A shifting storm track to the northern latitudes of the U.S. is expected to leave the Southwest increasingly parched during the spring season, according to a new study published in Geophysical Research Letters and covered by Scientific American August 20.

Since 1978, the jet stream that brings Pacific storms onshore has been shifting northward. The result: less rain and snow in the American Southwest.

Why is the jet stream shifting northward? It turns out that carbon dioxide emissions have warmed the lower portions of the atmosphere, and human-produced chemicals have eaten holes in the ozone layer, cooling the upper reaches of Earth’s atmosphere. The difference in atmospheric pressures has driven jet streams in both the northern and southern hemispheres closer to the poles. And it’s all happened since the 1980s.

“It’s man-made either way you look at it,” Joellen Russell, a senior author of the study, said in the Scientific American article.

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