bradley, and Malcolm Hughes published in the journal Nature in 1998.

Ammann and Eugene Wahl of Alfred University have analyzed the Mann-Bradley-Hughes (MBH) climate field reconstruction and reproduced the MBH results using their own computer code. They found the MBH method is robust even when numerous modifications are employed.  Their results appear in two new research papers submitted for review to the journals Geophysical Research Letters and Climatic Change. The authors invite researchers and others to use the code for their own evaluation of the method.

Ammann and Wahl’s findings contradict an assertion by McIntyre and McKitrick that 15th century global temperatures rival those of the late 20th century and therefore make the hockey stick-shaped graph inaccurate.  They also dispute McIntyre and McKitrick’s alleged identification of a fundamental flaw that would significantly bias the MBH climate reconstruction toward a hockey stick shape. Ammann and Wahl conclude that the highly publicized criticisms of the MBH graph are unfounded.  They first presented their detailed analyses at the American Geophysical Union’s Fall Meeting in San Francisco last December and at the American Association of Geographers Annual Meeting in Denver this year.

McIntyre and McKitrick’s papers were published in Energy and Environment (2003 and 2005) and in Geophysical Research Letters (2005).

Ammann and Wahl superimpose their analysis, the MBH analysis, and the instrumental record.

 Related sites on the World Wide Web 

Re-evaluation of the Mann-Bradley-Huges climate reconstruction

Climate Web site explaining the hockey stick issues

Round table at the National Press Club today

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