Currently, the Earth's inhabitants are, on average, consuming about 17.5TeraWatts of power. It's estimated that an aggressive rollout of solar panels could generate at least 400TW, and possibly much, much more. But that would involve paving over a lot of the Earth's surface with solar panels, in many cases covering relatively reflective sand with dark black hardware. Could this have its own effects on the climate?

The answer turns out to be remarkably complex. That's in part because the panels don't simply absorb the energy of the light—a fraction of it gets converted to electricity and shipped elsewhere. A team of US and Chinese scientists decided to account for all of this and found out that massive solar installations would cause changes in the climate, but the changes would be minor compared to what we'd see from continued greenhouse gas emissions.

The authors created a number of scenarios to tease out the influence of the panels, and they used climate models to examine the changes they drove. The first method involved covering most of the Earth's deserts and urban areas with solar panels (this would, of course, lead to a ridiculous overproduction of electricity). In a second, the power harvested by these panels was then sent to urban areas and dissipated as heat. Finally, for a somewhat more realistic view, they simply covered most of the deserts of Egypt with panels.

Future solar harvesting techniques were assumed to have an efficiency of about 30 percent. For a panel-covered area, the authors took the energy from incoming sunlight and subtracted 10 percent, which is assumed to be reflected back to space. Thirty percent of the remainder was converted to electricity, with the remaining 70 percent assumed to be absorbed and converted to heat.

The net result of all of this is that even though more light is absorbed at the site of the panels, less of it is released there as heat. In the authors' model runs, desert regions cooled by nearly 2 degrees Celsius. This actually causes the deserts to dry out further, leading to global shifts in precipitation and wind patterns. Meanwhile, the energy that's being harvest pumps 800TW into the environments around urban areas, raising temperatures by over a degree Celsius. The net result is a slight rise in global temperatures (about 0.6 degrees Celsius), along with the wind and precipitation changes.

Sharp-eyed readers, however, will have noted that humanity as a whole doesn't even use 20TW, much less 800. The authors knew going in that covering all deserts was completely unrealistic, which is why they ran a scenario where panels were only installed in Egypt. This still generates an absurd excess of power, but it's notably less absurd—roughly 60TW. Here, there's a tiny global cooling (0.04 degrees Celsius) and only some local changes in the weather patterns.

So contrary to what you might expect, painting the desert photovoltaic black actually reduces the local heating, provided we have some place to ship the power to. And in every single case—even when we're harvesting 800TW of energy from the Sun—the global changes are small relative to what we should expect from greenhouse warming.

Nature Climate Change, 2015. DOI: 10.1038/NCLIMATE2843 (About DOIs).