As more and more rockets are launched into space, the pollution they emit could have a growing effect on Earth’s atmosphere and weather systems.
Many rockets today use kerosene, which is burned with an oxidiser – liquid oxygen – to produce thrust. This includes SpaceX’s Falcon 9, currently the most frequently launched rocket in the world, responsible for 31 of the 135 successful launches globally in 2021.
A by-product of this process is black carbon, soot-like grains thrown out in the exhaust. While any carbon-based fuel produces black carbon, kerosene is a particularly bad offender, and only rockets deposit black carbon high in the atmosphere. Previous work has shown that , trapping heat from the sun and potentially damaging the ozone layer.
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at the National Oceanic and Atmospheric Administration in Boulder, Colorado, and his colleagues modelled what sort of atmospheric effects we might expect from black carbon emissions if launch rates increase. They examined a scenario where launches increased to 10 times their current level by 2040, in line with current trends, increasing the amount of black carbon deposited in the atmosphere per year from about 1 million kilograms to 10 million kilograms.
They found stratospheric temperatures could increase by up to 1.5°C in such a scenario, while jet wind speeds could decrease by 5 metres per second.
These changes could affect the movement of high-pressure weather systems, particularly in the tropics, where most launches take place. As a result, larger amounts of black carbon are concentrated in these regions and this may slightly change the paths of tropical storms.
There could also be a slight depletion in ozone levels, although perhaps only by a few per cent. “It’s not the end of the world,” says Maloney. “But it’s still something to be aware of.”
at University College London says there are some causes for concern. “The scenario they investigate is plausible,” she says. “The effect on the stratosphere is concerningly high.”
Switching to cleaner fuels could be a solution to the problem. SpaceX is already planning to use methane in its upcoming Starship rocket, rather than kerosene, which Maloney says produces less black carbon.
If launch rates increase to 100 times current levels and steps aren’t taken to address black carbon emissions, however, the effects could be much worse. “In the larger-emission scenarios, that would start messing with things,” says Maloney. “We would want to avoid that future.”
Journal of Geophysical Research: Atmospheres
