Regional differences
The researchers note that aerosols can also contribute to cloud formation, which also causes more losses. But the extent of that contribution is much harder to estimate, so the researchers focus on aerosols for much of the analysis. Some of these aerosols are produced naturally, usually from dust raised by winds in desert regions. However, despite deserts’ reputation as sunny paradises, the world as a whole hasn’t built much desert solar infrastructure yet, so this isn’t as important a factor as you might expect.
Coal appears to be a major contributor. Sulfur dioxide aerosols, produced primarily by burning coal, are estimated to account for almost half of the aerosols analyzed here. Carbon-rich material, which typically also comes from fossil fuels, accounts for another 18 percent.
However, the impact of aerosols is not evenly distributed. In China, researchers estimated that aerosols were reducing solar output by 7.7 percent overall and offsetting between a third and half of its annual growth. The researchers note that “the spatial distribution of PV losses in China mirrors that of its coal-fired power capacity,” and an analysis of China’s pollution data shows that 30 percent of losses due to aerosols can be attributed to coal burning.
In contrast, most solar production in the US takes place in the South and West, while coal plants are more common in the East and Northeast. As a result, annual losses in the United States were less than half those seen in China (3 percent).
The good news is that things are improving in China. In response to some serious pollution problems, the country built a new generation of high-efficiency coal plants and retired some of the worst polluters. And the data shows that this also benefits solar energy, as the impact of aerosols has decreased in recent years.
Even with the improvements, it is striking that coal appears to be the only energy source that actively reduces the productivity of what is emerging as its main competitor. It should also provide an impetus to move away from coal more quickly, as at least some of the loss of coal production will be offset by increased productivity from solar power.
Sustainability of Nature, 2026. DOI: 10.1038/s41893-026-01836-5
