As warming continues, ‘hot #drought’ becomes the norm, not an exception — #NewMexico Political Report #aridification

West Drought Monitor May 15, 2018.

From the New Mexico Political Report (Laura Paskus):

“Climate change for the Southwest is all about water,” said Jonathan Overpeck, who has spent decades studying climate change and its impacts in the southwestern United States. Warming affects the amount of water flowing in streams, and the amount of water available to nourish forests, agricultural fields and orchards. There’s also the physics of the matter: A warmer atmosphere holds more moisture, demanding more from land surfaces. Plants need more water, too. “Any way you look at it,” Overpeck said, “water that normally would flow in the river or be in the soil ends up instead in the atmosphere.”

[…]

Past southwestern droughts were notable for declines in precipitation. But today’s droughts are different, he explained. Even in wet years, which will still occur as the climate changes, warmer conditions dry out the landscapes.

“With atmospheric warming, we’re getting what we’re calling ‘hot droughts’ or ‘hotter droughts,’” he said. “That means that they’re more and more influenced by these warm temperatures, and the warm temperatures tend to make the droughts more severe because they pull the moisture out of plants, they pull the moisture out of rivers and out of soil—and that moisture ends up in the atmosphere instead of where we normally like to have it.”

From 1952 until 1956, below-normal rainfall caused “critical water deficiencies in much of the southern half of the Nation,” according to a 1965 U.S. Department of the Interior report. The 1950s drought had widespread impacts on New Mexico’s communities and economy. Today’s drought conditions, which Overpeck explains have been moving around the Southwest for 19 years, are exacerbated by warmer temperatures. The global temperature is 1.8 degrees Fahrenheit higher than it was in 1880, and the Southwest is warming at an even faster rate.

“What we’re seeing now in the drought that’s going on is that it’s more due to temperature increase and less due to precipitation deficit,” he said. And “hot drought” is what we should prepare to face in the future, too.

“More and more so, the droughts will really be defined by hotness, by warm temperatures that just suck the moisture out of the soil, suck the moisture out of our rivers,” he said. “And leaves the droughts an ever more devastating manifestation.”

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