A new study published in Science, a scientific journal, on 7 September suggests installing massive wind and solar installations in the Sahara Desert could increase local rainfall, particularly in the neighbouring Sahel region, leading to more vegetation coverage (1). This would create positive feedback that would further increase rainfall ― possibly doubling the rainfall in the region and increasing vegetation coverage by approximately 20 per cent.
Wind and solar power have become important renewable energy sources because they are widely available and offer a viable option for meeting the total global energy demands while mitigating climate change. However, according to the paper, “to substitute for the fossil fuels that currently still dominate worldwide electricity generation, as well as transportation, heating, and industrial energy demands, more large-scale wind and solar farms, would need to be installed throughout the world.”
Large-scale wind and solar farms can have significant effects on land properties and previous models have shown that wind and solar farms produce significant climate change. But the latest model is one of the first to consider how vegetation responds to changes in heat and precipitation as a result of large-scale wind and solar installations.
To study the impact of large-scale wind and solar projects, the modelling study, led by Yan Li from the University of Illinois, considered the effects of placing wind turbines across the Sahara ― an arid region covering more than 9.2 million square kilometers ― around one kilometer apart, and covering 20 percent of the desert with solar panels in different configurations
The Sahara, which used to be lush and green 10,000 years ago but has dramatically changed owing to human influence (2), was chosen because Africa is close to Europe and the Middle East, all of which have large and growing energy demands. Moreover, it is the largest desert in the world, sparsely population, and as it is extremely sensitive to land changes, is an excellent landscape for studying climate change.
It is estimated that the hypothetical solar farm would produce an average of 79 terawatts of power and the wind farm would produce around 3 terawatts. This would be enough to meet global energy demands more than four times over ― around 18 terawatts of power was used last year ― without producing greenhouse gases. But how would these immense installations change the land and climate in the regions?
The computer model showed that wind farms would cause regional warming of the near-surface air temperature and precipitation would increase by as much as 0.25 millimetres per day on average in regions with installations. According to the authors, “the greater nighttime warming takes place because wind turbines can enhance the vertical mixing and bring down warmer air from above.” Solar farms had a similar positive effect on temperature and precipitation but unlike wind farms, were not affected by wind speed.
According to the authors, the findings “indicate that renewable energy can have multiple benefits for climate and sustainable development and thus could be widely adopted as a primary solution to the challenges of global energy, climate change, and environmental and societal sustainability.”
(1) Li, Y. et al. Climate model shows large-scale wind and solar farms in the Sahara increase rain and vegetation. Science (2018). DOI: 10.1126/science.aar5629
(2) Wright, D.K. Humans as Agents in the Termination of the African Humid Period. Frontiers in Earth Science (2018). DOI: 10.3389/feart.2017.00004