Dust from desert storms and arid landscapes has helped cool the planet over the past decades, and its presence in the atmosphere may have obscured the true extent of global warming caused by fossil fuel emissions.
Analysis shows that atmospheric dust has increased by about 55% since the mid-19th century. And this increase in dust may hide up to 8% of global warming in carbon emissions.
The analysis, conducted by atmospheric scientists and climate researchers in the United States and Europe, seeks to explain the diverse and complex ways in which dust has affected global climate patterns, concluding that, overall, dust has offset the warming effect of the gases. greenhouse. . The study, published in Nature Review Earth and Environment, warns that current climate models do not take into account the effect of dust on the atmosphere.
“We have long predicted that we were heading to a bad place in terms of warming,” said Jasper Cook, an atmospheric physicist at UCLA who led the research. “This research shows that, until now, we had emergency brakes.”
Scientists estimate that about 26 million tons of dust are suspended in our atmosphere. The effect is complex.
Dust, combined with man-made particulate pollution, can cool the planet in several ways. These metallic particles can reflect sunlight away from Earth and scatter cirrus clouds high in the atmosphere which 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 causing it to absorb more heat.
But after they wrote it all down, it seemed clear to the researchers that the dust had an overall cooling effect.
“There are all these different factors that contribute to the mineral dust in the atmosphere,” said Gisela Winkler, climate scientist at Columbia University’s Lamont-Doherty Earth Observatory. “This is the first review of its kind that really brings together all of these different aspects.”
Although climate models have so far been able to predict global warming with great accuracy, Winkler said the review shows that those predictions don’t pinpoint the role of dust very well.
Limited records from ice samples, marine sediment records, and other sources suggest that dust in general has also increased since preindustrial times—due in part to development, agriculture, and other human impacts on the landscape. But it also seems that the amount of dust has decreased since the 1980s.
Winkler said more data and research is needed to better understand these dust patterns, and to better predict how they will change in coming years.
But if there is less dust in the atmosphere, the warming effect of greenhouse gases can increase.
“We can start to experience accelerated warming because of this,” Cook said. “Perhaps we will realize this reality too late.”
