Hockey stick controversy
The hockey stick controversy refers to debates over the technical correctness and implications for
global warming of graphs showing reconstructed estimates of thetemperature record of the past 1000 years;
at a political level, the debate is about the use of these graphs to convey complex science to the public, and
the question of the
global warming of graphs showing reconstructed estimates of thetemperature record of the past 1000 years;
at a political level, the debate is about the use of these graphs to convey complex science to the public, and
the question of the
robustness of the assessment presented by the Intergovernmental Panel on Climate Change (IPCC).
By the late 1990s a number of competing teams were using proxy indicators to estimate the temperature record
of past centuries, and finding suggestions that recent warming was exceptional.[1] In 1998
Michael E. Mann, Raymond S. Bradley and Malcolm K. Hughes produced the first quantitative
hemispheric-scale reconstruction, from an analysis of a variety of measures, which they summarised
in a graph going back to 1400 showing recent measured temperatures increasing sharply.
Their 1999 paper extended this study back to 1000, and included a graph which was featured prominently in the
2001 United Nations Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report(TAR) as
supporting the mainstream view of climate scientists that there had been a relatively sharp rise in temperatures
during the second half of the 20th century. It became a focus of dispute for those opposed to this
strengthening scientific consensus.[2] The term hockey stick was coined by the climatologist Jerry Mahlman, to
describe the pattern, envisaging a graph that is relatively flat to 1900 as forming the hockey stick's "shaft", followed
by a sharp increase corresponding to the "blade".[3]
of past centuries, and finding suggestions that recent warming was exceptional.[1] In 1998
Michael E. Mann, Raymond S. Bradley and Malcolm K. Hughes produced the first quantitative
hemispheric-scale reconstruction, from an analysis of a variety of measures, which they summarised
in a graph going back to 1400 showing recent measured temperatures increasing sharply.
Their 1999 paper extended this study back to 1000, and included a graph which was featured prominently in the
2001 United Nations Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report(TAR) as
supporting the mainstream view of climate scientists that there had been a relatively sharp rise in temperatures
during the second half of the 20th century. It became a focus of dispute for those opposed to this
strengthening scientific consensus.[2] The term hockey stick was coined by the climatologist Jerry Mahlman, to
describe the pattern, envisaging a graph that is relatively flat to 1900 as forming the hockey stick's "shaft", followed
by a sharp increase corresponding to the "blade".[3]
In 2003, Willie Soon and Sallie Baliunas argued against this pattern in a paper which was quickly dismissed as faulty
in the Soon and Baliunas controversy.[1] In the United States there was already a hot political dispute over action on
global warming following lobbying regarding the 1997 Kyoto Protocol, and on July 28, Republican Jim Inhofe made
a Senate speech citing Soon and Baliunas to support his view "that man-made global warming is the greatest hoax
ever perpetrated on the American people".[4] Also in 2003,Stephen McIntyre and Ross McKitrick published a paper
questioning the statistical methods used in the Mann et al. paper, and there was continued debate on these issues
.Hans von Storch regards that paper as of little consequence, and believes his paper of 2004 to be the first significant
criticism.[5] At the request of Congress, a panel of scientists convened by the National Research Council was set up
, which reported in 2006 supporting Mann's findings with some qualifications, including agreeing that there were some
statistical failings but these had little effect on the result.[6] U.S. Rep. Joe Barton and U.S. Rep. Ed Whitfield
requested Edward Wegman to set up a team of statisticians to investigate, and they supported the view that
there were statistical failings, although their report has itself been criticized on several grounds.
in the Soon and Baliunas controversy.[1] In the United States there was already a hot political dispute over action on
global warming following lobbying regarding the 1997 Kyoto Protocol, and on July 28, Republican Jim Inhofe made
a Senate speech citing Soon and Baliunas to support his view "that man-made global warming is the greatest hoax
ever perpetrated on the American people".[4] Also in 2003,Stephen McIntyre and Ross McKitrick published a paper
questioning the statistical methods used in the Mann et al. paper, and there was continued debate on these issues
.Hans von Storch regards that paper as of little consequence, and believes his paper of 2004 to be the first significant
criticism.[5] At the request of Congress, a panel of scientists convened by the National Research Council was set up
, which reported in 2006 supporting Mann's findings with some qualifications, including agreeing that there were some
statistical failings but these had little effect on the result.[6] U.S. Rep. Joe Barton and U.S. Rep. Ed Whitfield
requested Edward Wegman to set up a team of statisticians to investigate, and they supported the view that
there were statistical failings, although their report has itself been criticized on several grounds.
More than twelve subsequent scientific papers, using various statistical methods and combinations of proxy records
, produced reconstructions broadly similar to the original MBH hockey-stick graph, with variations in how flat the
pre-20th century "shaft" appears. Almost all of them supported the IPCC conclusion that the warmest decade in
1000 years was probably that at the end of the 20th century
, produced reconstructions broadly similar to the original MBH hockey-stick graph, with variations in how flat the
pre-20th century "shaft" appears. Almost all of them supported the IPCC conclusion that the warmest decade in
1000 years was probably that at the end of the 20th century
