It is perhaps a bit counterintuitive, given our general perception of the greenhouse effect and the blanket of increasingly warm gases above our heads, but more carbon dioxide in the atmosphere also has an impact on the beginnings of outer space. As NASA has explained:
As layers like the thermosphere cool in that fashion, that makes it contract, making it less dense. And that means the stuff up there will experience less drag, their orbits will decay more slowly, and they will stay up there longer. This is bad.
“[P]erhaps unintuitively, climate change and orbital debris accumulation are two pressing issues of inextricable global concern requiring unified action,” wrote authors of a new study published Monday in Nature Sustainability. “Continued emissions of GHGs will deplete our collective orbital resource.”
Basically: increasing greenhouse gas concentrations will reduce the number of satellites that we can safely have up in low-earth orbit, or LEO. Companies — primarily Elon Musk’s Starlink — have recently started absolutely flooding LEO with stuff, and that means the potential for a runaway debris disaster like that portrayed in the movie “Gravity” will get more likely as the climate warms. Named after the author of a 1978 paper on the topic, this is known as Kessler Syndrome.
The researchers, from MIT and the University of Birmingham in the UK, found that the “instantaneous Kessler capacity” could decrease between 50 and 66 percent between 2000 and 2100. That’s based on a worst-case emissions scenario which may be relatively unlikely at this point, but that was intentional — when the thing you’re trying to avoid is basically a catastrophic failure of a system, it’s probably good to plan for those worst possible scenarios. Carrying capacity of the thermosphere varies naturally with solar cycles, but just like with plenty of systems down here in the troposphere human-caused emissions are juicing the system: “When adding the contribution of additional GHG emissions, the worst-case scenario capacity carries many fewer satellites across broad swaths of LEO by the year 2100.”
According to the European Space Agency, there are currently 13,660 satellites up in orbit, 11,000 of which are currently operating. Thanks in particular to three events — a Chinese anti-satellite test in 2008, a collision between one derelict and one active Russian satellite in 2009, and Starlink’s huge accumulation of launches starting in 2019 — there are tens of thousands of space objects above 10 cm in size, more than one million between 1 cm and 10 cm, and an astonishing 130 million between 1 mm and 1 cm. And Starlink isn’t slowing down: it has plans to launch as many as 42,000 satellites into space; that’s twice as many as have ever been launched, by anyone, since the Space Age began.
For companies that want a piece of the space-based pie, then, reducing emissions seems like it should be a priority. Or we could end up ruining a bit of space along with the climate down here.
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