Thursday, June 01, 2017

Warming Could Push Earth’s Rains Northward

This sign at a lake in the Turfan Basin of far western China reads "No Swimming," but the lake has dried up completely within the past decade as the planet has warmed and precipitation has shifted away from this region. Click image to enlarge. (Credit: Aaron E. Putnam) Click to Enlarge.
The Earth’s rising temperature is expected to knock the global water cycle out of whack, but exactly how it will change is uncertain.  Scientists, though, can look for clues as to what the future might bring in the major climate swings that have happened in the past.

A new study that does just that suggests that Earth’s rain belts could be pushed northward as the Northern Hemisphere heats up faster than the Southern Hemisphere.  That shift would happen in concert with the longstanding expectation for already wet areas to see more rain and for dry ones to become more arid.

The study, detailed Wednesday in the journal Science Advances, “adds to the large body of evidence that climate change is going to mess with the large-scale motions of air and water in the atmosphere.  And this matters, because those patterns largely determine where it's rainy or arid, broadly speaking,” NASA climate scientist Kate Marvel, who wasn’t involved with the study, said in an email.

These changes in rain distribution could have implications for future water resources, particularly in areas where water supplies are already stressed, such as the western U.S. and parts of Africa.

From the basic physics of the atmosphere, scientists expect that as the planet heats up from ever-mounting levels of greenhouse gases, net global precipitation will increase because a warmer atmosphere holds more moisture.  But that increase won’t be uniform and is likely to be concentrated in the already moist tropics.  And because higher temperatures also increase evaporation, other areas, such as the already dry subtropics, are likely to dry out further.

Read more at Warming Could Push Earth’s Rains Northward

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