Climate change isn’t just causing heatwaves right now, but could eventually lead to a pile-up of space trash in low Earth orbit, NASA warns, with almost three decades of data suggesting a vital layer of our atmosphere is shrinking because of greenhouse gas emissions. An increase in carbon dioxide has led to the upper atmosphere gradually contracting, with a new study putting a number on that change for the first time.
The area of concern is the mesosphere, roughly 30 to 50 miles above the surface of the planet. As carbon dioxide emissions continue, that layer is cooling and thus contracting.
Scientists had been aware of this as a concept for some time, but it’s only with the analysis of 29 years of data across three different satellites that the extent of the shrinking could be calculated. In a new study published in the Journal of Atmospheric and Solar-Terrestrial Physics, Virginia Tech atmospheric scientist Scott Bailey and his team worked out that it’s cooling 4-5 degrees Fahrenheit each decade.
That works out to 500 to 650 feet of contraction over the same period. “Since carbon dioxide also efficiently emits heat, any heat captured by carbon dioxide sooner escapes to space than it finds another molecule to absorb it,” NASA explains. “As a result, an increase in greenhouses gases like carbon dioxide means more heat is lost to space — and the upper atmosphere cools. When air cools, it contracts, the same way a balloon shrinks if you put it in the freezer.”
The mesosphere doesn’t directly impact what’s happening down on Earth’s surface, NASA says, but that’s not to say these outermost fringes of our planet’s atmosphere aren’t vital to things we take for granted. One of the big potential issues is that atmospheric gases at that level are instrumental in what’s known as satellite drag: friction that acts against satellites and other objects in low Earth orbit.
On the one hand, satellite drag is a problem. For objects we want to remain in orbit – such as telecoms satellites like SpaceX’s Starlink – we need to make sure their orbit is continually tweaked to keep them from being tugged out of orbit by the friction. However the flip side is that satellite drag also helps clear space junk and detritus out of the way, disrupting its orbit and encouraging it to burn up on re-entry.
“As the atmosphere contracts, satellite drag may wane,” NASA predicts, “interfering less with operating satellites, but also leaving more space junk in low-Earth orbit.”
There had already been concerns, of course, about just how much trash is building up in orbit around Earth. All satellites, and research platforms further out like the International Space Station, need to have mechanisms by which they can avoid close-calls with passing space junk. An inadvertent collision can be enough to destroy a solar panel or send a satellite spinning off for an untimely reentry, after all.
While the rate of contraction is relatively slow, it does appear to be consistent given the current levels of carbon dioxide emissions. The goal now is to continue tracking the atmospheric shrinkage, amid efforts on the ground to try to curb greenhouse gasses.