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The most vibrant sunsets, cloud-choked skies, and cough-inducing days all have something in common: They happen because of aerosols, tiny particles that float in the air. Aerosols can be tiny droplets, dust particles, bits of fine black carbon, and other things, and as they float through the atmosphere they change the whole energy balance of the planet.
Aerosols have an outsized effect on the planet’s climate. Some of them, like black and brown carbon, warm the Earth’s atmosphere, while others, like sulfate droplets, cool it. Scientists think that on balance, the whole budget of aerosols ends up cooling the planet slightly. But exactly how much, and how much that effect can shift over days, years, or centuries is still not totally clear.
The term aerosol is a catch-all for many kinds of little bits of stuff that end up suspended in the atmosphere, from the surface of the planet all the way to the edges of space. They can be solid or liquid, infinitesimally small or big enough to see with the naked eye.
“Primary” aerosols, like...
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