greenhouse effect, a theorized change in the earth’s climate caused by accumulation of solar heat in the earth’s surface and atmosphere. Human activity contributes increasing amounts of the so-called greenhouse gases, such as carbon dioxide, methane, and chlorofluorocarbon, to the atmosphere. Some of the particles and gases in the atmosphere also allow more sunlight to filter through to the earth’s surface but reflect much of the radiant infrared energy that otherwise would escape through the atmosphere back into space. See also global warming.
