See how aerosols fly through Earth’s skies

The sky abounds with tiny bits of solid or liquids known as aerosols. Some are flecks of black carbon or dust. Others are specks of sulfates or sea salt. All play roles in managing Earth’s temperature. And a new NASA visualization reveals how these airborne bits swirl through about. It now shows how aerosols can affect air quality far from their sources.

NASA’s Goddard Earth Observing System created the visual. It combined observations from space and the ground together with computer models. They map where these  aerosols traveled over a six-week span last year.

Sulfates (green, in the visual) are linked most often to the burning of fossil fuels, especially coal. Some countries, such as the United States, have reduced coal burning. Many Asian nations, however, still rely on it for power, releasing lots of sulfates.

Explainer: What are aerosols?

Volcanoes also spew sulfates. If the NASA visual had captured the powerful 1991 eruption of Mount Pinatubo in the Philippines, the global atmosphere would be blanketed in green.

The Sahara Desert is the planet’s largest source of atmospheric dust (purple). Trade winds blow Saharan dust across the Atlantic Ocean. There, it’s thought to fertilize Earth’s largest rainforest — the Amazon. Saharan dust may also reduce hurricane activity in the Atlantic Ocean. How? By slowing moisture flow through the atmosphere.

Black carbon (red) comes largely from burning vegetation. Major sources include those soot-emitting fires purposely set to clear forests and to prepare farmland for future crops. Land managers do this in sub-Saharan Africa and the Amazon. Major wildfires in North America also spew lots of black carbon.

Winds and crashing waves loft sea salt (teal) into the air. Where winds are faster, more salt enters the air. A lot of salt gets lofted over the Southern Ocean. Strong winds there called the Roaring Forties race around the globe with little land to slow them.

This NASA visualization shows the spread of aerosols in the atmosphere from August 1 to September 14, 2024. Major aerosol types include sulfates (green), black carbon (red), dust (purple) and sea salt (teal). 

Tiny bits, big influence

When greenhouse gases get spewed into the air, they can stay in the atmosphere for years, spreading around the world. Aerosols, in contrast, stay aloft for only days to weeks. Often, they form regional plumes drifting through the skies.

Most high-flying aerosols counter climate warming. They do this in part by reflecting the sun’s warming light back into space. Water vapor in the atmosphere also can latch onto aerosols, condensing into a liquid. This increases the number of droplets in clouds. In that way, clouds too can reflect more heat and sunlight into space.

One exception to this climate-cooling effect: black carbon. These aerosols absorb the sun’s energy, warming the air. But overall, aerosols have offset about one third of climate warming, says Sarah Doherty. That would come to about 0.5º Celsius (0.9º Fahrenheit. An atmospheric scientist, Doherty works at the University of Washington in Seattle.

As countries take steps to tackle air pollution, the cooling effect of aerosols is expected to fade. In fact, this may already be underway. “We’ve seen a recent acceleration in the rate of [global] warming,” Doherty says. There are some hints that this is at least partly due to fewer aerosols in the atmosphere.