Dust rising from desert storms and arid landscapes has helped cool the planet over the past few decades, and its presence in the atmosphere may have obscured the true extent of global warming caused by fossil fuel emissions.
Atmospheric dust has increased by 55% since the mid-19th century, one analysis suggests. And that increased dust may have hidden up to 8% of the warming from carbon emissions.
Analysis by atmospheric scientists and climate researchers in the US and Europe attempts to account for the varied and complex ways in which dust has affected global weather patterns and concludes that, overall, it has worked to somewhat offset the warming effects of greenhouse gases. The study, published in Nature Reviews Earth and Environment, warns that current climate models do not take into account the effect of atmospheric dust.
“We’ve been predicting for a long time that we’re heading to a bad place when it comes to greenhouse warming,” said Jasper Kok, an atmospheric physicist at UCLA who led the research. “What this investigation shows is that, until now, we have had the emergency brake activated.”
About 26 million tons of dust are suspended in our atmosphere, scientists estimate. Its effects are complicated.
Dust, along with synthetic particle pollution, can cool the planet in a number of ways. These mineral particles can reflect sunlight away from Earth and dissipate cirrus clouds high in the atmosphere that warm the planet. Dust that falls into the ocean encourages the growth of phytoplankton, microscopic plants in the ocean, which absorb carbon dioxide and produce oxygen.
Dust can also have a warming effect in some cases, darkening snow and ice and encouraging them to absorb more heat.
But after counting everything, it seemed clear to the researchers that the dust had a general cooling effect.
“There are all these different factors that influence the role of mineral dust in our atmosphere,” said Gisela Winckler, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. “This is the first review of its kind that really brings all these different aspects together.”
Although climate models have so far been able to predict global warming fairly accurately, Winckler said the review made it clear that these predictions haven’t been able to pin down the role of dust especially well.
Limited records from ice cores, marine sediment records, and other sources suggest that dust in general has also been increasing since pre-industrial times, in part due to development, agriculture, and other human impacts on landscapes. But the amount of dust also appears to have decreased since the 1980s.
More data and research are needed to better understand these dust patterns, Winckler said, and to better predict how they will change in the coming years.
But if the dust in the atmosphere decreases, the warming effects of greenhouse gases could accelerate.
“We could start to experience faster and faster warming because of this,” Kok said. “And maybe we’re realizing that reality too late.”
