Satellites are creating a massive pollution problem, according to University College London researchers, who say the growing atmospheric carbon source has a 500 times greater climate impact than ground-based emissions, potentially blocking the Sun.

In a recent paper published in the journal Earth’s Future, researchers demonstrate that satellites are driving a significant rise in upper-atmosphere pollution, raising concerns related to the ongoing climate crisis. By the end of this decade, almost half of this pollution will come from satellite megaconstellations launched since 2019, the researchers claim.

Satellite Pollution

While satellites do emit some exhaust when they engage their thrusters, this is not the primary source of pollution they produce, according to the University College London researchers.

Instead, they point to rocket launches, as they generate a massive amount of carbon soot when discarded rocket bodies and dead satellites burn up on reentry into the Earth’s atmosphere. This carbon is particularly problematic, remaining in the upper atmosphere for an extended period and generating a 500-fold climate impact compared to ground emissions.

The team also investigated other forms of launch-related pollution, noting that chlorine released into the atmosphere by these launches harms the ozone layer, which blocks harmful UV rays; however, this impact is far less severe than the carbon soot. Even projecting out to 2029, the team seems confident that rocket launches, accounting for under a tenth of ozone depletion, and some organizations, such as Blue Origin, will be conducting launches that release no chlorine at all.

This is nonetheless important to monitor, they argue, as China’s space launches typically do release chlorine and are expected to grow in the coming years.

Satellite Reentry Carbon

Data for the research were sourced from satellite deployments and rock launches conducted between 2020 and 2022, which found that circulation patterns in the upper atmosphere move very slowly, allowing soot particles to linger for extended periods. In the lower atmosphere, rain and other weather systems remove such particles from car and factory exhaust much more rapidly. With this longer atmospheric life span, each particle in the upper atmosphere has a much greater impact on the environment.

Air pollution from launches and reentry is accumulating in the atmosphere at such a rate that by the end of the decade, it could block as much sunlight as artificial geoengineering projects aimed at reducing global warming. However, the actual cooling effect produced would likely be far below the expected temperature rise due to global warming over the same period, the study authors say.

“The space industry pollution is like a small-scale, unregulated geoengineering experiment that could have many unintended and serious environmental consequences,” said Professor Eloise Marais, the project’s leader and a researcher at UCL Geography. “Currently, the impact on the atmosphere is small, so we still have the chance to act early before it becomes a more serious issue that is harder to reverse or repair. So far, there has been limited effort to effectively regulate this type of pollution.”

The Pace Quickens

Their data indicates that megaconstellations, which the team sees as a significant concern, accounted for 35% of the climate impact of these events, and they expect this to grow to 42% by the end of the decade.

Recent years have seen exponential growth in satellites in near-Earth orbit, primarily driven by the rise of megaconstellations composed of hundreds of thousands of objects. The most well-known of these, SpaceX’s Starlink, accounts for 12,000 individual satellites. Megaconstellations are now consuming over half of the rocket fuel expended, as launches rose from just 114 a year in 2020 to 329 in 2025.

The researchers note that real-world megaconstellation launches between 2023 and 2025 have outpaced their projections based on 2020 to 2022 data, suggesting their predictions may actually underestimate the scale of the problem.

“The cooling effect from the reduction in sunlight that we calculate with our models may sound like a welcome change against the backdrop of global warming, but we need to be extremely cautious,” Professor Marais warned.

“Rocket launches are a unique source of pollution, injecting harmful chemicals directly into the upper layers of the atmosphere and contaminating Earth’s last remaining relatively pristine environment,” lead author Dr. Connor Barker, also with UCL Geography, noted.

“Though this soot’s impact on climate is currently much smaller than other industrial sources, its potency means we need to act before it causes irreparable harm,” Barker says.

The paper, “Radiative Forcing and Ozone Depletion of a Decade of Satellite Megaconstellation Missions,” appeared in Earth’s Future on May 14, 2026.

Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.

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