Climate

Abstract

The climate system receives energy from the Sun—mostly in the form of visible light—and balances this energy by radiation of infrared, or heat, energy back to space. Global surface temperature fluctuations are influenced by the amount of solar radiation received at the top of the atmosphere, the reflectivity or albedo, of the planet, and things that affect the efficiency of infrared energy loss to space. The solar radiation received is determined by direct solar output and the Earth‘s orbital fluctuations, and the albedo is largely determined by changes at the surface and by clouds and particles in the atmosphere. Things that affect the efficiency of infrared energy loss to space include both clouds and certain trace gases that absorb outgoing infrared energy and are commonly called greenhouse gases. In order of global importance to the energy balance, these greenhouse gases include water vapor, carbon dioxide (CO₂), methane (CH₄), ozone, chlorofluorocarbons (CFCs), of which CFC-12 dominates, nitrous oxide, and dozens of others. Most of these are long-lived gases, meaning that molecules emitted into the atmosphere tend to remain there for decades and their concentrations are fairly similar throughout the world; important exceptions are water vapor and ozone, which are controlled by a variety of faster processes and therefore have larger variations across the globe and change faster in time.

Northwest Report Chapter Lead Author

Third NCA Northwest Chapter Lead Author