From floods in Pakistan to droughts in China and tornadoes in the U.S., the past few years have seen numerous deadly extreme weather events. A team of climate scientists at the Potsdam Institute for Climate Impact Research in Germany laid the blame for the increased frequency of disasters on a warming climate.
"The question is whether these weather extremes are coincidental or a result of climate change," said Dim Coumou, lead author of the Potsdam Institute's analysis, in a press release. "Global warming can generally not be proven to cause individual extreme events -– but in the sum of events the link to climate change becomes clear."
"It is not a question of yes or no, but a question of probabilities," said Coumou.
"It's like a game with loaded dice," he reported in the journal Nature Climate Change. "A six can appear every now and then, and you never know when it happens. But now it appears much more often, because we have changed the dice."
The climatologists' analysis started with some basic physics. Warm air holds more water and carries the potential to pack a more ferocious punch when a storm forms. Statistical trends in temperature and precipitation records showed the scientists that a warmer climate was indeed associated with more intense storms and extreme droughts. Computer simulations also reflected the connection between storms and climate change.
"Single weather extremes are often related to regional processes, like a blocking high pressure system or natural phenomena like El Niño," said article co-author Stefan Rahmstorf. "These are complex processes that we are investigating further. But now these processes unfold against the background of climatic warming.”
“That can turn an extreme event into a record-breaking event," said Rahmstorf.
Photo: Chief Yeoman Mike Shea helps a crane operator move a wrecked vehicle during tornado clean-up efforts in Joplin, Mo. Credit: Wikimedia Commons, U.S. Navy photo by Lt. j.g. Ryan Sullivan/Released.