The Sahara. The very name evokes an endless, forbidding landscape of arid desert with undulating dunes and no sign of vegetation, or even life.
But we may soon make it rain in the planet’s largest desert, scientists say. Better yet: increased precipitation, which could bring some of the greenery back to the Sahara, would be thanks to renewable energy sources like wind and solar that are being installed in parts of the inhospitable desert.
“Energy generation by wind and solar farms could reduce carbon emissions and thus mitigate anthropogenic climate change,” a team of scientists who conducted experiments using a climate model write in a paper published in the journal Science.
“[T]he installation of large-scale wind and solar power generation facilities in the Sahara could cause more local rainfall, particularly in the neighboring Sahel region,” they explain. “This effect, caused by a combination of increased surface drag and reduced albedo, could increase coverage by vegetation, creating a positive feedback that would further increase rainfall.”
The vast North African desert is seen as an ideal site for solar and wind energy generation because it is sundrenched and windswept all year round. It also has endless vistas of available space, seeing as it is unsuitable for agriculture and remains sparsely populated. Energy generated there from renewables could be fed into local grids and, thanks to the Sahara’s proximity to Europe, into European grids.
“Solar and wind power projects in Africa and the Middle East are already underway, from Morocco to Dubai to Ethiopia, including over 200 GW of solar power planned by 2030,” says the study’s co-author Jorge Rivas, a political scientist. “This renewable electricity could be transported to regions a few thousand kilometers away, and long-distance transmission lines have already existed in Africa and elsewhere for decades.”
Wind and solar farms are known to have the capacity to impact local weather conditions like heat and humidity. And the larger the instillations, the more marked these effects can be, especially in places with extreme weather conditions like the Sahara.
“Our model results show that large-scale solar and wind farms in the Sahara would more than double the precipitation in the Sahara, and the most substantial increase occurs in the Sahel, where the magnitude of rainfall increase is between ~200 and ~500 mm per year,” observes the study’s first author, Yan Li, a scientist at the University of Illinois at Urbana-Champaign in the US. “As a result, vegetation cover fraction increases by about 20 percent.”
Wind turbines facilitate the vertical mixing of heat in the air, whereby warmer air at higher altitudes is pushed down to the surface. The result is an increase in land surface friction, which causes an increase in the chances of precipitation. “This increase in precipitation, in turn, leads to an increase in vegetation cover, creating a positive feedback loop,” Li says.
Simultaneously, large banks of solar panels help absorb much of the sun’s rays, thereby reducing the amount of light reflected off the Earth’s surface in a phenomenon known as albedo. This, too, increases the likelihood of more precipitation.
“This research certainly suggests that it will be possible to create a self-sustaining renewable energy system, which will be greatly beneficial for the socioeconomic development of the region,” explains Jagadish Shukla, a prominent Indian climate scientist who did not participate in the study.
“The Sahara has been expanding for some decades, and solar and wind farms might help stop the expansion of this arid region,” adds Russel R. Dickerson, a scientist at the Department of Atmospheric and Oceanic Science at the University of Maryland. “This looks like a win-win to me.”
