Researchers from Columbia Climate School have unveiled new findings explaining one of climate science’s long-standing mysteries: how rising levels of carbon dioxide cool the upper atmosphere while simultaneously warming the Earth’s surface and lower atmosphere. The study was published in Nature Geoscience.
Scientists say the phenomenon is linked to the way CO2 molecules interact with infrared light at different atmospheric levels. In the lower atmosphere, carbon dioxide traps heat that would otherwise escape into space. In the stratosphere, however, CO2 behaves differently by radiating part of that energy back into space, causing the upper atmosphere to cool.
The research team, led by Sean Cohen alongside Robert Pincus and Lorenzo Polvani, developed mathematical models to better understand the mechanics behind this process. Their work identified specific infrared wavelengths that become increasingly effective at releasing heat from the stratosphere as CO2 concentrations rise.
According to the study, the Earth’s stratosphere has cooled by around 2 degrees Celsius since the mid-1980s, a trend largely attributed to human-generated carbon emissions. Researchers also found that while ozone and water vapor contribute slightly to the process, carbon dioxide remains the dominant factor behind stratospheric cooling.
