You know what would be brutal? If we installed a bunch of solar panels to stop global warming and they caused it instead. But that pesky physics warns that it could happen, in the form of a claim in The Conversation that “Solar panels in Sahara could boost renewable energy but damage the global climate”. We are not making this stuff up. If we could, we’d be making a living writing comedy instead of bugging readers to support the Climate Discussion Nexus. (By clicking here.) See, solar panels are, um, inefficient, and turn about 15% of the energy they absorb into electricity. But they are also efficient, absorbing a walloping load of energy. So the remaining 85% turns into heat with great efficiency and, as always with climate change, causes bad things to happen like plants growing in a desert. Bad? Yes, because according to somebody’s computer it causes a runaway greenhouse effect. Boo. Bad plants.
The article by Zhengyao Lu of Lund University and Benjamin Smith of the Hawkesbury Institute for the Environment at Western Sydney University begins brightly enough by noting that “The world’s most forbidding deserts could be the best places on Earth for harvesting solar power – the most abundant and clean source of energy we have. Deserts are spacious, relatively flat, rich in silicon – the raw material for the semiconductors from which solar cells are made — and never short of sunlight.”
Also, we add, they tend to be largely uninhabited, a non-trivial consideration given the huge footprint of solar. (How big a footprint? Some engineers recently computed that to power Germany with the sun would require covering 7% of the land area of Spain with solar panels, and the necessary battery backup would require 4 times the total annual global battery production. That’s just Germany, and the whole works would have to be replaced every 15 years. To power the EU would require covering 40% of Spain with solar panels and 24 times the total global battery production. Just replacing the batteries that wear out each year would take 3x the annual amount of global silver production.)
Here’s where things get, well a bit dark. “While the black surfaces of solar panels absorb most of the sunlight that reaches them, only a fraction (around 15%) of that incoming energy gets converted to electricity. The rest is returned to the environment as heat. The panels are usually much darker than the ground they cover, so a vast expanse of solar cells will absorb a lot of additional energy and emit it as heat, affecting the climate.”
Vast being the operative word, because “the scale of the installations that would be needed to make a dent in the world’s fossil energy demand would be vast, covering thousands of square kilometres. Heat re-emitted from an area this size will be redistributed by the flow of air in the atmosphere, having regional and even global effects on the climate.” And all bad, naturally. Or rather unnaturally.
The authors note that “A 2018 study used”… what else? “a climate model”. Which “revealed that when the size of the solar farm reaches 20% of the total area of the Sahara, it triggers a feedback loop. Heat emitted by the darker solar panels (compared to the highly reflective desert soil) creates a steep temperature difference between the land and the surrounding oceans that ultimately lowers surface air pressure and causes moist air to rise and condense into raindrops. With more monsoon rainfall, plants grow and the desert reflects less of the sun’s energy, since vegetation absorbs light better than sand and soil. With more plants present, more water is evaporated, creating a more humid environment that causes vegetation to spread.”
Yay! The desert turns green. In the face of such news only pedants would quibble that the model didn’t “reveal” anything, it speculated. And then got unhappy. “So, a giant solar farm could generate ample energy to meet global demand and simultaneously turn one of the most hostile environments on Earth into a habitable oasis. Sounds perfect, right?” Ah but nay.
The model “showed there could be unintended effects in remote parts of the land and ocean that offset any regional benefits over the Sahara itself. Covering 20% of the Sahara with solar farms raises local temperatures in the desert by 1.5°C according to our model. At 50% coverage, the temperature increase is 2.5°C. This warming is eventually spread around the globe by atmosphere and ocean movement, raising the world’s average temperature by 0.16°C for 20% coverage, and 0.39°C for 50% coverage.” And you know the next bit: “the polar regions would warm more than the tropics, increasing sea ice loss in the Arctic. This could further accelerate warming, as melting sea ice exposes dark water which absorbs much more solar energy.” And we are all going to dieeeeeeeeee.
Specifically in this manner: “This massive new heat source in the Sahara reorganises global air and ocean circulation, affecting precipitation patterns around the world. The narrow band of heavy rainfall in the tropics, which accounts for more than 30% of global precipitation and supports the rainforests of the Amazon and Congo Basin, shifts northward in our simulations. For the Amazon region, this causes droughts as less moisture arrives from the ocean. Roughly the same amount of additional rainfall that falls over the Sahara due to the surface-darkening effects of solar panels is lost from the Amazon. The model also predicts more frequent tropical cyclones hitting North American and East Asian coasts.”
Yeah. Because you told it to. At the end they admit that their boast about “the complex feedbacks” was a bit boastful, since “Some important processes are still missing from our model, such as dust blown from large deserts.” But never mind. We knew what we were looking for and gosh we found it right here in the program we wrote ourselves.
Interestingly, they concede also that “This scenario might seem fanciful, but studies suggest that a similar feedback loop kept much of the Sahara green during the African Humid Period, which only ended 5,000 years ago.” So why didn’t that one cause a runaway greenhouse effect? Ah, because it was natural and only man is vile.
Indeed a recent study of warming greening the Sahara duly concluded that this time it would brown it. But only of course if that outcome is bad.
Fortunately there isn’t enough silicon and silver to make all those solar panels so no need to lose sleep over them turning on us with a savage snarl. See, according to NASA the planet continues to “green” ominously, a dreadful process in which among other things the lovely dusty dry planet-cooling Sahara desert is being encroached on by those rotten dark low-albedo plants-of-death things, losing about 8% of its area or 700,000 km2 since about 1980.
Better cut them down and plant solar panels. No, wait…
Forget about mining enough silver to make batteries. The real problem is finding enough child labour to mine all the cobalt we will need for the "green energy" revolution - what with birth rates falling and all.