Previously, Mann, Bradley and Hughes (1998) constructed a temperature history of the Northern Hemisphere for the period 1400-1980. The result was the well-known "hockey stick"-shaped graph suggesting that the 20th century was unusually warm when comparing it to preceding centuries. This graph has been widely cited by global warming alarmists and advocates of global warming legislation introduced by Sens. McCain and Lieberman (S. 139) now being debated in Congress.
"The particular 'hockey stick' shape derived in the Mann, et al. proxy construction -- a temperature index that decreases slightly between the early 15th century and early 20th century and then increases dramatically up to 1980 -- is primarily an artifact of poor data handling, obsolete data and incorrect calculation of principal components," stated the report.
The report detailed four categories of errors found in Mann, et al.
-- Collation errors
-- Unjustified truncation and extrapolation
-- Obsolete data
-- Calculation mistakes
The report by McIntyre and McKitrick was the first published audit that has been conducted of the data used in Mann, et al.
Please call 202-572-6231 to arrange an interview with Stephen McIntyre or Ross McKitrick. For an overview of the study and link to the journal Web site, go to http://www.uoguelph.ca/~rmckitri/research/trc.html.