Regional differences
Aerosols can also contribute to cloud formation, causing additional losses, the researchers note. But the extent of this contribution is more difficult to estimate, so the researchers focused on aerosols for most of the analysis. Some of these aerosols are formed naturally, usually from dust blown up by winds in desert regions. However, despite deserts being known as sunny havens, the world as a whole has yet to build much solar infrastructure in the desert, so it’s not as much of a factor as you might expect.
Coal appears to be the main contributor. It is estimated that sulfur dioxide aerosols, mainly from coal combustion, account for about half of the aerosols analyzed here. And carbon-rich material, usually from fossil fuels, makes up another 18 percent.
However, the effect of aerosols is not evenly distributed. Researchers in China estimated that aerosols reduce solar output by a total of 7.7 percent, offsetting one-third to one-half of the annual increase. “The spatial distribution of photovoltaic losses in China reflects its coal-fired power capacity,” the researchers note, and an analysis of pollution data from China shows that 30 percent of losses due to aerosols can be attributed to coal burning.
In contrast, most solar generation in the United States occurs in the South and West, while coal plants are more common in the East and Northeast. As a result, annual losses in the US were less than half of those seen in China (3 percent).
The good news is that things are looking up in China. In response to some serious pollution problems, the country has built a new generation of highly efficient coal plants and retired some of the worst polluters. Data show that it has also benefited from solar energy through the influence of aerosols in the last few years.
Even with improvements, it’s surprising that coal appears to be the only energy source actively reducing the productivity of a product shaping up to be its main competitor. It should also prompt a faster shift away from coal, as at least some of the losses in coal production will be offset by increased productivity from solar power.
Nature Sustainability, 2026. DOI: 10.1038/s41893-026-01836-5
