A key piece of evidence linking human activity to climate change turns out to be an artifact of poor mathematics. At issue is the famous "hockey stick" graph, which purports to show that we are now experiencing the warmest climate in a millennium, and that the earth, after remaining cool for centuries during the medieval era, suddenly began to heat up about 100 years ago--just at the time that the burning of coal and oil led to an increase in atmospheric levels of carbon dioxide. But now two Canadian scientists have uncovered a fundamental flaw in the computer program that was used to produce the hockey stick.
http://www.technologyreview.com/articles/04/10/wo_muller101504.asp?trk=nl