Earth is getting less dusty – which is both good and bad

The atmosphere is less dusty than it was

NASA

Levels of dust in the atmosphere have dropped significantly over the past two decades. This is good news for our lungs, but could contribute to increased global warming.

Satellites are the best tool researchers have for continuously monitoring dust across the planet, but it is difficult to separate it out from other aerosol types such as smoke and pollution.

To see the true picture, Ashok Gupta at the University of California, Los Angeles, and his colleagues collated information from four satellites collected between 2003 and 2023, and three atmospheric aerosol databases, before checking the information against ground-based stations. All the sources agreed that it has become less dusty, with the team’s estimates suggesting dust had declined by about 10 per cent globally over this period.

The dust in question travels from the ground up to the upper atmosphere, though most of it accumulates below an altitude of around 6 kilometres. It includes the dust lifted during major storms, along with the dust emitted from deserts day to day.

Preliminary analysis suggests the dust decline is largely due to a fall in surface wind activity. “Dust emission is very sensitive to wind speed, so even a modest weakening of surface winds can noticeably reduce how much dust is lofted into the air,” says Gupta. “Increased vegetation cover – greening – is another likely contributor, particularly over Asia and especially China.”

Dust has a modest net cooling effect on the planet, mainly by reflecting sunlight back into space, so when dust declines, some of that cooling effect is lost. It also affects clouds and rainfall, including monsoon circulations, and carries nutrients such as iron and phosphorus that fertilise the oceans and forests.

“A sustained decline in dust therefore ripples through all of these,” says Gupta. But from a public health perspective, a decline in airborne dust is “good news for hundreds of millions of people living in dust-exposed regions, from the Sahel and the Middle East to northern China”.

Tegan Clark at the Australian National University in Canberra says that better land management practices and the regreening of land that was experiencing desertification may be contributing to the reduction.

“In Australia, sustainable land management practices in western New South Wales have resulted in increased vegetation cover, which is critical for reducing wind erosion,” says Clark. “In China, there has been evidence that the Great Green Wall project has reduced the frequency of dust storms.”