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A Scientist Dreams Up A Plan To Stop The Sahara From Expanding

Sep 9, 2018
Originally published on September 11, 2018 8:21 am

The Sahara desert is expanding, and has been for at least a century. It's a phenomenon that seems impossible to stop.

But it hasn't stopped at least one group of scientists from dreaming of a way to do it. And their proposed solution, a grand scheme that involves covering vast areas of desert with solar panels and windmills, just got published in the prestigious journal Science.

Eugenia Kalnay, a prominent atmospheric scientist at the University of Maryland, has been thinking about this idea for a decade. Kalnay is small in stature, soft-spoken. But she's made her name with big and bold ideas. And what could be bigger and bolder than reversing the course of the world's biggest desert?

Her academic adviser at MIT, Jule Charney, was among the first to describe the vicious cycle that can lead to desertification. With drought, green vegetation disappears, and the light-colored dirt that remains reflects more of the sun. This cools the land surface, which in turn means that there's less heat driving air upward into higher and cooler levels of the atmosphere – the process that normally produces precipitation. So there's less rain, killing even more vegetation.

Kalnay wondered if there might be a way to revive those atmospheric currents. "It occurred to me that the same [cycle] would go in the opposite way, so it would increase precipitation, and vegetation, and then more precipitation," she says.

And then she thought of solar panels. They're dark, so they don't reflect the sun's light. Could they heat up the surface and revive those rain-bringing air currents?

Kalnay convinced one of her post-doc researchers to create a computer simulation of an otherworldly Sahara where 20 percent of the land is covered with solar panels. The computer model also turned the desert into a giant wind farm, covered with turbines. Kalnay thought they might also help boost those beneficial air currents.

And the simulation turned out just the way she'd hoped. It showed rainfall increasing by enough to bring back vegetation. The model showed the biggest increases in rainfall along the southern edge of the Sahara, the area called the Sahel.

"It is wonderful!" she says, and her eyes go wide with an infectious joy. "We were so happy because it seems like a major solution for some of the problems that we have."

The super solar farm she imagines is huge, as big as the entire United States. And it would generate four times as much electricity as the entire planet consumes right now. Kalmay talks of novel high-capacity transmission lines delivering power to Europe and the rest of Africa.

I told her that the whole scenario sounds like science fiction. Kalnay disagreed. "It would be science fiction if the technology was not available," she said.

"So you could imagine it?"

"Yes," she said, confidently.

After all, she's used to imagining the workings of the entire planet's atmosphere.

A few billion solar panels and windmills in the desert? No big deal.

A number of investors have explored the possibility of large solar farms in the Sahara, though nowhere near as massive as the scenario that Kalnay has simulated. Those ideas, however, remain stuck on drawing boards.

Copyright 2018 NPR. To see more, visit http://www.npr.org/.

RACHEL MARTIN, HOST:

A scientist hopes she has discovered a way to stop the spread of the Sahara Desert. Cycles of drought make the expanding desert seem unstoppable. But the journal Science published a researcher who refused to accept that. NPR's Dan Charles reports.

DAN CHARLES, BYLINE: At the University of Maryland, tucked away in the back corner of the computer science building, there's a scientist who's small in stature and soft-spoken. But her ideas are big and bold.

EUGENIA KALNAY: I am quite a famous scientist. I got basically all the top prizes.

CHARLES: Eugenia Kalnay studies how Earth's atmosphere works. And she's had this idea for how to stop more and more of Africa from turning into desert.

KALNAY: Actually, the idea came to me about 10 years ago.

CHARLES: She knew there's a vicious cycle at work in the Sahara. With drought, green vegetation disappears, and the light-colored dirt that remains reflects more of the sun. And that shuts down the rising air currents that lead to rain. Kalnay thought, maybe there's a way to revive those atmospheric currents.

KALNAY: It occurred to me that the same mechanism would go in the opposite way, so it will increase the precipitation and the vegetation - and then more precipitation.

CHARLES: Since the problem was that light-colored dirt and sand reflecting the sun, she'd need something dark instead. But what dark thing would you want covering huge areas of the desert? Well, solar panels. Kalnay convinced one of her postdoc researchers to create a computer simulation of an otherworldly Sahara, where 20 percent of the land is covered with solar panels - also windmills. Kalnay thought they might also help the air currents. And the simulation turned out just the way she wanted. It showed rainfall increasing enough to bring back vegetation, especially along the southern edge of the Sahara, the area called the Sahel.

KALNAY: It is wonderful. We were so happy because it seems like a major solution for some of the problems that we have.

CHARLES: This super solar farm she imagines is huge, as big as the entire United States, generating four times as much electricity as the entire planet consumes right now. I told her it seems like science fiction.

Does it seem like science fiction to you?

KALNAY: I don't think so. It would be science fiction if the technology was not available.

CHARLES: So you could imagine it?

KALNAY: Yes.

CHARLES: After all, she's used to imagining the workings of the entire planet's atmosphere. A few billion solar panels and windmills in the desert? No big deal.

Dan Charles, NPR News. Transcript provided by NPR, Copyright NPR.