Climate change could transform one of Africa's driest regions, the Sahel, into a very wet one, a study showed Wednesday. But this is not necessarily good news.
While there would be more water for farming and grazing, the region may also face devastating storms and floods for which it is completely unprepared.
"The sheer size of the change is mindboggling," said Anders Levermann from the Potsdam Institute for Climate Impact Research (PIK) who co-authored the study in the journal Earth System Dynamics.
"Once the temperature approaches the threshold, the rainfall regime could shift within just a few years," he said in a statement.
Levermann and his team used computer simulations to project the Sahel's climate future.
They found that beyond 1.5 to 2.0 degrees Celsius of global warming over pre-industrial levels, the region's rainfall will change. This is also the warming ceiling targeted in the 2015 Paris Agreement.
"Although this tipping point is potentially beneficial, the change could be so big it would be a major adaptation challenge for an already troubled region," said a PIK statement.
The real-life impacts are hard to predict.
In April, a different study said the Sahel has seen a three-fold increase since 1982 in destructive rainstorms that bring misery rather than relief.
The researchers found that destructive storms known to meteorologists as "mesoscale convective systems" (MCS) grew in frequency from about 24 per rainy season in the early 1980s, to about 81 today.
The rainy season lasts from about June to September.
Caught between drought and flood
In the Sahel, MCS events are "some of the most explosive storms in the world", the researchers said.
These storms supply about 90 percent of the region's rainfall—but more tempests do not equate to more water. Water from violent storms tends to run off and not filter into the soil where crops can benefit.
It also washes away nutrient-holding agricultural soil in a region still recovering from a historic 20-year drought between the 1970s and 1990s.
"The enormous change that we might see would clearly pose a huge adaptation challenge to the Sahel," Levermann said of the future.
"From Mauritania and Mali in the west to Sudan and Eritrea in the east, more than 100 million people are potentially affected that already now are confronted with a multifold of instabilities, including war."
As the tipping point approaches, the Sahel may experience years of "hard-to-handle variability" between drought and flood, he said.
"The dimension of the change calls for urgent action."
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Jacob Schewe et al. Non-linear intensification of Sahel rainfall as a possible dynamic response to future warming, Earth System Dynamics (2017). DOI: 10.5194/esd-8-495-2017 , doi.org/10.5194/esd-8-495-2017