It’s difficult to imagine how a guy who spends most of his time looking at endless columns of temperature records became a ‘fucking terrorist,’ ‘killer,’ or ‘one-world-government socialist.’ It’s even harder when you meet Michael Mann, a balding 45-year-old climate scientist who speaks haltingly and has a habit of nervously clearing his throat. And when you realize that the reason for all the hostility is a 12-year-old chart, it seems more than a little surreal.

Back in 1999, Mann-then a newly minted Ph.D. (PDF)-and a pair of colleagues constructed a chart that plotted historical climate data, spanning from 1000 to 1980. Because recorded temperatures only begin in the late 19th century, Mann and his team largely relied on so-called proxy records-measurements of tree rings, coral, and ice cores whose variations illustrate temperature changes over the years. The graph showed that after nearly 900 years of relatively stable temperatures, there was a sharp uptick starting in the 20th century.

You may have seen a version of the graph, known as the ‘hockey stick,’ in the film An Inconvenient Truth-the rise in carbon dioxide levels* is so steep, Al Gore uses a mechanical ladder to reach the most recent readings. The graph was featured […]