Summer heatwaves and downpours have become more frequent in the northern hemisphere this century, apparently because extreme weather can get trapped for weeks in the same place in a warming world, a study showed on Monday. Disruptions to the jet stream, which forms huge meandering waves as it blows at high altitude around the planet, and cold air from a thaw of Arctic ice may explain why weather systems are stalling more often, the scientists wrote. “Weather extremes in the summer - such as a record heatwave in the United States that hit corn farmers and worsened wildfires in 2012 - have reached an exceptional number in the last 10 years,” the Potsdam Institute for Climate Impact Research said of its findings. Other long-lasting extremes include a 2010 heatwave in Russia and floods in Pakistan, a 2003 heatwave in Europe and rains that caused flooding of the Elbe and Danube Rivers in Europe in 2002, it said.

“We are warming our atmosphere by emitting carbon dioxide from fossil fuels, but the increase in devastating heatwaves in regions like Europe or the U.S. seems disproportionate,” lead author Dim Coumou said in a statement.