|Contacts for This Release
The Hockey Stick Controversy
New Analysis Reproduces Graph of Late 20th Century
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
The National Center for Atmospheric Research and UCAR Office of Programs are operated by UCAR under the sponsorship of the National Science Foundation and other agencies. Opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any of UCAR's sponsors.