How climate change could make Earth's space junk problem even worse

Growing concentrations of greenhouse gases are making the upper atmosphere thinner, decreasing its ability to pull space junk out of orbit. As a result, far fewer satellites will be able to safely operate in near-Earth space in the coming decades, with local space debris emergencies likely to become a norm, a new study suggests.

Scientists have known since the 1990s that complex processes taking place in Earth's atmosphere because of climate change could reduce the density of the upper layers of the planet's gaseous shroud. When the upper atmosphere becomes thinner, satellites and old space junk encounter less drag as they hurtle around the planet. They therefore stay afloat longer, and the lower regions of space become more cluttered. Over the past decade, studies have emerged estimating how much exactly these atmospheric changes affect those satellites.

A team of aerospace engineers at the Massachusetts Institute of Technology (MIT) has now taken a deeper dive into the problem and estimated the knock-on effects of this reduced drag on safety of orbital traffic. The results are astounding: By the end of this century, some orbital regions might be able to safely carry up to 66% fewer satellites than they do today because of the increasing amount of space junk.

The discovery comes at an important juncture in humankind's use of space. With the proliferation of large satellite constellations such as SpaceX's Starlink or Amazon's Project Kuiper, the quantity of satellites in orbit is set to skyrocket. Yet, what the scientists call the "satellite carrying capacity" of low Earth orbit will dwindle, unless greenhouse gas emissions are significantly curbed.

Related: The Kessler Syndrome and the space debris problem

"The megaconstellation is a new trend, and we're showing, because of climate change, we're going to have a reduced capacity in orbit," study co-author Richard Linares, associate professor in MIT's Department of Aeronautics and Astronautics (AeroAstro), said in a statement. "And in local regions, we're close to approaching this capacity value today."

The researchers analyzed individual orbital altitudes and found that some of these shells are already reaching the limits of their carrying capacity, threatening to spawn local runaway space debris collision cascades. Such cascades would produce further fragment clouds that would further decrease the safety of orbital traffic.

All is not lost, however: Humankind has a chance to thwart the trend by making sure greenhouse gas concentrations in the atmosphere stop rising.

"Our behavior with greenhouse gases here on Earth over the past 100 years is having an effect on how we operate satellites over the next 100 years," Linares said.

The study's lead author, William Parker, a graduate student at AeroAstro, added: "The upper atmosphere is in a fragile state as climate change disrupts the status quo. At the same time, there's been a massive increase in the number of satellites launched, especially for delivering broadband internet from space. If we don't manage this activity carefully and work to reduce our emissions, space could become too crowded, leading to more collisions and debris."

The study was published in the journal Nature Sustainability on Monday (March 10).