Carbon dioxide emissions impact the atmosphere far beyond warming alone. New research indicates that these gases contribute to a measurable shrinking of the upper layers of Earth’s atmosphere. While the idea has floated for years, scientists have now gathered evidence showing that elevated CO2 levels can cause the upper atmosphere to contract, particularly in the regions known as the mesosphere and the lower thermosphere.
The study concentrates on two atmospheric layers collectively called the MLT. The mesosphere begins roughly 60 kilometers above the planet’s surface, while the lower thermosphere starts around 90 kilometers. These regions are critical for understanding how energy and radiation move through the upper atmosphere and how human activities may influence it.
Researchers relied on data from NASA’s TIMED satellite, a platform dedicated to monitoring the upper atmosphere. Over nearly two decades, from 2002 to 2021, TIMED provided detailed measurements of pressure and temperature in the MLT layers. This long-running dataset allowed scientists to observe subtle trends and build a more complete picture of atmospheric cooling processes at high altitudes.
The analysis shows that radiative cooling in the upper atmosphere is linked to carbon dioxide. As CO2 radiates heat more efficiently into space, the associated cooling causes the stratosphere, and with it the mesosphere and thermosphere, to contract slightly. This chain of effects means the overall vertical extent of the upper atmosphere is reduced by a measurable amount, a finding that carries implications for aeronomy and satellite dynamics.
The researchers quantified the total contraction of the mesosphere and the lower thermosphere at about 1,333 meters. Of this, approximately 342 meters are attributable to cooling driven by human-made CO2 emissions. While hundreds of meters may seem modest given that the thermosphere spans several hundred kilometers, the consequences are not trivial for space operations.
In a broader context, the cooling and contraction of the upper atmosphere could alter the density profile encountered by orbiting objects. Some projections suggest that reduced upper-atmosphere drag may extend the lifetimes of space debris and aging satellites. In practical terms, this means debris and older spacecraft could remain in orbit longer unless active tracking and orbital corrections are performed, which raises considerations for mission planning and space traffic management.
Implications for satellites and space junk
The extended residency of objects in orbit could affect the dynamics of debris fields and affect new satellite deployments. Operators may need to adjust satellite design, propulsion strategies, or orbital regimes to mitigate collision risks and ensure reliable space-based services. Ongoing observations and modeling help agencies and researchers anticipate these changes and adapt accordingly. This line of inquiry is part of a broader effort to understand how human activity influences the near-Earth environment and what it means for space operations and observations.
One notable takeaway is that satellites may remain active for longer periods, which has both practical and operational benefits. Yet at the same time, the persistence of space objects increases the probability of encounters with other debris, underscoring the importance of robust collision avoidance and debris-removal strategies. The research fits into a growing body of evidence about how greenhouse gases can alter high-altitude physics in ways that matter for technology and exploration.
In summary, the study highlights a direct link between anthropogenic CO2 and measurable changes in upper-atmosphere thickness. The findings underscore the interconnectedness of climate processes and space environment dynamics, offering valuable insights for satellite operators, policymakers, and scientists monitoring the near-Earth space arena.
Reference work: citation details are available in the published study for qualified readers and researchers who wish to explore the methodology and data more deeply.