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In the hockey stick controversy, the data and methods used in reconstructions of the temperature record of the past 1000 years have been disputed. Reconstructions have consistently shown that the rise in the instrumental temperature record of the past 150 years is not matched in earlier centuries, and the name "hockey stick graph" was coined for figures showing a long-term decline followed by an abrupt rise in temperatures. These graphs were publicised to explain the scientific findings of climatology, and in addition to scientific debate over the reconstructions, they have been the topic of political dispute. The issue is part of the global warming controversy and has been one focus of political responses to reports by the Intergovernmental Panel on Climate Change (IPCC). Arguments over the reconstructions have been taken up by fossil fuel industry funded lobbying groups attempting to cast doubt on climate science.〔, 〕 The use of proxy indicators to get quantitative estimates of the temperature record of past centuries was developed from the 1990s onwards, and found indications that recent warming was exceptional. The reconstruction introduced the "Composite Plus Scaling" (CPS) method used by most later large-scale reconstructions,〔.〕 and its findings were disputed by Pat Michaels at the United States House Committee on Science. In 1998 Michael E. Mann, Raymond S. Bradley and Malcolm K. Hughes developed new statistical techniques to produce (MBH98), the first eigenvector-based climate field reconstruction (CFR). This showed global patterns of annual surface temperature, and included a graph of average hemispheric temperatures back to 1400. In (MBH99) the methodology was extended back to 1000.〔〔 The term ''hockey stick'' was coined by the climatologist Jerry Mahlman, to describe the pattern this showed, envisaging a graph that is relatively flat to 1900 as forming an ice hockey stick's "shaft", followed by a sharp increase corresponding to the "blade".〔〔.〕 A version of this graph was featured prominently in the 2001 IPCC Third Assessment Report (TAR), along with four other reconstructions supporting the same conclusion.〔 The graph was publicised, and became a focus of dispute for those opposed to the strengthening scientific consensus that late 20th century warmth was exceptional.〔 ("Part three: Hockey stick graph took pride of place in IPCC report, despite doubts" ).〕 Those disputing the graph included Pat Michaels, the George C. Marshall Institute and Fred Singer. A paper by Willie Soon and Sallie Baliunas claiming greater medieval warmth was used by the Bush administration chief of staff Philip Cooney to justify altering the first Environmental Protection Agency ''Report on the Environment''. The paper was quickly dismissed by scientists in the Soon and Baliunas controversy, but on July 28, Republican Jim Inhofe spoke in the Senate citing it to claim "that man-made global warming is the greatest hoax ever perpetrated on the American people".〔 Later in 2003, a paper by Stephen McIntyre and Ross McKitrick disputing the data used in MBH98 paper was publicised by the George C. Marshall Institute and the Competitive Enterprise Institute. In 2004 Hans von Storch published criticism of the statistical techniques as tending to underplay variations in earlier parts of the graph, though this was disputed and he later accepted that the effect was very small.〔(The Decay of the Hockey Stick ), Nature "Climate Feedback" blog post by von Storch. "... we do not think that McIntyre has substantially contributed in the published peer-reviewed literature to the debate about the statistical merits of the MBH and related method." (comment by von Storch & Zorita, May 7, 2007 07:35 PM, in response to multiple comments on their failure to acknowledge McIntyre and McKitrick's contributions)〕 In 2005 McIntyre and McKitrick published criticisms of the principal components analysis methodology as used in MBH98 and MBH99. The analysis therein was subsequently disputed by published papers including and which pointed to errors in the McIntyre and McKitrick methodology. In June 2005 Rep. Joe Barton launched what Sherwood Boehlert, chairman of the House Science Committee, called a "misguided and illegitimate investigation" into the data, methods and personal information of Mann, Bradley and Hughes. At Boehlert's request 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.〔, ("Part four: Climate change debate overheated after sceptics grasped 'hockey stick'" ).〕 Barton and U.S. Rep. Ed Whitfield requested Edward Wegman to set up a team of statisticians to investigate, and they supported McIntyre and McKitrick's view that there were statistical failings, although they did not quantify whether there was any significant effect. They also produced an extensive network analysis which has been discredited by expert opinion and found to have issues of plagiarism. Arguments against the MBH studies were reintroduced as part of the Climatic Research Unit email controversy, but dismissed by eight independent investigations. More than two dozen reconstructions, using various statistical methods and combinations of proxy records, have supported the broad consensus shown in the original 1998 hockey-stick graph, with variations in how flat the pre-20th century "shaft" appears.