Transition to solar could change the earth

We won't have a choice for energy for much longer. In the near future, we are all going to have to make the switch to renewable energy – if not out of concern about climate change then simply because fossil fuels will soon run out. But even sustainable energy technologies may have a slight effect on global climate, according to a study published yesterday in Nature Climate Change. In the study, researchers used computerized climate models to study what would happen if the world’s entire energy supply were converted to solar. They assumed that solar panels would be installed in the major desert regions of the world, where the supply of sunlight is greatest, and in urban areas, where the demand for power is highest.

Solar absorption

In regions covered by solar panels, less solar radiation gets absorbed by the earth, because it gets absorbed by the solar panels (and converted to electricity) instead. Widespread establishment of solar panels would decrease absorption of solar radiation by up to 19% in desert areas, the researchers found. This, in turn, has cascading effects on the climate. On a global scale, the changes from solar panel installation are small compared to those projected to occur due to greenhouse gases. But at a regional level, some of these climatic alterations could be significant, the researchers say. The average temperature in desert regions would shrink by about two degrees Celsius. Desert precipitation could also decrease by over 20%, mostly because the presence of solar panels also reduces cloud cover.

Desert cooling would change the jet stream

According to the researchers’ model, this desert cooling would lead to alterations in wind patterns, a shift in the location of the jet stream, and altered precipitation levels for many regions. Much of Asia, sections of the Middle East, Australia, and the tropical Pacific would lose up to 25 centimeters of average annual precipitation. Instead, that precipitation would shift to Europe, the North Pacific, western North America, tropical Africa, and the southeast Indian Ocean. (These weather patterns are opposite to those predicted to arise from greenhouse gas-caused warming.)

Regions to the East, or downwind, of desert regions covered by solar panels would also cool off by about one degree Celsius. (Exceptions are India and the West Coast of North America, which, due to lower precipitation and altered wind patterns respectively, warm by about one degree Celsius instead.)The study presents an extreme scenario: the researchers pretended that 100 percent of the land area in cities and deserts would be covered with solar panels, which isn’t realistic. Those solar panels would produce almost 800 terawatts of power, much more than the world is likely to need. But the researchers say this sort of exercise can unveil mechanisms underlying the climate system and help interpret the results of more realistic modeling exercises. So they also created a version of their model that more accurately reflects likely future demands for power. In this scenario, solar panels would be installed across urban areas globally and in a portion of the Egyptian desert, covering about ten percent of the total land area devoted to solar panels in the first version of the model.

Surface temperatures

Here the patterns of surface temperature change are comparable in broad strokes to those seen in the extreme version of the model, but much more modest. For instance, global temperatures would decline by about 0.04 degrees Celsius, the researchers found. This smaller global solar grid would produce about 59 terawatts of power per year. That’s still plenty sufficient to cover global demand for electricity, which the Intergovernmental Panel on Climate Change has estimated to be, at most, 45 terawatts per year by 2100.

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