Massive solar and wind farms could bring vegetation back to the Sahara – and have other unforeseen consequences

A solar plant in Morocco, on the edge of the Sahara desert. Image: Getty.

Switching from fossil fuels to renewable energy is an important and necessary step towards averting climate change. However, in our efforts to go green, we also need to be mindful of other consequences, both intended and unintended – and that includes how a mass deployment of renewable technology might affect its surrounding climate.

What if the Sahara desert was turned into a giant solar and wind farm, for instance? This is the topic of new research published in the journal Science by Yan Li and colleagues. They found that all those hypothetical wind turbines and solar panels would make their immediate surroundings both warmer and rainier, and could turn parts of the Sahara green for the first time in at least 4,500 years.

The scientists behind the research looked at the maximum amount of solar and wind energy that could be generated in the Sahara desert and the transition region to its south, the Sahel. The two regions were picked as they are relatively plausible sites for such an enormous roll-out of renewable energy, being fairly near to substantial demand from Europe and the Middle East, while having limited other demands on the land. Both have substantial potential resources of wind and solar energy. Li and colleagues also suggest that the Sahel, in particular, could also benefit from economic development and more energy for desalination, providing water for cities and agriculture.

Africa has the greatest solar resource of any continent – by far. Image: SolarGIS/creative commons.

As the two regions are so large, the solar and wind farms that were simulated in this study are the size of entire countries – 38 times larger than the UK. They would be vastly bigger than any existing solar and wind farms, and could provide up to four times as much energy as is currently consumed globally.

This would prompt quite significant changes in the local environment – massive wind farms would raise temperatures by around 2 degrees for instance, similar to the amount of global warming we are concerned about. Solar would cause a smaller temperature change, around 1 degrees.


Precipitation increases of 0.25 mm per day associated with wind farms sound more modest, yet this would be almost double the previous amount of rainfall. Again, the effect associated with solar parks was smaller – an increase of 0.13 mm/day – but still significant when added up over a year.

Why turbines and panels mean warmth and rain

Wind farms largely cause temperature increases because their turbine blades bring warmer air down to the surface, especially at night. This has been observed in field studies and using remote sensing. They have also been shown to increase moisture in the air.

Solar panels mean more solar radiation is absorbed and less of the sun’s energy is reflected back into space. This causes the land surface to warm up. Several studies have shown this, including one which showed that the effect of warming caused by fossil fuels, via carbon emissions, was 30 times greater than the warming caused by solar photovoltaics absorbing more solar radiation. However, temperature effects may vary within the solar park and with season.

In the Sahara simulation, extra rainfall happens because wind turbines represent an obstacle to free-flowing air, slowing it down and reducing the effect of the Earth spinning on air flow. This lowers the air pressure, and the difference in pressure between the Sahara and surrounding areas causes wind to flow there. When the air meets, or converges, in the Sahara it has nowhere else to go but up. As the air rises, water vapour in it condenses and rain drops form.

For solar, the process is slightly different: warmer air, heated by the panels, simply rises. However, this also promotes low pressure, causing air to flow there, converge and rise.

Large-scale wind and solar would mean more new rain in some areas than others. Image: Eviatar Bach/creative commons.

More rainfall also means more vegetation. This increases surface roughness, as with wind turbines, and causes more solar radiation to be absorbed, as with solar panels. This reinforcing cycle is known as a “climate feedback” and incorporating these vegetation feedbacks is a novel aspect of the research by Li and colleagues.

Time to make it a reality?

Not quite. Decisions aren’t made in response to environmental impacts alone – if this was the case we’d have already ditched fossil fuels. It’s certainly true that developing a mega renewable energy site across the Sahara and the Sahel would be a game-changer, but there are lots of other factors to consider first.

These areas may be sparsely populated but people do live there, their livelihoods are there, and the landscapes are of cultural value to them. Can the land really be “grabbed” to supply energy to Europe and the Middle East?


Coherent and stable energy policies are challenging enough within an individual nation, let alone between nations with all the potential political implications and energy security issues this implies. Though mass amounts of cheap Saharan energy sounds like a great thing, it is not clear it would be a secure enough investment for the economics to add up.

It’s also hard to tell what this would mean for desertification, which is caused by poor land management, such as overgrazing, as well as by the climate. The changes to rainfall looked at in this study are regional, not global, and once the wind and solar farms were taken away their effects would disappear and the land could revert back to its previous state.

