Support for Key Climate Change Graph

The "hockey stick" graph developed in the late 1990s by climate researchers continues to stir debate on global warming.

A National Academy of Sciences (NAS) panel announced on June 22 that there is sufficient evidence to say with a high level of confidence that the last few decades of the twentieth century were the warmest in the last 400 years. The panel also announced that there is far less evidence to accurately reconstruct surface temperatures dating from AD 900 to 1600. The NAS report was commissioned by Congress in response to a controversy over the now-famous “hockey stick” graph that illustrates a dramatic rise in recent temperatures that many say is evidence of global warming.

The debate over how accurately past temperatures can be reconstructed is somewhat redundant, some claim, given that the trio of scientists who developed the hockey stick graph in the late 1990s—Michael Mann, Raymond Bradley and Malcolm Hughes—addressed these uncertainties in the original paper (“Northern Hemisphere Temperature During the Past Millennium: Inferences, Uncertainties, and Limitations”). Two of the three authors of the contentious paper—Mann and Bradley—address the controversy at, a commentary website developed by climate scientists in 2004.

A version of the hockey stick diagram was presented in the Al Gore documentary An Inconvenient Truth, which is currently sweeping through American movie theaters. The film was just awarded a Humanitas Prize, which honors screenwriting that helps “liberate, enrich and unify society.” The last time a documentary won the award was in 1995 for Bill and Judith Davidson Moyers’ What Can We Do About Violence.

Source: New York Times,