Airborne desert dust may be playing a larger role in shaping weather and climate than previously understood, and findings from UCLA could lead to more accurate forecasts and climate models, according to a study published Tuesday.
Researchers said they found that dust in the atmosphere traps about twice as much heat as earlier estimates suggested, a factor that could significantly refine how scientists model both short-term weather patterns and long-term climate change.
The study determined that dust’s heat-trapping effect is roughly 10% of the warming caused by human-emitted carbon dioxide, compared with previous estimates of about 5%.
Atmospheric dust plays a dual role in the climate system, reflecting sunlight back into space while also absorbing and retaining heat like an insulating blanket. Although dust is still believed to have a slight overall cooling effect, researchers said its warming influence has been underestimated.
“Improving how models represent warming caused by dust could therefore help improve both weather forecasts and climate projections,” Jasper Kok, the study’s lead author and UCLA scientist, said in a statement.
“Regions with more dust will be a little warmer, leading to higher surface temperatures and faster evaporation. This can alter atmospheric motions and shift where and when rainfall occurs — for example, by suppressing precipitation in some regions while enhancing it in others. Such effects are expected to be strongest in regions downwind of major deserts such as in the Sahara, the Middle East and East Asia.”
The study drew on satellite observations, aircraft measurements and climate simulations, along with meteorological data, to develop a global estimate of how dust affects temperature and atmospheric behavior.
“Climate models are slightly too conservative, because they typically omit the ways dust scatters heat emitted by Earth’s surface and atmosphere back downward,” Kok said.
“Our previous research showed that the models also undercount the amount of very coarse dust particles in the atmosphere, which are especially effective at trapping heat. There are about 20 million metric tons of very coarse dust in the sky — the mass of roughly 4 million African elephants — and models account for only about a quarter of that.”
Depending on factors such as particle size, elevation and concentration, dust can either cool the planet by reflecting sunlight or warm it by absorbing and re-emitting heat. Previous research has shown that these competing effects result in a small overall cooling impact, slightly slowing but not stopping global warming, according to the study.
Dust levels increased during the 20th century, peaking in the 1980s, and remain elevated compared with pre-industrial levels, researchers said. Sources include major deserts such as the Sahara and the Gobi, as well as drying lakebeds including the Salton Sea, Owens Valley and the Great Salt Lake.
“Current climate models undercount the heating effect of dust by about half. The climate models remain effective and useful, and this will make them even more precise,” Kok said.
The study was published in Nature Communications.