Jet stream shift is expanding the Earth's tropics and deserts

USATODAY.com : "By Andrew Bridges, Associated Press Writer

WASHINGTON — Deserts in the American Southwest and around the globe are creeping toward heavily populated areas as the jet streams shift, scientists reported Thursday.

The result: Areas already stressed by drought may get even drier.

Satellite measurements made from 1979 to 2005 show that the atmosphere in the subtropical regions both north and south of the equator is heating up. As the atmosphere warms, it bulges out at the altitudes where the northern and southern jet streams slip past like swift and massive rivers of air. That bulging has pushed both jet streams about 70 miles closer to the Earth's poles.

Since the jet streams mark the edge of the tropics, in essence framing the hot zone that hugs the equator, their outward movement has allowed the tropics to grow wider by about 140 miles. That means the relatively drier subtropics move as well, pushing closer to places like Salt Lake City, where Thomas Reichler, co-author of the new study, teaches meteorology.

'One of the immediate consequences one can think of is those deserts and dry areas are moving poleward,' said Reichler, of the University of Utah. Details appear in Thursday's Science Express, the online edition of the journal Science."