Wind and solar farms 'could increase Sahara rainfall', report says

Rain levels in the Sahara Desert could be boosted by installing massive wind and solar farms that could also help slow global warming, researchers said on Thursday.

Researchers believe that changes to the desert climate caused by such a huge project could cause more plants would grow near where the farms are placed.

"The increase in rainfall and vegetation, combined with clean electricity as a result of solar and wind energy, could help agriculture, economic development and social well-being in the Sahara, Sahel, Middle East and other nearby regions," said co-author Safa Motesharrei, a researcher at the University of Maryland.

Scientists used computer modelling to simulate the effect of covering 20 percent of the world's largest desert with solar panels and installing three million wind turbines there, the report published in the journal Science said.

A solar and wind farm of that size - more than 3.5 million square miles (nine million square kilometers) - would be "at a scale large enough to power the entire world", the report said.

According to model simulations, the wind and solar farm effect boosted average rain across the entire Sahara from 0.24 millimeters per day to 0.59 mm per day.

The most substantial rain increase could be in the Sahel, a semi-arid region extending from Senegal to Sudan, where residents could see 200 to 500 mm more rain per year, or about 1.12 mm per day near the wind farms.

The report said this would be "large enough to have major ecological, environmental, and societal impacts".

While this would boost the growth of vegetation in some areas, most of the desert would remain largely unchanged.

"The vast majority of the Sahara would remain extremely dry," said co-author Daniel Kirk-Davidoff, an adjunct associate professor at the University of Maryland.

But more rain along the southern edge of the Sahara would lead to more plant growth, "which would allow for more grazing", he told AFP in an email.

"It is hard to imagine that this would be a bad thing from the point of view of human communities there."

Wind farms have the potential to bring in warmer air from above, particularly at night, causing a process which can increase evaporation and plant growth.

This warm air exchange can also double the amount of daily precipitation.

Meanwhile, dark-coloured solar panels reduce the amount of surface light that is reflected from the Earth, slightly raising temperatures and also triggering more precipitation.

Previous studies have found that wind and solar farms can introduce significant changes in climate at the continental scale by creating rougher, darker land surfaces.

But this study is the first to incorporate how vegetation would change as a result, said lead author Yan Li, a postdoctoral researcher at the University of Illinois.

"The lack of vegetation feedbacks could make the modeled climate impacts very different from their actual behaviour."

Researchers also pointed out that any hikes in temperature from solar and wind farms would be limited in geographic area and scope, unlike fossil fuel emissions which continually build in the atmosphere and raise warming over time.