Overall, this is an interesting and important piece of research, highlighting the need to be mindful of unintended consequences, be these positive or negative, of the energy transition. Integrating these findings with other social, economic, environmental and technical considerations is essential to ensure we don’t leap from the frying pan into the fire.

The Conversation

Alona Armstrong, Senior lecturer, Lancaster University.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

 
 
 
 

CityMetric is now City Monitor! Come see us at our new home

City Monitor is now live in beta at citymonitor.ai.

CityMetric is now City Monitor, a name that reflects both a ramping up of our ambitions as well as our membership in a network of like-minded publications from New Statesman Media Group. Our new site is now live in beta, so please visit us there going forward. Here’s what CityMetric readers should know about this exciting transition.  

Regular CityMetric readers may have already noticed a few changes around here since the spring. CityMetric’s beloved founding editor, Jonn Elledge, has moved on to some new adventures, and a new team has formed to take the site into the future. It’s led by yours truly – I’m Sommer Mathis, the editor-in-chief of City Monitor. Hello!

My background includes having served as the founding editor of CityLab, editor-in-chief of Atlas Obscura, and editor-in-chief of DCist, a local news publication in the District of Columbia. I’ve been reporting on and writing about cities in one way or another for the past 15 years. To me, there is no more important story in the world right now than how cities are changing and adapting to an increasingly challenging global landscape. The majority of the world’s population lives in cities, and if we’re ever going to be able to tackle the most pressing issues currently facing our planet – the climate emergency, rising inequality, the Covid-19 pandemic ­­­– cities are going to have to lead the way.

That’s why City Monitor is now a global publication dedicated to the future of cities everywhere – not just in the UK (nor for that matter just in the US, where I live). Our mission is to help our readers, many of whom are in leadership positions around the globe, navigate how cities are changing and discover what’s next in the world of urban policy. We’ll do that through original reporting, expert opinion and most crucially, a data-driven approach that emphasises evidence and rigorous analysis. We want to arm local decision-makers and those they work in concert with – whether that’s elected officials, bureaucratic leaders, policy advocates, neighbourhood activists, academics and researchers, entrepreneurs, or plain-old engaged citizens – with real insights and potential answers to tough problems. Subjects we cover include transportation, infrastructure, housing, urban design, public safety, the environment, the economy, and much more.

The City Monitor team is made up of some of the most experienced urban policy journalists in the world. Our managing editor is Adam Sneed, also a CityLab alum where he served as a senior associate editor. Before that he was a technology reporter at Politico. Allison Arieff is City Monitor’s senior editor. She was previously editorial director of the urban planning and policy think tank SPUR, as well as a contributing columnist for The New York Times. Staff writer Jake Blumgart most recently covered development, housing and politics for WHYY, the local public radio station in Philadelphia. And our data reporter is Alexandra Kanik, whose previous roles include data reporting for Louisville Public Media in Kentucky and PublicSource in Pittsburgh, Pennsylvania.

Our team will continue to grow in the coming weeks, and we’ll also be collaborating closely with our editorial colleagues across New Statesman Media Group. In fact, we’re launching a whole network of new publications, covering topics such as the clean energy transition, foreign direct investment, technology, banks and more. Many of these sectors will frequently overlap with our cities coverage, and a key part of our plan is make the most of the expertise that all of these newsrooms combined will bring to bear on our journalism.

Please visit citymonitor.ai going forward, where you can also sign up for our free email newsletter.


As for CityMetric, some of its archives have already been moved over to the new website, and the rest will follow not long after. If you’re looking for a favourite piece from CityMetric’s past, for a time you’ll still be able to find it here, but before long the whole archive will move over to City Monitor.

On behalf of the City Monitor team, I’m thrilled to invite you to come along for the ride at our new digs. You can follow City Monitor on LinkedIn and on Twitter. If you’re interested in learning more about the potential for a commercial partnership with City Monitor, please get in touch with our director of partnerships, Joe Maughan.

I want to thank and congratulate Jonn Elledge on a brilliant run. Everything we do from here on out will be building on the legacy of his work, and the community that he built here at CityMetric. Cheers, Jonn!

To our readers, on behalf of the City Monitor team, thank you from all of us for being such loyal CityMetric fans. We couldn’t have done any of this without you.

Sommer Mathis is editor-in-chief of City Monitor.