Climate change has made urban pollution more dangerous and thunderstorms more destructive.

https://www.bloomberg.com/news/articles/2019-02-19/summer-2019-climate-change-will-bring-strong-storms-and-smog?srnd=climate-changed

By Eric Roston
February 19, 2019, 3:00 AM EST

Air pollution is the sixth-biggest killer worldwide—more than alcohol use, kidney failure or too much salt. The cause, as we all know, is the burning of fossil fuels, which generates soot and other airborne particles that hang in the atmosphere.

In a new example of the vicious cycles spun up by climate change, research from the Massachusetts Institute of Technology suggests for the first time that pollution is lingering longer over cities and summer storms are becoming more powerful.

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The problem has to do with how the atmosphere’s changing heat structure, which is directly related to global warming, drives massive weather systems in regions where most people live. High in the atmosphere, these “extratropical cyclones” are powered by the mix of warm and cool air, and are the force behind blizzards, nor’easters and everyday thunderstorms. In cities, their winds typically blow away air pollution after a few smog-filled summer days. In the South, they keep powerful storms moving along. But that’s been changing.

While climate change has intensified hurricanes and made seas rise, the circulation of these huge weather systems has been weakening. The result is cities swathed for days in pollution and whole regions more vulnerable to sudden, torrential storms.

“Summertime weather isn’t ventilating American cities at the rate that it did in the past,” Gertler said.

Extratropical cyclones live off the temperature difference between southern and northern latitudes. As the Arctic warms, which it’s doing twice as fast as the global average, that difference is shrinking, and gradually restructuring weather in the hemisphere.

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The amount of energy available to thunderstorms is “increasing at a pretty significant rate,” or 13 percent, Gertler said, potentially making them stronger. That change, coupled with additional moisture in the atmosphere, is leading to more rainfall from short, intense bursts.

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