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AN 84-year-old gambling event in Alaska is giving clues to the pace of global
warming. The Nenana Ice Classic is an annual contest that was started by bored
railroad workers. The organisers erect a wooden tripod on the frozen Tanana
river, and take bets on when it will fall through the melting ice in spring. “It
has become a huge contest,” says Raphael Sagarin at Stanford University. With
big prize money at stake—over $300,000 this year—the
competition has very precise records. Sagarin and Fiorenza Micheli found that in
recent years, the thaw has occurred on average 5.5…