Recent findings show that carbon dioxide not only pollutes and warms the atmosphere but also contributes to a measurable reduction in the thickness of the upper layers. A new study provides scientific confirmation that greenhouse gases have played a significant role in the shrinkage of the upper atmosphere, a possibility discussed for many years but now verified with solid data.
The research focused on two atmospheric layers collectively known as the middle and upper mesosphere and lower thermosphere, often abbreviated as MLT. The mesosphere begins roughly at 60 kilometers above the surface, while the lower thermosphere starts around 90 kilometers. These zones are critical for understanding how energy and mass move through Earth’s atmosphere and how changes at lower levels can ripple upward and outward.
Data from NASA’s TIMED satellite, an observatory dedicated to monitoring the upper atmosphere, provided a rich dataset. Over nearly two decades, from 2002 to 2021, TIMED tracked pressure and temperature in the MLT layers. This long-running record allowed scientists to see patterns and trends that emerge only with sustained measurements, offering a rare look at how the upper atmosphere behaves over time.
Analyses of the data show a radiative cooling effect in the upper atmosphere driven by carbon dioxide. When CO2 radiates heat into space more efficiently, it cools the layers above. This cooling causes the stratosphere to contract and similarly compresses the mesosphere and thermosphere. The result is a measurable thinning of these high-altitude regions, a phenomenon that becomes more pronounced with continued emissions of greenhouse gases from human activities.
Using satellite measurements, researchers led by Mlynczak concluded that the mesosphere and the lower thermosphere together thinned by about 1,333 meters in total. Of this, approximately 342 meters can be attributed to cooling from human-caused CO2 releases. While the thermosphere spans hundreds of kilometers, a few hundred meters of thinning may seem modest. Yet modeling work suggests important consequences for how the upper atmosphere interacts with the rest of the system. In fact, a September study from Ingrid Cnossen of the British Antarctic Survey in England indicates that cooling in the thermosphere could reduce atmospheric friction by as much as about one-third by 2070, altering satellite dynamics and atmospheric drag in meaningful ways.
Implications for satellites and space debris
These changes carry implications for objects in orbit around Earth. The cooling-driven contraction of upper layers can influence the behavior and lifetime of space debris, including older satellites and other pieces of space junk that share near-Earth space. If atmospheric drag decreases, debris may remain in higher orbits longer than before, shifting risk profiles for active satellites and crewed space stations. This effect could complicate mission planning and orbit maintenance for future launches and operations in space near Earth.
With debris staying in orbit longer, the likelihood of collisions could rise if orbital paths are not carefully managed. In turn, this affects the reliability and safety of satellite networks used for communications, navigation, weather observation, and research. The broader consequence is a need for updated strategies in orbital debris mitigation and sustainable space traffic management as the upper atmosphere continues to respond to ongoing greenhouse gas emissions.
One notable takeaway is that some satellites may remain operational for extended periods, which can be beneficial for users who rely on continuous satellite services. At the same time, the persistence of space debris may necessitate more frequent orbital adjustments to avoid potential collisions and to keep critical assets in their designated orbits. These dynamics underscore the interconnectedness of atmospheric science, space operations, and climate policy, reminding observers that changes high above our planet can have tangible effects on everyday technology and research capabilities.
Researchers emphasize the importance of continued observation and modeling to refine predictions of upper-atmosphere response to greenhouse gas changes. Ongoing data collection and the development of more sophisticated models are essential to anticipate future shifts in drag, satellite lifetimes, and the behavior of space debris. This work helps inform both climate science and space safety planning, linking the fate of the atmosphere to practical considerations in orbital management and technology deployment.
Reference work: A peer-reviewed study documenting the satellite-based findings and the cooling effect of carbon dioxide on the MLT layers is cited to ensure scientific transparency and reproducibility. [Attribution: Journal of Geophysical Research or equivalent peer-reviewed source, 2022].
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Note: This article summarizes scientific observations and their implications for satellite operations and space safety. It does not include contact details or external sources beyond cited attribution to the originating research publication.