〔〔.〕 The 2007 IPCC Fourth Assessment Report cited 14 reconstructions, 10 of which covered 1,000 years or longer, to support its strengthened conclusion that it was likely that Northern Hemisphere temperatures during the 20th century were the highest in at least the past 1,300 years.〔 Over a dozen subsequent reconstructions, including Mann et al. 2008 and , have supported these general conclusions. ==Background== Paleoclimatology dates back to the 19th century, and the concept of examining varves in lake beds and tree rings to track local climatic changes was suggested in the 1930s. In the 1960s, Hubert Lamb generalised from historical documents and temperature records of central England to propose a Medieval Warm Period from around 900 to 1300, followed by Little Ice Age. This was the basis of a "schematic diagram" featured in the IPCC First Assessment Report of 1990 beside cautions that the medieval warming might not have been global.〔.〕 Early quantitative reconstructions were published in the 1980s.〔. .〕 Publicity over the concerns of scientists about the implications of global warming led to increasing public and political interest, and the Reagan administration, concerned in part about the political impact of scientific findings, successfully lobbied for the 1988 formation of the Intergovernmental Panel on Climate Change to produce reports subject to detailed approval by government delegates.〔; 〕 The IPCC First Assessment Report in 1990 noted evidence that Holocene climatic optimum around 5,000-6,000 years ago had been warmer than the present (at least in summer) and that in some areas there had been exceptional warmth during "a shorter Medieval Warm Period (which may not have been global)" about AD 950-1250, followed by a cooler period of the Little Ice Age which ended only in the middle to late nineteenth century. The report discussed the difficulties with proxy data, "mainly pollen remains, lake varves and ocean sediments, insect and animal remains, glacier termini" but considered tree ring data was "not yet sufficiently easy to assess nor sufficiently integrated with indications from other data to be used in this report." A "schematic diagram" of global temperature variations over the last thousand years〔.〕 has been traced to a graph based loosely on Lamb's 1965 paper, nominally representing central England, modified by Lamb in 1982.〔 Mike Hulme describes this schematic diagram as "Lamb's sketch on the back of an envelope", a "rather dodgy bit of hand-waving".〔.〕 Archives of climate proxies were developed: in 1993 Raymond S. Bradley and Phil Jones composited historical records, tree-rings and ice cores for the Northern Hemisphere from 1400 up to the 1970s to produce a decadal reconstruction.〔.〕 Like later reconstructions including the MBH "hockey stick" studies, their reconstruction indicated a slow cooling trend followed by an exceptional temperature rise in the 20th century.〔.〕 This paper introduced the "Composite Plus Scaling" (CPS) method which was subsequently used by most large-scale climate reconstructions of hemispheric or global average temperatures.〔.〕 The IPCC Second Assessment Report (SAR) of 1996 featured Figure 3.20 showing this decadal summer temperature reconstruction together with a separate curve plotting instrumental thermometer data from the 1850s onwards. It stated that in this record, warming since the late 19th century was unprecedented. The section proposed that "The data from the last 1000 years are the most useful for determining the scales of natural climate variability". Recent studies including the 1994 reconstruction by Hughes and Diaz questioned how widespread the Medieval Warm Period had been at any one time, thus it was not possible "to conclude that global temperatures in the Medieval Warm Period were comparable to the warm decades of the late 20th century." The SAR concluded, "it appears that the 20th century has been at least as warm as any century since at least 1400 AD. In at least some areas, the recent period appears to be warmer than has been the case for a thousand or more years".〔, pp. 173–176, fig 3.20; .〕 Tim Barnett of the Scripps Institution of Oceanography was working towards the next IPCC assessment with Phil Jones, and in 1996 told journalist Fred Pearce "What we hope is that the current patterns of temperature change prove distinctive, quite different from the patterns of natural variability in the past".〔.〕 Tree ring specialist Keith Briffa's February 1998 study reporting a divergence problem affecting some tree ring proxies after 1960 warned that this problem had to be taken into account to avoid overestimating past temperatures.〔.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hockey stick controversy」の詳細全文を読む スポンサード リンク
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