In 2024 and 2025, atmospheric scientists uncovered a significant "missing piece" in climate modeling: wildfire smoke that reaches the edge of space behaves differently than smoke near the ground.
Traditionally, climate models have focused on the warming effects of soot. However, new research from Harvard’s SEAS and NOAA shows that when smoke is lofted miles high, it undergoes a physical transformation that can trigger a massive, unexpected cooling effect.
1. The "Chimney" Effect: Pyrocumulonimbus Clouds
Most wildfire smoke stays in the lower atmosphere, where it is washed out by rain within days. But intense "megafires" create their own weather systems called Pyrocumulonimbus (pyroCb) clouds.
The Mechanism: These are essentially fire-driven thunderstorms. The intense heat of the fire acts like a giant chimney, catapulting smoke up to 10 miles (16 kilometers) high, straight into the upper troposphere and lower stratosphere (UTLS).
The Altitude: At this height, the smoke is above the "weather layer" (where rain happens), meaning it can stay suspended for months rather than days.
2. The Discovery: Particle "Coagulation"
In a study published in Science Advances (December 2025), researchers used high-altitude NASA aircraft to sample smoke just five days after a New Mexico wildfire. They found something current climate models didn't account for: giant particles.
How it works:
Slow Mixing: In the high-altitude atmosphere, air is very "stratified" and moves slowly.
The Collision: Because the air is still, smoke particles remain highly concentrated. They collide and stick together—a process called coagulation.
Result: The particles grow to roughly 500 nanometers wide—about twice the size of typical wildfire smoke particles found at lower altitudes.
3. The Unexpected Climate Impact: 36% More Cooling
These larger, coagulated particles change the "Earth’s Energy Budget"—the balance of how much solar energy stays on Earth versus how much is reflected back into space.
| Particle Type | Behavior | Climate Effect |
| Standard Smoke | Absorbs sunlight (warming); scatters some light. | Net Warming/Variable |
| Lofted "Giant" Particles | Reflects sunlight much more efficiently. | Significant Cooling |
The Result: Researchers found these large high-altitude particles increase outgoing radiation by 30% to 36% compared to smaller particles. This creates a dramatic regional cooling effect that is currently not included in any major climate models.
4. Risks to the Ozone Layer
While the cooling effect might sound like good news in a warming world, the presence of this smoke at high altitudes has a dangerous side effect: Ozone depletion.
When smoke enters the stratosphere, it introduces organic matter and "brown carbon" into a region that is usually pristine. These particles provide a surface for chemical reactions that break down the ozone layer—the shield that protects Earth from harmful UV radiation. Research from the 2019/2020 Australian "Black Summer" fires showed that smoke-induced chemistry could delay the recovery of the ozone hole by years.
Why This Matters for the Future
As climate change makes wildfires more frequent and intense, we are likely to see more "pyroCb" events. If our climate models don't account for this high-altitude smoke:
Temperature Predictions may be slightly off, as they miss this temporary cooling "brake."
Weather Patterns could shift; the local heating of the stratosphere by these smoke clouds can actually nudge the jet stream, potentially changing where storms travel.
Key Takeaway: Wildfires aren't just local disasters; they are atmospheric "engineers" that can temporarily change the color of our sky and the temperature of our planet from ten miles up.