North Report

The North Report was a 2006 report evaluating reconstructions of the temperature record of the past two millennia, providing an overview of the state of the science and the implications for understanding of global warming. It was produced by a National Research Council committee, chaired by Gerald North, at the request of Representative Sherwood Boehlert as chairman of the U.S. House of Representatives Committee on Science.These reconstructions had been dubbed ""hockey stick graphs"" after the 1999 reconstruction by Mann, Bradley and Hughes (MBH99), which used the methodology of their 1998 reconstruction covering 600 years (MBH98). A graph based on MBH99 was featured prominently in the 2001 IPCC Third Assessment Report (TAR), and became a focus of the global warming controversy over the 1997 Kyoto Protocol. It was disputed by various contrarians, and in the politicisation of this hockey stick controversy the New York Times of 14 February 2005 hailed a paper by businessman Stephen McIntyre and economist Ross McKitrick (MM05) as undermining the scientific consensus behind the Kyoto agreement. On 23 June 2005, Rep. Joe Barton, chairman of the House Committee on Energy and Commerce, with Ed Whitfield, Chairman of the Subcommittee on Oversight and Investigations, wrote joint letters referring to issues raised by the Wall Street Journal article, and demanding that Mann, Bradley and Hughes provide full records on their data and methods, finances and careers, information about grants provided to the institutions they had worked for, and the exact computer codes used to generate their results. Boehlert said this was a ""misguided and illegitimate investigation"" into something that should properly be under the jurisdiction of the Science Committee, and in November 2005 after Barton dismissed the offer of an independent investigation organised by the U.S. National Academy of Sciences, Boehlert requested the review, which became the North Report.The North Report went through a rigorous review process, and was published on 22 June 2006. It concluded ""with a high level of confidence that global mean surface temperature was higher during the last few decades of the 20th century than during any comparable period during the preceding four centuries"", justified by consistent evidence from a wide variety of geographically diverse proxies, but ""Less confidence can be placed in large-scale surface temperature reconstructions for the period from 900 to 1600"". It broadly agreed with the basic findings of the original MBH studies, which subsequently been supported by other reconstructions and proxy records, while emphasising uncertainties over earlier periods. The principal component analysis methodology that McIntyre and McKitrick had contested had a small tendency to bias results so was not recommended—but it had little influence on the final reconstructions, and other methods produced similar results.