for National Geographic News
Global warming has loaded the dice in favor of heat waves and may be to blame for the scorching weather across much of the United States and Europe this summer, according to several of the world's leading climate scientists.
The U.S has already seen two severe heat waves this summer, and a third is currently frying the Midwest.
The U.K. just experienced what may be its hottest July on record. And August, often the warmest month of the year, is just beginning.
Scientists at the University of Oxford in England and the Hadley Centre for Climate Research and Prediction in Exeter, England, recently concluded that human-induced global warming has increased the odds by a factor of around six that Europe will see summer heat waves as extreme as that of 2003.
That heat wave killed an estimated 20,000 people.
And the odds are getting worse. By the middle of this century, every second European summer will be warmer than that of 2003, the scientists say. The study was published in the journal Nature in 2004.
"Some relatively rare events are being made a lot less rare by human influence on climate," said team leader Myles Allen, director of the Climate Dynamics Group at Oxford.
(Related news: "Rare Whales Appear off Scotland, Heat Wave Blamed" [July 28, 2006].)
A Safe Bet
"You can never say, but for global warming, this heat wave would never have happened," Allen said.
"What you can say is, global warming can increase the chance of a heat wave occurring, and a good analogy is loading the dice."
Loaded dice increase the odds of rolling a specific number. For example, by replacing the three on a die with a six, the odds of rolling a six are doubled. The odds of rolling two sixes in a row are quadrupled.
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