The Impact of Climate Change on Earth’s Upper Atmosphere and Satellite Capacity

Climate change is not only affecting Earth’s oceans, wildlife, and agriculture, but also its surrounding space. Recent research has investigated the effects of greenhouse gases on the upper atmosphere, suggesting that it will contract over time and become less capable of holding as many satellites as it currently does.

Using simulations of carbon emissions over time, a team of scientists from MIT has predicted a significant drop in the satellite-carrying capacity of low Earth orbit. They found that as the uppermost atmosphere shrinks, debris will remain in orbit longer, and the resulting reduction in atmospheric drag could increase the risk of collisions in space. According to a study published in Nature Sustainability, the carrying capacity of the most popular regions could be reduced by 50 to 66% by the year 2100 due to the effects of greenhouse gases.

William Parker, a graduate student at the department of aeronautics and astronautics at MIT, explained that “as greenhouse gas concentrations rise, they warm the troposphere where we live but cool and contract the upper atmosphere—the stratosphere, mesosphere, and thermosphere.” The thermosphere plays a crucial role in creating drag on orbital debris, gradually removing it from space. However, as the atmosphere contracts due to increasing greenhouse gas emissions, debris remains in orbit longer, increasing the risk of a runaway cascading collision scenario.

The thermosphere is home to the International Space Station and most other satellites orbiting Earth, with over 10,000 satellites currently drifting through low Earth orbit. As emissions rise, the chances of collision between spacecraft increase, leading to the creation of more space debris and reducing the number of satellites that can operate in low Earth orbit within the same risk threshold as today.

Greenhouse gases act like a blanket, warming the troposphere by insulating the surface and reflecting heat back toward the ground, Parker explained. The retention of heat in the troposphere means less heat reaches the upper atmosphere, and the heat that does make its way there is radiated out into space by greenhouse gases. “These two contributions lead to long-term cooling in the stratosphere, mesosphere, and thermosphere, which leads to contraction,” Parker added. “If you put a balloon in a freezer, it shrinks as the temperature drops; the same thing is happening to the upper atmosphere on a global scale.”

The researchers behind the study simulated different scenarios over the coming century, including one where greenhouse gas concentrations remain at the same level as in the year 2000 and others where emissions change according to the Intergovernmental Panel on Climate Change (IPCC) Shared Socioeconomic Pathways (SSPs). The increase in emissions over time led to a significantly reduced carrying capacity through low Earth orbit.

“Without an atmosphere, most space debris would remain in orbit indefinitely,” Parker said. “As the atmosphere thins, debris lingers longer, increasing the risk to active satellites. With the growing consequences of space debris, we can accommodate fewer debris-generating events.” The study warns that if satellite capacity is exceeded in a particular region, it may lead to a “runaway instability,” or a cascade of collisions that would create so much debris that satellites would no longer be able to safely operate there.

As the space industry continues to grow at unprecedented rates, so does the demand for spacecraft in Earth orbit. In 2023, there was a 35% increase in the total number of active satellites orbiting Earth, and this number is likely to increase over time.

The researchers behind the study suggest that proactive measures need to be taken today, including better decisions about the number of satellites being launched into space. “More satellites have been launched in the last five years than in the preceding 60 years combined,” Parker said. “One of the key things we’re trying to understand is whether the path we’re on today is sustainable.”