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.

 
 
 
 

Do South Hampshire deserve its own metro mayors?

Portsmouth. Image: Getty.

The idea of metro mayors is a good idea. So good, in fact, I think is should be brought to other conurbations, such as the south coast cities of Southampton, Portsmouth and Brighton.

Greater Brighton has already got the idea in motion – although it needs more momentum to make it happen and democratise it. The question is what changes in Hampshire are needed for a Greater Southampton or a Greater Portsmouth to exist?

A small bit of backstory. The government had an idea a few years ago to create a Solent City deal, which included South Hampshire and Isle of Wight. The plan fell flat because Hampshire County Council blocked it.

Hampshire today. Image: Wikimedia Commons.

This was the right thing to do in my opinion. The government’s ambition was to rope together a very diverse area with no clear economic heart – it was always going to be a bad idea. Giving the region an extra few million pound a year may have sounded good for strapped for cash councils in the area, but would have met with a lot of opposition and resentment from locals.

Redrawing the county map

I don't ask for much, just to drastically re-shape Hampshire. Image: author provided.

In order to make this happen, Hampshire's county council should be dismantled and all the councils in the county turned into unitary authorities. Various Hampshire councils have applied to create a Southampton City Region, to qualify for transport funding – but the current proposal doesn't include Romsey and Winchester.

This to me is short sighted and arrogant on Hampshire's part. It’s come about in part because Hampshire doesn't want to lose its "capital", but also because these are wealthy areas and they'd rather they weren’t mixed up with the sorts that live in Soton. We should bin that sort of attitude.

The proposed Southampton City Region. Image: author provided.

Much like Southampton, there is a desire for more cross-border partnership in the Portsmouth City Region (PCR), too. Most of the boroughs are established, though I’d favour a tiny bit of adjustment to create a Waterlooville borough and enlarge Fareham slightly. All that’s necessary requires is the breaking up of Winchester council (again) to be reused.

The current proposal includes the Isle of Wight, which I don’t think is a good idea. The city region proposal focuses purely on Ryde, a single town on a sparse island. The resources required to improve connectivity between the island and the Portsmouth region should be a lower priority when there are more pressing issues in the city-region, such as addressing housing and transport between Gosport and Portsmouth.

The proposed Portsmouth City Region. Image: author provided.

I realise that many in Hampshire do not like change: it’s difficult for a traditionally rural county to embrace its metropolitan potential. However, city mayors lead to greater productivity by improving the distribution of resources. The establishment of metro mayors for these cities will tackle issues that have been affecting Hampshire for quite some time: the poor transport and the inequality between different communities.