Image: STANFORD UNIVERSITY
Given the heated debate surrounding global warming, you probably won't find many people willing to wager money on its specific effects. That is, unless you live in Nenana, Alaska. For the past 84 years, participants in the Nenana Ice Classic have placed bets on when, exactly, the ice in the nearby Tenana River will melt. A study published today in Science by two Stanford University researchers exploits this unconventional data set to investigate the effects of our changing climate.
Because of the high stakes involved in guessing the correct time for the breakup of the ice (this year's jackpot was $308,000), the scientists assert that the contest's records are quite accurate. Additionally, the location of the tripod on the frozen river (see image) has not changed significantly over the course of the competition, thereby providing consistent statistics. The tripod moves when the melting river ice breaks up, triggering a clock once it moves 100 feet. "Because scientists weren't think about climate change 80 or 90 years ago, it's really important that people kept these data," co-author Raphael Sagarin says.
The scientists determined that the ice breakup now occurs five and a half days earlier than it did in 1917. "Warmer climate would be expected to advance the time of breakup through both thermal (direct melting) and dynamic effects (mechanical forces from upstream drift ice)," they write, "due to thinning ice and increased snowmelt runoff into rivers." The researchers further note that the records from the contest also match well with other climate data available for the area. "These results show that springtime is coming earlier," Sagarin says.
In a related report in the same issue, Josep Pe¿uelas and Iolanda Filella of the Center for Ecological Research and Forestry Applications in Barcelona cite growing evidence that climate change is affecting the annual cycles of plants and animals. The leaves of deciduous plants in both Europe and North America, they report, unfurl some six to 26 days earlier than they did several decades ago, and plant flowering is similarly affected. "All these plant phenological changes are highly correlated with temperature changes," the authors write. The warmer climate also affects animals, they assert, noting that changes in insect flight behavior, frog calling and bird egg-laying and migration have all been detected