Dust is no longer being swept aside from the most crucial climate conversations — a good thing, because the silty stuff directly affects weather, climate change and human health.
While most of us regard dust as an annoyance, it’s one of the most abundant sources of particles in our atmosphere and has a huge impact on our planet — various types of dust cool and heat Earth, support the ocean’s food chain, maintain carbon sinks in remote waters, and influence the severity of large-scale weather events such as tornadoes, cyclones and monsoons.
And this week’s brutal European heat wave? Yep, dust played a part, said Thomas Painter, a senior research scientist at the University of California, Los Angeles, who specializes in snow hydrology and the impacts of dust emission on ice melt. Climbers in France have stopped scaling Mont Blanc amid fears of melt-induced disasters, such as the deadly ice avalanche on Italy’s Marmolada mountain earlier this month, where the dust cycle set a precedent for large-scale melting and rising temperatures.
“There has been a large amount of dust deposited from the Sahara into the Alps this year, and that has set the stage for warming of the snowpack,” Painter said.
Here are four reasons to care about dust — plus, the new space mission that scientists are counting on to make its study more precise.
It’s everywhere and affects everyone
Mineral dust is one of the atmosphere’s most abundant aerosols — very small particles suspended in the atmosphere.
It derives from the Earth’s crust, and each particle is about twice as thin as the thinnest human hair: 10 micrometers. Strong winds lift and shift more than 1 billion tons of the stuff per year, gusts originating most often from large deserts and depositing the world over.
Painter cautions too narrow a view on this “naturally occurring” classification — humans are not off the hook, he said, from unsettling the dust that impacts our atmosphere today.
Our planet’s temperature depends heavily on dust
When mineral dust swirls up into the atmosphere, its color relative to the color of Earth’s surface helps determine whether it helps cool or heat the planet.
Mineral dust that is darker than Earth’s surface will absorb solar radiation, warming the atmosphere and raising surface temperatures — similar to how wearing a dark shirt in the summer will raise your body temperature. Lighter mineral dust will scatter solar radiation in random directions, diverting heat from Earth’s surface, keeping it cooler.
Dust also plays an important role in the amount of rain different areas of Earth receive, said Paul Ginoux, a senior physical scientist at NOAA’s Geophysical Fluid Dynamics Laboratory.
Surface cooling due to lighter-colored mineral dust can disrupt the water cycle, Ginoux said. Lower temperatures lead to less evaporation, which means less rain in that area, leading to the possibility of drought. Conversely, in his research of dust and the formations of tropical cyclones in West Africa, he found that the warming effects of darker-colored dust can contribute to more rainfall from the storms.
Qinjian Jin, an atmospheric sciences researcher at the University of Kansas, found similar results when studying dust’s effects on monsoons in South Asia. As temperature increases due to atmospheric aerosols, so does pressure. “This results in a stronger monsoon circulation from the Indian Ocean,” he said. “They transport more water from ocean to land, resulting in more precipitation.”
When dust any color darker than white deposits over snowy or icy regions, it absorbs solar radiation and contributes to surface warming — what is known as the albedo effect. That accelerates melting of snow and ice. In the Arctic, it can encourage the growth of algae, toxic to both humans and fish. In Greenland, for example, phosphorus contained in dust may be encouraging the growth of algae on the country’s massive ice sheet — and helping to accelerate its contribution to sea level rise. In the Sierra Nevada, Colorado Rockies and India’s Tibetan Plateau, Ginoux said, “you can have rivers begin to flow earlier [in the year].”
This disrupts the hunting and fishing cycles of Indigenous tribes who depend on reliable seasons and river flows and breakups, as well as communities across the world who depend on glacial melt for potable water, including in Asia’s Third Pole, vast stretches of South America and the U.S. West.
There’s a seriously damaging cycle going on with farming practices and climate change
Before the early 1800s, many societies “tended to stay along coasts and rivers, and did not inhabit interior spaces,” Painter said. But as technological advances during the Industrial Revolution made inland migrations feasible, larger numbers of people and grazing animals began to populate landlocked plains.
In the United States’ Four Corners region, Painter said, settlers — and their sheep and cows — gradually loosened the soil, turning Utah’s once-grassy landscapes into “the stark desert landscapes that they are now” throughout the latter half of the 19th century.
“The dust emission and dust deposition into the Rocky Mountains is at present about five times what it was before 1850,” Painter said.
Poor farming practices, like those that contributed in part to the Dust Bowl of the 1930s, continue to be “major sources of dust worldwide,” Ginoux said. An increasing amount of mineral dust, he said, is entering the atmosphere from arid stretches in Australia, Patagonia, and the United States’ High Plains and Oklahoma panhandle.
But farmers around the world are also being left out to dry by prolonged droughts due to climate change. Withering vegetation is a perfect fuel for wildfires, Ginoux said. His and others’ research have found that disturbed, post-fire soil is also a major source of the world’s mineral aerosols — contributing to a climate feedback loop, literally, of dust to dust.
Last December, a dust storm swept through Kansas, close to home for Jin. The circulation of these dust particles in the atmosphere exacerbated the region’s extreme heat, which destabilizes the atmosphere and can make storm events more likely.
“That’s an example of how heat waves can generate strong circulation, which pick up dust particles from the land,” Jin said. “If we have more heat waves over semiarid regions such as western Kansas, we may expect more mineral dust storms.”
“If dust is causing drought, we will have more dust in the atmosphere,” Ginoux said. It’s what’s called “positive feedback,” said Ginoux. That’s not very positive.
There’s a better way to study dust now, and that may help scientists predict climate change
For years, scientists have used computer simulations to study dust. But these models are based on a limited number of real-life dust samples and run under the assumption that all dust is one uniform color, Ginoux said.
This overgeneralization has prevented researchers from being able to specify dust’s true impacts on weather and pinpoint the geographies it influences.
Now, a new satellite is set to overcome these limitations. Launched by NASA via a SpaceX spacecraft last week, the Earth Surface Mineral Dust Source Investigation (EMIT) will spend the next year attached to the International Space Station in Earth’s orbit, doing just that. It’s not the first mission to collect samples of this kind, but it is the first of such a large scale.
“With EMIT, we’re going to measure the air and land regions and collect 1 billion [samples],” said Robert Green, the principal investigator of the EMIT mission.
This more representative sampling will hopefully validate past research, said Green, and reveal potentially new sources of dust on Earth’s surface. All of that will help scientists better understand the immediate and long-term effects dust has on Earth’s climate.
“There are so many different connections between the dust cycle and the Earth system,” Green said. “It’s atmospheric chemistry; it’s the oceans, it’s terrestrial ecosystems, it’s snow, and it’s humans directly. By understanding it, we might be able to make decisions to mitigate some of the negative impacts and also know how it may change in the future.”
“This is a big deal for understanding the Earth’s aerosol system,” Painter said. “When you see how damn much dust gets blown around, I’m still blown away.”
Thanks to Lillian Barkley for copy editing this article.