Satellite megaconstellations pollute upper atmosphere, study warns of unregulated climate impact

A University College London study finds that the rapid expansion of satellite megaconstellations is now a major source of atmospheric pollution. Launches for constellations such as SpaceX’s Starlink, Amazon’s Leo and Chinese systems Guowang and Qianfan contributed about 35% of the space sector’s climate impact in 2020, a share that could rise to 42% by 2029. Researchers estimate the sector may emit roughly 870 tons of soot annually, comparable to the total soot output of all passenger cars in the United Kingdom.

The soot, black carbon from kerosene‑fuelled rockets, remains in the upper atmosphere for years and has a much stronger warming effect than ground‑level emissions. Re‑entries of satellites and rocket bodies also release metal oxides that interact with ozone chemistry. No international regulations currently govern these emissions, prompting calls for global standards and a shift to greener launch fuels. The study warns that, without oversight, the growing waste stream from tens of thousands of satellites could become a routine, untested geo‑engineering experiment.