Dust from desert storms and barren landscapes has helped cool the planet over the past several decades, and its presence in the atmosphere may have obscured the true extent of global warming caused by fossil fuel emissions.
An analysis indicates that atmospheric dust has increased by about 55% since the mid-19th century. And this increased dust may have hidden up to 8% of the global warming in carbon emissions.
The analysis, conducted by atmospheric scientists and climate researchers in the United States and Europe, attempts to account for the diverse and complex ways in which dust has affected global climate patterns, concluding that, overall, it has acted to some extent to counteract 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 influence of atmospheric dust.
“We’ve long predicted that we’re headed for a bad place when it comes to warming warming,” said Jasper Cook, an atmospheric physicist at UCLA who led the research. “What this research shows is that, until now, we’ve had emergency brakes.”
Scientists estimate that about 26 million tons of dust are suspended in our atmosphere. Its effects are complex.
Dust, combined with artificial 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 that are warming the planet. Dust that falls into the ocean encourages the growth of phytoplankton — microscopic plants in the ocean — that absorb carbon dioxide and produce oxygen.
Dust can also have a warming effect in some cases – darkening snow and ice, and causing them to absorb more heat.
But after they wrote everything down, it seemed clear to the researchers that the dust had an overall cooling effect.
“There are all these different factors that play the role of 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 all these different aspects together.”
Although climate models have so far been able to predict global warming with a great deal of accuracy, Winkler said the review showed that those predictions weren’t able to pinpoint the role of dust very well.
Limited records from ice samples, marine sediment records, and other sources indicate that dust in general has also been increasing since preindustrial times—due in part to development, agriculture, and other human impacts on the landscape. But it also appears that the amount of dust has been decreasing since the 1980s.
Winkler said more data and research is needed to better understand these dust patterns, and better predict how they will change in the coming years.
But if dust decreases in the atmosphere, the warming effects of greenhouse gases may accelerate.
“We can start to experience faster and faster warming because of this,” Cook said. “Maybe we will wake up to this reality too late.”
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