Black carbon released by a rocket at high altitude lingers there for 2.5 to 3 years. Eloise Marais, a professor of atmospheric chemistry and air quality at University College London, says that gives it about 540 times the climate effect of black carbon from ships, cars and power plants.
Marais leads a team studying air pollution from satellite launches and re-entries, and she described the findings to Space.com. Her warning is blunt. “The space industry pollution is like a small-scale, unregulated geoengineering experiment that could have many unintended and serious environmental consequences,” she said.
Where the pollution comes from
Most megaconstellation launches today burn kerosene, Marais said, because they usually fly on Falcon 9 rockets, and kerosene produces black carbon. Re-entries add a different problem. Burning satellites generate aluminum oxides, which can damage the ozone layer.
Megaconstellations make both worse. Their satellites have limited lifespans and get replaced about every five years, so launches and deorbits come far more often than they did with older missions built for longer service.
The team calculates likely pollution from expected launches and re-entries in a given period, then feeds the numbers into climate models. “The model can very nicely tell us how much ozone is going to be destroyed from this pollution and how much the climate is going to be altered from this pollution,” Marais said.
What the study found
The latest study, published on Thursday, May 13, in the journal Earth’s Future, found that by 2029 launches for constellations such as Starlink, Amazon Leo and the Chinese projects Guowang and Qianfan will account for more than 40 percent of all pollution from the space sector. Studies show concentrations of potentially dangerous high-altitude pollution from launches and re-entries have risen significantly since the megaconstellation era began in 2020.
On estimates the researchers call conservative, the global space sector will have released more climate-altering chemicals by 2030 than the entire United Kingdom. Marais said the modelling is cautious because actual satellite numbers have consistently outrun what the team expected.
The European Space Agency counts over 15,000 operational satellites, three times as many as in 2020. Starlink accounts for most of the increase, with more than 10,000. Amazon Leo, Guowang and Qianfan are building their own fleets, and some 100,000 satellites may be in orbit by 2030.
A margin that is not yet large
The picture is not one of imminent climate change. Marais said the concentrations of pollutants from launches and re-entries in 2029 will be only about one hundredth of the quantity needed for geoengineering interventions. The worry is accumulation: the more satellites go up, the more particles build up in the upper atmosphere.
Geoengineering refers to possible interventions to reverse global warming, such as Stratospheric Aerosol Injection, which would release light-reflecting particles into the stratosphere. Scientists studying it warn that the effects may be unpredictable, including changes in rain patterns, droughts and unforeseen weather.
“We need to be taking it far more seriously in terms of regulating the pollution that’s coming from launches and reentries,” Marais said. “There also needs to be far more funding funneled into research to study this because we can’t keep up with the space industry.”
