Wildfire smoke that climbs thousands of meters into the atmosphere could be quietly reshaping our climate in ways we’re just beginning to understand. These fires don’t merely scorch forests; some burn with such intensity that they generate their own weather, including pyrocumulonimbus storms that loft smoke up to about 10 miles (16 kilometers) high. For a long time, scientists suspected that high-altitude smoke lingered for weeks or months, but linking it to climate effects has been extremely challenging due to the difficulty of collecting samples. A breakthrough has changed that.
Researchers from Harvard’s John A. Paulson School of Engineering and Applied Sciences report the first direct measurements of wildfire smoke aged five days in the upper troposphere, roughly nine miles (14.5 kilometers) above Earth. They found unusually large smoke particles that current climate models do not account for, and these particles seem to cool the atmosphere rather than warm it.
Within the smoke plume, the team detected aerosols about 500 nanometers in width—roughly twice the size of typical wildfire aerosols observed at lower altitudes. The researchers propose that this enlargement results from efficient coagulation, where particles merge together.
“Particles can coagulate anywhere in the atmosphere,” said Yaowei Li, the study’s lead author. “But in that particular region, air mixing is unusually slow. That allows wildfire smoke particles to stay concentrated and collide more often, making coagulation much more efficient.”
These larger aerosols influence how much solar radiation reaches Earth’s surface, either by absorbing sunlight or by reflecting it back to space. In this study, the bigger particles caused an increase in outgoing radiation by about 30% to 36% compared with lower-altitude particles, producing a detectable cooling effect that current climate models miss.
More research is needed to understand the full range of impacts that high-altitude wildfire smoke could have on weather and climate. Co-author and project scientist John Dykema notes that the large coagulated particles might affect atmospheric circulation through localized heating, potentially nudging jet streams. “All of these possibilities exist, and we don’t yet have enough data to say which way they’ll go,” he commented.
This finding opens new questions about the behavior of smoke at great heights and its broader climatic consequences. It also suggests that models of past and future climate may need to incorporate these high-altitude aerosols to paint a more complete picture.
The study was published on December 10 in Science Advances. If you’re curious about space science, you can explore more updates on rocket launches, skywatching events, and related topics. For commentary or tips about space news, you can reach Space.com’s community team.
Author Spotlight: Stefanie Waldek is a space writer with a passion for spaceflight and astronomy. Her work spans space tourism, Earth-based astrotourism, and aviation culture, drawing on her background in design and journalism. Learn more about her work at stefaniewaldek.com.
