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.

 
 
 
 

Does it matter that TfL are renaming White Hart Lane station Tottenham Hotspur?

New White Hart Lane. Image: Getty.

Pretend for a moment that you’re travelling in the London of 1932. You’re taking the Piccadilly Line northbound and alight at Gillespie Road station. The name should be obvious: it’s inscribed in bespoke brown tiling on the platform.

But that 31 October, following an intense campaign by the eponymous football club, the London County Council changed the station’s name to Arsenal (Highbury Hill). The area’s growing association with the name “Arsenal” ended in a lengthy negotiation that changed maps, signs and train tickets alike. Football had acquired so much power that it changed the name of not just a Tube station but an entire suburb, even before the era of Wenger or the Emirates.

Now the spectre of name changes is on the horizon once again. As Tottenham Hotspur FC inches closer to completing its new stadium, the club is clamouring for a renamed Overground station. Despite the fact the new stadium is located on almost exactly the same site as the old just off White Hart Lane, and fans have long been calling the scaffolding-laden mess “New White Hart Lane”, the club’s executive director is adamant that the station’s existing name cannot stand. White Hart Lane station, on the Overground line leaving Liverpool Street, is set to be renamed “Tottenham Hotspur”, at a cost to the club of £14.7m.

Little has been made of the fact that this peculiar PR kerfuffle is tied to Spurs’ failure to convince Nike to sponsor the venue. Some sources have even claimed that the sponsorship is yet to be finalised because it is somehow contingent on the renaming of the Overground station; beyond the ridiculous Johnson-era vanity project that was the Emirates Air Line, it seems improbable that TfL will allow any more corporate-flavoured information pollution. There will be no “Nike Stadium” station on the way to Enfield, much as there is no “Emirates” on the way to Cockfosters, especially if public consultation gets a look in.

The scene of the crime. Image: TfL.

But there’s a problem with the new name, all the same. “White Hart Lane” already means “football stadium”, in the same way Loftus Road or Stamford Bridge do. Changing it to “Tottenham Hotspur” risks opening the floodgates to an “O2 North Greenwich” or a “Virgin Euston” at some point in future, names as banal as there are dystopian. The Greater London Authority has promised to spend the £14.7m fee on community programmes in the local area – but that’s not much money to set the precedent that a private company can mess about with the Tube map.


What’s more, as CityMetric has often observed, there are plenty of station names across London that could do with a tidy up. Picking one that’s perfect already and asking for £14.7m to change it is adding insult to injury. How much would it cost a community group if they asked to change the name of Goodge Street to Fitzrovia? Why does a vast corporate entity backed by international sponsors and thousands of season ticket holders get to set the standard?

Back in Arsenal’s day, changing names on the Tube must have been easy; changes could be accommodated gradually without bothering the every day traveller. But in our world of online information, maps and apps, name changes are rather more complicated.

The question is – if TfL can bring itself to balefully accept this particular proposition, why can’t it accept ours? Why sort out a single non-issue on the Tube Map when you can catch lots of real ones in one go? A day’s pandemonium might just be a price worth paying to fix the Bethnal Greens problem once and for all.