The warming of the atmosphere that occurs when heat (longwave infrared radiation) is absorbed and re-radiated by greenhouse gases. When people add greenhouse gases to the atmosphere, Earth’s temperature rises.
Where does the name “greenhouse effect” come from?
Greenhouses are glass houses where people grow plants year-round, no matter how cold it gets outside. The glass walls and roof of a greenhouse let short-wave solar radiation in and trap re-radiated infrared radiation (heat). Unlike the atmosphere, however, the walls of a greenhouse keep the warmer air inside from circulating, or mixing, with cooler air outside. A greenhouse may not be the perfect analogy, but the name has stuck!
Learn more about the greenhouse effect.