Meteorologist: Solar Activity, Not CO2 Emissions, Driving Satellite Collision Risk

A recent article from Smithsonian Magazine (SM) titled “Climate Change Might Increase Satellite Collisions, Limiting How Many Can Safely Orbit Earth, Study Finds” claims that human-induced climate change is causing the upper atmosphere to contract, reducing drag on satellites and space debris, which could lead to more collisions. [emphasis, links added]

This is misleading if not outright false.

Multiple studies show the dominant factor influencing the density and temperature of the upper atmosphere—where some satellites orbit—is solar activity, not carbon dioxide (CO2) emissions.

Data from decades of space research confirm that variations in solar radiation, particularly changes in ultraviolet (UV) output and solar wind, have far greater impacts on atmospheric density than any CO2-driven effects.

The study, referenced by the SM article, is summarized as:

“The thermosphere, which begins around 50 miles (80 kilometers) above Earth’s surface, is contracting. This is because as greenhouse gases like carbon dioxide and methane accumulate in the lower atmosphere, they radiate heat into space and cause the upper atmosphere to cool and shrink.”

This claim exaggerates the role of human greenhouse gas emissions while ignoring the well-documented influence of solar variability.

The thermosphere, seen in the graphic below from The Canadian Space Agency, is primarily heated by the Sun’s intense ultraviolet radiation, and its temperature and density fluctuate significantly in response to the 11-year solar cycle.

When solar activity is high, the thermosphere expands, increasing drag on satellites and space debris. Conversely, during solar minima, the thermosphere contracts.

These natural solar-driven variations completely overshadow any potential effect from anthropogenic CO2.

A study in the Journal of Space Research confirms that thermospheric temperature fluctuations are overwhelmingly linked to solar output, not greenhouse gases.

Similarly, research in Space Weather Science demonstrates that solar activity is the primary driver of upper atmospheric density changes, affecting satellite drag far more than any CO2-related cooling.

In addition, a report in EOS shows that during a weaker-than-normal solar cycle, the thermosphere cooled and contracted more than expected.

This aligns with long-term observations that solar variability dictates thermospheric behavior. NASA also credits the sun as driving the changes in the thermosphere.

While many satellites orbit Earth in the thermosphere, most Earth-orbiting satellites reside in the exosphere, such as geostationary satellites with orbits at 22,500 miles even higher than the exosphere, the outermost layer of the Earth’s atmosphere, where the atmosphere thins out and merges with outer space.

So, the concerns about the thermosphere in the SM article are mostly moot, especially since many satellites that orbit in the thermosphere can boost with thrusters to a higher orbit if needed. Engineers plan for this.

The SM article also fails to consider historical data.

If CO2 were truly the primary driver of thermospheric contraction, we would expect to see a steady, predictable decline in atmospheric density as CO2 emissions have increased.

Instead, we observe clear cyclical patterns that correspond with the 11-year solar cycle, not industrial CO2 emissions. During past solar minima, such as the Dalton Minimum (1790–1830) and the Maunder Minimum (1645–1715), similar thermospheric contractions occurred—long before human activity significantly increased CO2 levels.

By pushing a climate change-driven explanation while ignoring the Sun’s dominant role, and ignoring where most satellites orbit Earth, Smithsonian Magazine is misrepresenting what science tells us about the atmosphere and what drives change in it.

Space debris is a real issue that requires attention, but CO2 neither creates space debris nor makes collision with such debris more likely.

Blaming CO2 emissions for upper-atmospheric changes is a false narrative and distracts attention from the real problem of how to handle space debris.

Read more at Climate Realism