Researchers measure overlooked stratospheric aerosols

Complex chemistry that affects the climate occurs every day, high above our heads in the stratosphere. For decades, researchers have sought to model such processes to understand how they might be changing. Now researchers have shown that tiny aerosol particles could play an outsized—and previously overlooked—role in stratospheric chemistry (Science 2026, DOI: 10.1126/science.adw8939).

The research was part of a broader initiative from the National Oceanic and Atmospheric Administration (NOAA) to better understand Earth’s radiation budget. The accounting concept is similar to an expense budget. But instead of calculating cash flow, scientists measure energy: the incoming radiation from the sun, and the outgoing energy from Earth. By understanding the budget, researchers can understand climate trends.

Stratospheric particles floating 10–50 km above the surface play an important role in Earth’s radiation budget. “How they evolve as they age in the stratosphere is very important for the climate, but we don’t know it very well,” says Ming Lyu, a research scientist at the University of Colorado Boulder working in the NOAA Chemical Sciences Laboratory.

This dearth of information is largely caused by a lack of instrumentation, Lyu says. “Usually, we get information about the stratosphere from either satellites or balloon sensors,” she explains. But both have a blind spot: small particles, under 150 nm in diameter.

Satellites measure atmospheric particles by detecting the light they scatter. But ultrafine particles scatter so little light, that they are indistinguishable from background atmosphere. Balloons, on the other hand, carry instruments to sample air directly. Unfortunately, the instruments needed to detect particles smaller than 150 nm are generally too large and heavy for balloons to lift into the stratosphere.

In 2023, during the Stratospheric Aerosol processes, Budget and Radiative Effects (SABRE) campaign, Lyu and her colleagues equipped a high-altitude research airplane with a suite of instruments designed to measure the properties of atmospheric particles. One instrument was entirely custom, built by Lyu and others to measure the tiny aerosols invisible to satellites and balloon-borne sensors. The goal was to provide baseline observations of the size and composition of aerosols in the lower stratosphere.

“We knew that there are small particles in the stratosphere by the basic science, but this is the first time we actually measured the details of these particles in the stratosphere,” Lyu says.

The data were clear: small particles dominated the area the airplane flew through. The scientists did not directly measure the composition of individual nanoparticles, but the data from larger aerosols “strongly suggest that the smaller particles are rich in organics,” Lyu says.

The tiny, organic-rich particles provide the majority of the surface area for chemistry in the lower stratosphere but haven’t been well represented in models of stratospheric chemistry because they’re invisible to most instrumentation.

These findings show that the “stratosphere is a more chemically complex place than we once thought,” Alison Bain, an aerosol researcher at Oregon State University, writes in an email. She was not involved in the work and is interested to see how these new measurements will be incorporated into atmospheric models.

“They’re very important findings,” says Frank Keutsch, a professor of atmospheric science at Harvard University. Keutsch is one of the many scientists participating in SABRE but was not involved in Lyu’s work.

In recent years, Keutsch has seen a renewed interest in studying the stratosphere. Recent flight campaigns are giving scientists an “entirely new picture of the stratosphere,” he says. It will take far more research to fully untangle the chemistry happening in our atmosphere, he adds, but this new work helps fill in some of the blanks.