Rocket Soot in the Stratosphere: The Unregulated Climate Threat from Spaceflight's Boom

The stratosphere, a calm layer of Earth’s atmosphere that holds our protective ozone, is becoming a dumping ground for an industry in overdrive: spaceflight. New research, detailed in the journal Atmospheric Chemistry and Physics, reveals that the soot from rocket launches is a potent, lingering agent of atmospheric change, with consequences scientists are only beginning to map.

The issue is one of location and longevity. Unlike airplane exhaust, which is released lower down and washed out by weather, rocket emissions are injected directly into the stratosphere, 20 to 50 kilometers up. There, with no rain to cleanse it, soot from kerosene-burning engines like SpaceX’s Falcon 9 can hover for years. According to the study, each particle of this high-altitude black carbon absorbs sunlight with a warming effect roughly 500 times more powerful than soot at ground level. This can alter stratospheric circulation and ozone chemistry.

This comes as launch rates skyrocket. In 2025 alone, SpaceX conducted over 130 orbital launches, with ambitions for hundreds more annually using its massive Starship. Combined with global efforts from China, Blue Origin, and others, the industry’s growth is steep. Each flight deposits not just soot, but also alumina particles from solid rocket boosters, which can provide a surface for ozone-destroying chemical reactions.

The timing is awkward. The ozone layer, healing since the Montreal Protocol phased out CFCs, now faces a novel threat just as it nears recovery. Researchers stress current damage isn’t catastrophic, but the trajectory is concerning. The regulatory landscape is barren; no national or international body governs stratospheric rocket emissions. The FAA’s reviews focus on ground impacts, and the Montreal Protocol doesn’t cover this modern source.

While some point to methane-fueled rockets like Starship as a cleaner alternative—they produce less soot—their sheer scale and the water vapor they release pose unanswered questions. The industry often highlights the benefits of satellites for climate science and communications, but that doesn’t negate the need to understand the atmospheric cost. With particles from today’s launches destined to linger for years, scientists argue for proactive monitoring and policy, hoping to avoid a future crisis in the thin, cold air far above us.