Jun 22 2006
From The Space Library
An independent scientific panel, convened by the National Academy of Sciences’ (NAS’s) NRC, issued a report evaluating the results of a controversial 1999 study conducted by climatologist Michael E. Mann. Mann and his researchers had concluded that the warming of the Northern Hemisphere during the last decades of the twentieth century had no precedent within the past 1,000 years, and that the 1990s—particularly 1998—were the warmest years during that period. The study included a graph that had acquired the nickname “hockey stick,” becoming an environmentalist icon. The graph depicted little temperature variation in the Northern Hemisphere for almost 1,000 years, followed by a sharp upward hook representing recent rising temperatures. NAS had prepared the report, Surface Temperature Reconstructions for the Last 2,000 Years, at the request of House Science Committee Chairman Sherwood L. Boehlert (RNY). The panel had found “sufficient evidence from tree rings, retreating glaciers, and other ‘proxies’ of past surface temperatures to say with a high level of confidence that the last few decades of the twentieth century were warmer than any comparable period in the last 400 years.” Although this conclusion vindicated the main argument of Mann’s study for the most part, the panel cautioned that scientists had found less empirical evidence proving that Northern Hemisphere warming had no precedent before 1600. The panel also stated that “because of larger uncertainties in temperature reconstructions for decades and individual years, and because not all proxies record temperatures for such short timescales,” they had less confidence in the team’s conclusions about the 1990s.
Juliet Eilperin, “Study Confirms Past Few Decades Warmest on Record,” Washington Post, 23 June 2006; National Academies Office of News and Public Information, “ ‘High Confidence’ That Planet Is Warmest in 400 Years; Less Confidence in Temperature Reconstructions Prior to 1600,” press release, 22 June 2006, http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=11676 (accessed 9 August 2010); Andrew C. Revkin, “Panel Supports a Controversial Report on Global Warming,” New York Times, 23 June 2006; see also National Research Council Committee, Surface Temperature Reconstructions for the Last 2,000 Years (Washington, DC: National Academies Press, 2006), http://www.nap.edu/catalog/11676.html (accessed 1 October 2010).
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