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Extreme Hot Spells Are Being Driven by Climate Change, Study Says

Be it torrential rains or scorching heatwaves, weather extremes are increasingly being triggered by climate change, a new study suggests.

Swiss researchers have determined that a full 75 percent of the hot spells occurring over land can be traced to human activity, according to the study published Monday in Nature Climate Change.

Just 18 percent of heavy precipitation is related to climate change, reported researchers Erich Fischer and Reto Knutti, both from the Institute for Atmospheric and Climate Science at the Swiss Federal Institute of Technology in Zurich.

But that will jump to 40 percent if temperatures around the globe continue to rise, they predicted.

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Fischer and Knutti calculated the extent to which global warming could be changing the odds that heat waves and heavy rains could occur using daily outputs from 25 climate models. In their analysis they looked at simulations of weather from 1901-2005, as well as projections for 2006-2100 with a high emission scenario.

The researchers also considered how global warming might impact the odds of very extreme weather events occurring in the future.

“With every degree of warming it is the rarest and the most extreme events—and thereby the ones with typically the highest socio-economic impacts—for which the largest fraction is due to human-induced greenhouse gas emissions,” the authors concluded.

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--- Linda Carroll, NBC News contributor