Albuquerque Journal

Study reveals unsung climate cooler: Atmospheri­c dust

It works as global warming antidote

- BY COCO LIU

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.

Global temperatur­es are currently around 2.2 degrees higher than 1850 levels, and heading toward 2.7 degrees of warming, which scientists consider catastroph­ic. But that 2.2-degree increase would be roughly 0.1 degrees higher were it not for an increase in global atmospheri­c dust, according to a peer-reviewed study published last 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. “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.”

 ?? QILAI SHEN/BLOOMBERG ?? A person walks on a footbridge with buildings shrouded in haze in the background in Beijing in 2017.
QILAI SHEN/BLOOMBERG A person walks on a footbridge with buildings shrouded in haze in the background in Beijing in 2017.

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