At the rate things are going, rocket contrails may one day join airplane contrails as chief polluters. Blasting people off to the Moon, to Mars, or just for a brief excursion into the upper atmosphere for a view of this beautiful blue marble is the stuff of science fiction novels come true.
The trouble is, rocket emissions can exacerbate global warming and ozone loss. Over time, they can also slow down jet stream currents, those bands of wind that form the dividing line between weather extremes.
Concerns about rocket emissions are based largely on projections of growth of this industry, rather than current levels of traffic. The rocket industry is expected to grow exponentially in the coming decades, from $424 billion a year or two ago to more than $1 trillion by 2050.
A small number of scientific studies have emerged recently that focus on black carbon and other rocket exhaust contents that in large enough quantities, distributed throughout the stratosphere (12 to 31 miles up), will heat up the planet, change the weather, and impede our progress on restoring the ozone layer.
NASA’s plans to blast human beings and equipment across the solar system are going to require many heavy duty rocket launches. Space tourism and the lofting of “constellations” of tens of thousands of satellites will add to the emissions problem.
Scientists are saying the space industry needs regulation like the Montreal Protocol (1987), which limited use of chlorofluorocarbons and halons, allowing the ozone layer a chance to start its recovery.
Black carbon in the stratosphere has 475 times the power to cause global warming, ounce for ounce, as black carbon emitted by trucks, cars, airplanes, and trains in the troposphere, which is the layer of atmosphere closest to the planet’s surface (Graphic).
There are other compounds in the plumes of rocket exhaust that are concerning, such as nitrous oxides, but it’s the character of rockets as vertical polluters that is more at issue here. What goes into the stratosphere hangs around for a very long time. Further, as spent rocket stages fall back to Earth, and as satellites and other space junk see their orbits decay and plunge to Earth, they, too, leave emissions that spur global warming and ozone loss.
“These findings demonstrate an urgent need to develop environmental regulation to mitigate damage from this rapidly growing industry,” Ryan et al. wrote in their 2022 study published in the peer-reviewed journal Earth’s Future.
