Global warming brews weird weather: Human influence on extreme heat and rain events is growing.



Cathal McNaughton/Reuters/Corbis

Global warming brews weird weather: Human influence on extreme heat and rain events is growing.

Quirin Schiermeier 27 April 2015

Climate change will increase the risk of extreme precipitation, such as storms that cause flooding. Global warming has profoundly changed the odds of extreme heat, rain and snowfall, researchers report on 27 April in Nature Climate Change1. Climate change caused by human activities currently drives 75% of daily heat extremes and 18% of heavy rain or snowfall events, the team found — warning that further global warming will sharply increase the risks of such weather. The researchers looked at ‘moderate’ extremes, which they defined as events expected to occur on 1 in every 1,000 days under present conditions. “Climate change doesn’t ’cause’ any single weather event in a deterministic sense,” says Erich Fischer, a climate scientist at the Swiss Federal Institute of Technology in Zurich (ETH Zurich), Switzerland, and the study’s lead author. “But a warmer and moister atmosphere does clearly favour more frequent hot and wet extremes.” The researchers found that local variations in weather are already large, even though the global average temperature has risen by just 0.85 °C since the start of the Industrial Revolution. This finding agrees with earlier research on climate and weather extremes. A paper published in Nature in 2011, for example, found that climate change has already doubled the risk of the atmospheric conditions that produced catastrophic floods in England and Wales in 20002; an earlier study found the same result for the conditions that triggered a massive European heat wave in 20033. And human influence on the ‘moderate’ extremes examined in Fischer’s study is set to increase with every degree that the temperature rises, finds the analysis. If the world were to warm by 2 °C above the pre-industrial level, human-caused climate change would drive 40% of rain and snow extremes and 96% of heat extremes, the researchers found….

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