GHG Emissions’ Effects on the Atmosphere and Satellites

Research on the impacts of greenhouse gases (GHGs) in the atmosphere primarily focuses on the troposphere, the lowest layer of the Earth’s atmosphere and in direct contact with the Earth’s surface.

The troposphere is where most weather phenomena occur, making its study crucial for understanding how changes in this region will affect all aspects of life on Earth.

However, greenhouse gas (GHG) emissions impact the Earth’s surface and the region above the troposphere. Recently, there has been a significant increase in the use of satellites in low Earth orbit (LEO) for various purposes, including communications, weather forecasting, navigation, and defence.

Currently, around 11,900 satellites are orbiting Earth, supporting these services and increasing our dependence on the long-term sustainability of this region.

The Earth’s thermosphere extends into LEO, and changes in the upper atmosphere caused by greenhouse gases must be considered when planning future satellite operations. A study published in Nature Sustainability and led by researchers at MIT, “Greenhouse Gases Reduce the Satellite Carrying Capacity of Low Earth Orbit,” reports that carbon dioxide and other greenhouse gases can shrink the upper atmosphere. One atmospheric layer of particular interest is the thermosphere, where the International Space Station and most satellites operate.

The thermosphere naturally shrinks and expands in response to the sun’s output during an 11-year solar cycle. However, the study has found that greenhouse gases intensify the contraction of this layer, resulting in reduced densities at high altitudes.

When the thermosphere contracts, the decreasing density also lowers the atmospheric drag. This reduction in drag allows defunct satellites and space debris to remain in orbit longer than they usually would.

Drag functions similarly to air friction, pulling space junk and old satellites down to lower altitudes where they eventually burn up, effectively cleaning up debris from orbit. Fewer burns mean more junk is allowed to clutter space, heightening the risk of satellite collisions.

The thermosphere naturally shrinks and expands over an 11-year solar cycle, influenced by the sun’s output. However, the study found that greenhouse gases intensify the layer’s contraction, reducing densities at high altitudes.

To assess how this phenomenon will affect the carrying capacity of satellites in low Earth orbit (LEO), scientists used computer models to simulate the impact of greenhouse gases on the thermosphere and satellite orbits. They concluded that future carbon dioxide emissions will heavily influence this impact.

By 2100, the satellite carrying capacity in the busiest regions of low Earth orbit could decline by approximately 50 to 66%, or even by 82% in a worst-case scenario.

These findings indicate that greenhouse gas emissions on Earth over the past century are shaping how we will operate satellites in the next century. Additionally, due to the significant increase in the number of satellites launched, failing to address this issue may lead to the risk of Kessler syndrome. In this phenomenon, a chain reaction of collisions renders space unusable.

Learn more about the study by browsing the “Sources” section below.