Arctic Melt Brings More Persistent Heat Waves to U.S., Europe

Ice Off the Coast of the Norwegian Fjord Kongsfjord
Sea-ice melt in the Arctic, Barents and Kara seas since 2004 has made more than twice as likely atmospheric circulations that suck cold Arctic air to Europe and Asia, a group of Japanese researchers led by the University of Tokyo’s Masato Mori said in a study published in 2014 in Nature Geoscience. Photographer: Martin Bureau/AFP via Getty Images

The U.S., Europe and Russia face longer heat waves because summer winds that used to bring in cool ocean air have been weakened by climate change, German researchers said.

Rapid Arctic warming disturbs air streams in ways that have “significantly” reduced summer storms, raising the likelihood of heat waves, the Potsdam Institute for Climate Impact Research said in a report Thursday in the journal Science. Hot weather in Russia in 2010 devastated crop harvests and caused wildfires.

“Unabated climate change will probably further weaken summer circulation patterns which could thus aggravate the risk of heat waves,” co-author Jascha Lehmann said in a statement e-mailed by the institute. “The warm temperature extremes we’ve experienced in recent years might be just a beginning.”

With heat-trapping gases from burning oil, coal and natural gas at record levels, global temperatures are set to warm by 3.6 degrees Celsius (6.5 Fahrenheit) by the end of the century, according to the International Energy Agency. That’s the quickest climate shift in 10,000 years. Temperature gains can disrupt air flows that govern storm activity, the Potsdam report showed.

“When the great air streams in the sky above us get disturbed by climate change, this can have severe effects on the ground,” lead author Dim Coumou said. The study used data on atmospheric circulation in the Northern Hemisphere from 1979 to 2013.

Warming in the Arctic, where temperatures rise faster than elsewhere as ice caps melt, is believed to narrow temperature differences and thus weaken the jet stream -- air motion that’s important for shaping our weather, according to the scientists.

“The reduced day-to-day variability that we observed makes weather more persistent, resulting in heat extremes on monthly timescales,” Coumou said. “The risk of high-impact heat waves is likely to increase.”

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