Dust tends to get a bad rap: It’s been known to turn skies orange in Europe, and routinely chokes millions with air pollution. But all that dust has an unexpected positive impact, too: It is helping keep the planet just a little bit cooler.
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Global temperatures are currently around 2.2°F (1.2°C) higher than 1850 levels, and heading toward 2.7°F of warming, which scientists consider catastrophic. But that 2.2° increase would be roughly 0.1°F higher were it not for an increase in global atmospheric dust, according to a peer-reviewed study published this week in Nature Reviews Earth and Environment.
“The increase in dust has likely masked some of the power of greenhouse gases to warm the planet,” says Jasper Kok, co-author of the study and a professor at the University of California, Los Angeles (UCLA). “In the future, when we’re not likely to see similar increases in dust — and might even see a decrease — greenhouse gases might warm the planet even more than climate models already predict.”
To reach their conclusions, Kok and his co-authors started by using satellite and ground measurements to quantify microscopic mineral particles in the air, finding a total of 26 million tons — equivalent to the weight of about 5 million African elephants. They also gathered data from ice cores, marine sediment and peat bogs to understand buildup of atmospheric dust over time. Since the mid-1800s, they found, the amount of dust has increased by as much as 55%.
The researchers then analyzed how atmospheric dust interacts with clouds, oceans, sunlight and land, which play different roles in temperature changes. While dust over deserts that already reflect sunlight can produce warming, for example, atmospheric dust can also scatter sunlight, alter cloud cover and deposit nutrients such as iron and phosphorus into the ocean. Those nutrients help boost the growth of phytoplankton that absorb carbon dioxide. All of these impacts factored into the researchers’ conclusion that atmospheric dust “net cools the climate.”
“This research is important because it attempts to pin down the effects of dust on the energy that enters and leaves the climate system, and how those effects have changed over time,” says Anthony Broccoli, a professor specializing in atmospheric science at Rutgers University, who is not involved in the study. He doesn’t expect the findings to substantially alter future climate projections, but says they do provide “a target for improving how dust is represented in climate models.”
Indeed, the study’s implication is not that atmospheric dust is good, or that countries should reverse course on stopping soil erosion, a major contributor to its proliferation. Increased dust in the air poses a serious threat to human health, and degraded land contributes to food insecurity. The researchers aim instead to shed light on the fact that changes in atmospheric dust are not currently factored into climate modeling.
“We want climate projections to be as accurate as possible,” Kok says, “and this dust increase could have masked up to 8% of the greenhouse warming.”
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