CO2's Dual Role: Cooling the Upper Atmosphere, Warming Earth's Surface
A recent study has shed light on the contrasting effects of carbon dioxide (CO2) on Earth's atmosphere. While CO2 contributes to warming the planet's surface and lower atmosphere, it simultaneously cools the upper atmosphere, particularly the stratosphere. This phenomenon occurs due to CO2's interaction with different wavelengths of light. Near the Earth's surface, CO2 traps heat that would otherwise escape into space, intensifying warming. However, in the stratosphere, CO2 absorbs infrared energy from below and radiates it into space, leading to cooling. Observations since the 1980s indicate that the stratosphere has cooled by approximately 2°C (3.6°F), a significant change compared to pre-industrial CO2 levels. The study, published in *Nature Geoscience*, aims to provide a quantitative theory for this CO2-induced stratospheric cooling, moving beyond models and estimates to incorporate real-world data and simulations.