Upper atmosphere

Theoretical understanding of the upper atmosphere and the complex physical processes responsible for its composition, dynamics, and thermal behavior has improved to the point where reasonable three‐dimensional, time‐dependent models of the atmosphere above about 100 km exist. These models have been extensively refined through comparisons with experimental data from coordinated, multistation ground‐based investigations. Theoretical calculations using a state‐of‐the‐art model of the upper atmosphere indicate that over the next century, the anthropogenic production of CO₂ , which is anticipated to warm the lower atmosphere, will also cool the upper atmosphere. The model predicts that doubling atmosphere CO₂ cools the mesosphere (80–100 km) by about 10°C and the thermosphere (above 100 km) by about 50°C.