C’est pas le tout de réchauffer le climat : l’évaporation de l’eau de toute la planète va être plus importante que prévue.
Une broutille : 30% de l’eau disponible
Drought at Lake Hume. Image: Flickr
Sure, scientists expect the changing climate to bring on more drought. There’s going to be less rainfall in already arid regions, that’s fairly certain. And that alone would be bad news for denizens of the planet’s dry zones—in some places in North Africa, the American Southwest, India, and the Middle East, water shortages could well become an existential threat to civilization. But new research shows that evaporation may be more of a problem than previously thought: Climate change could dry out up to a third of the planet.
The study, published in the journal Climate Dynamics last month, estimates that climate change will cause reduced rainfall alone to dessicate 12 percent of the Earth’s land by 2100. But if evaporation is factored in, the study’s authors say that it will "increase the percentage of global land area projected to experience at least moderate drying by the end of the 21st century from 12 to 30 percent."
“We know from basic physics that warmer temperatures will help to dry things out,” the study’s lead author, Benjamin Cook, a climate scientist with Columbia University and NASA’s Goddard Institute for Space Studies, said in a statement. “Even if precipitation changes in the future are uncertain, there are good reasons to be concerned about water resources.”
Writing in a 2011 literature review in the science journal Nature, the physicist Joe Romm elaborates on how increased heat and evaporation can lead to a vicious cycle: "Precipitation patterns are expected to shift, expanding the dry subtropics. What precipitation there is will probably come in extreme deluges, resulting in runoff rather than drought alleviation. Warming causes greater evaporation and, once the ground is dry, the Sun’s energy goes into baking the soil, leading to a further increase in air temperature."
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