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.

 
 
 
 

The Fire Brigades Union’s statement on Theresa May’s resignation is completely damning

Grenfell Tower. Image: Getty.

Just after 10 this morning, Theresa May announced that she would resign as Britain’s prime minister on 7 June. A mere half an hour later, a statement from Royal Institute of British Architects president Ben Derbyshire arrived in my inbox with a ping:

“The news that Theresa May will step down as Prime Minister leaves the country in limbo while the clock ticks down to the latest deadline of 31 October. While much is uncertain, one thing remains clear – a no deal is no option for architecture or the wider construction sector. Whoever becomes the next Prime Minister must focus on taking the country forward with policies beyond Brexit that tackle the major challenges facing the country such as the housing crisis and climate change emergency.”

I was a bit baffled by this – why would the architecture profession try to get its thoughts into a political story? But then Merlin Fulcher of Architects Journal put me right:

Well you know construction is a larger contributor to GDP than financial services, and most of the work UK architects do is for export, and at least half of the largest practice (Foster + Partners) are EU, so there's a lot at stake

— Merlin Fulcher (@merlinfulcher) May 24, 2019

So, the thoughts of the RIBA president are an entirely legitimate thing to send to any construction sector-adjacent journalists who might be writing about today’s big news, and frankly I felt a little silly.

Someone else who should be feeling more than a little silly, though, is Theresa May herself. When listing her government’s achievements, such as they were, she included, setting up “the independent public inquiry into the tragedy at Grenfell Tower” – a fire in a West London public housing block in June 2017 – “to search for the truth, so nothing like it can ever happen again, and so the people who lost their lives that night are never forgotten”.

Matt Wrack, general secretary of the Fire Brigades Union, is having precisely none of this. Here’s his statement:

“Many of the underlying issues at Grenfell were due to unsafe conditions that had been allowed to fester under Tory governments and a council for which Theresa May bears ultimate responsibility. The inquiry she launched has kicked scrutiny of corporate and government interests into the long-grass, denying families and survivors justice, while allowing business as usual to continue for the wealthy. For the outgoing Prime Minister to suggest that her awful response to Grenfell is a proud part of her legacy is, frankly, disgraceful.”

A total of 72 people died in the Grenfell fire. At time of writing, nobody has been prosecuted.

Jonn Elledge is editor of CityMetric and the assistant editor of the New Statesman. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.

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