Carbon dioxide concentrations have increased in the uppermost reaches of the atmosphere over the past eight years, reports a paper published online this week in Nature Geoscience. The increase could explain a recently reported reduction in upper atmospheric pull on satellites and space debris.
Although carbon dioxide warms the surface of the Earth, it cools the atmosphere above an altitude of about 50 km, reducing upper atmospheric density and thus the pull on man-made objects orbiting the Earth. John Emmert and colleagues used satellite data to assess changes in carbon dioxide concentrations at an altitude of 101 km between 2004 and 2012. They show that carbon dioxide concentrations rose significantly over this time frame, potentially due to an increase in atmospheric mixing and transport.
In an accompanying News and Views article, Stefan Noel suggests that the finding “provides a glimpse into the impact of anthropogenic carbon dioxide emissions on the upper reaches of the atmosphere”.