Warming atmosphere is expanding the tropics, study finds

The globe’s tropics are expanding — and if you’re thinking coconuts and palm trees, don’t. Think deserts and drought. According to a new study in Science, satellite measurements show that the lowest level of the atmosphere in torrid subtropical regions on either side of the equator is heating up, and has pushed the northern and southern jet streams each some 70 miles closer to the poles since 1979. A continuation of the trend could deprive southern Europe of winter precipitation, expand deserts of the American Southwest, and nudge the Sahara Desert north, perhaps by hundreds of miles. “This may be a totally new aspect of climate change,” says study coauthor Thomas Reichler. The study authors conclude, “Regardless of the cause, the poleward shift of the jet streams and the associated subtropical dry zone, if it continues, could have important societal implications.” Indeed.