Two massive, catastrophic problems are set to become one in the near future: Climate change is likely to worsen the issue of space debris, according to a study published in the journal Geophysical Research Letters last month.
Shifts in air density could result in an extra-crowded upper atmosphere, making satellite collisions more likely. What’s more, the recent research projects that, under middle-of-the-road climate scenarios, the upper atmosphere will lose density twice as fast in the future as it has in the past.
“Space debris is becoming a rapidly growing problem for satellite operators due to the risk of collisions,” said Ingrid Cnossen, an atmospheric scientist at the UK’s Natural Environment Research Council and the study’s lead researcher, in a press release from the British Antarctic Survey. “The long-term decline in upper atmosphere density is making [the issue] even worse,” she added.
It’s counterintuitive, but as humans continue to pump greenhouse gases into the lower atmosphere, thereby heating up the surface of our planet, we’re simultaneously making the middle and upper atmosphere cooler. The reasons are multifold, but one big contributing factor is CO2 emissions.
Carbon dioxide molecules readily absorb heat. In the lower atmosphere, that means more molecules slamming into each other and more heat being reflected back to Earth. But in the upper atmosphere, where there are fewer molecules around to begin with, heat-trapping CO2 holds onto energy so tightly that it’s more likely to escape to space than run into another particle and warm up the thin air.
And as the upper atmosphere cools, it’s also losing density. Less dense air means satellites and other space objects orbiting Earth face less drag. Our atmosphere is supposed to be self-cleaning, with objects falling out of orbit and burning up on their way down. However, in a less dense environment, satellites and space trash stay aloft for longer.
Accumulating atmospheric space debris is, on its own, a growing, looming crisis. We rely on satellite infrastructure for communications, research and data collection, and weather forecasting—and we’re rapidly running out of real estate. There have already been some worrying collisions and close calls.
Currently, there are more than 30,000 pieces of track-able stuff circulating in low Earth orbit, according to the European Space Agency. NASA estimates that about 23,000 pieces of debris bigger than a softball are orbiting Earth, and about 100 million teeny-tiny pieces. And every collision creates even more bits of trash. Add in climate change, and crashes could multiply further.
Previous research reached similar conclusions. A 2021 publication, which Cnossen also contributed to, found that objects in low Earth orbit will have lifetimes 30% longer under 1.5 degrees Celsius of global warming, compared with the year 2000.
The recent findings bolster those past conclusions and offer a new quantification of atmospheric change. The upper atmosphere is set to lose heat and density twice as fast over the next 50 years as it has in the past half century, according to the research. This acceleration closely follows the simultaneous expected rise in atmospheric CO2 levels between now and 2070, wrote the study author.
Cnossen relied on computer models to come to that conclusion. She used climate, emissions, and atmospheric data to generate one of the most complete models of climate change across the upper atmosphere to date.
“Changes we saw between the climate in the upper atmosphere over the last 50 years and our predictions for the next 50 are the result of carbon dioxide emissions,” said Cnossen in the press release. For the satellite industry and policymakers, understanding climate change—beyond Earth’s surface— “is increasingly important,” she added.
In follow-up work, the scientist is hoping to explore a wider range of climate and CO2 emission scenarios, to better prepare the world for all possible space junk outcomes.
And ideally, a greater understanding of the problem will lead to meaningful solutions. “I hope this work will help to guide appropriate action to control the space pollution problem,” Cnossen noted in the statement. Ultimately, she wants to “ensure that the upper atmosphere remains a usable resource into the future.”