Air Waves Trapped in Warmer Arctic Caused Extreme Weather

Extreme weather events, such as the heatwave that devastated crops and killed dozens in the U.S. in 2012, are becoming more frequent as a shift in the climate traps giant waves of air, researchers in Germany said.

The waves, which transport cold and warm air to Europe and the U.S., have become stuck twice as often since 2000 because of man-made global warming, researchers at the Potsdam Institute for Climate Impact Research said today in a statement. Meddling with these waves can exacerbate periods of unusual heat, they said.

“Evidence for actual changes in planetary wave activity was so far not clear,” said Stefan Rahmstorf, co-author of the study to be published in Proceedings of the National Academy of Sciences. “By knowing what patterns to look for, we have now found strong evidence for an increase in these resonance events.”

Climate change has moved up the political agenda in the U.S. after President Barack Obama made cutting climate-warming emissions a central goal of his second term.

When the so-called Rossby Waves, which are key climate regulators, wander across the globe, they suck warm air from the tropics to Europe, Russia, and the U.S. On their way back, they do the same with cold air from the Arctic. They’re increasingly trapped because the Arctic has been warming twice as fast as the rest of the globe, reducing the temperature difference that’s propelling the waves, the researchers said.

“The planetary waves topic illustrates how delicately interlinked components in the Earth system are,” said Hans Joachim Schellnhuber, head of the Potsdam institute. “It shows how disproportionately the system might react to our perturbations.”

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