Later in 2003 , a paper by Steve 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 . In 2005 , McIntyre and McKitrick published criticisms of the principal component 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 . 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
Climatic Research Unit email controversy
Climatic Research Unit email controversy
Hockey stick controversy