Greenhouse Gases

Many chemical compounds found in Earth's atmosphere act as greenhouse gases (GHGs). These gases allow sunlight to pass through the atmosphere; however, when the sunlight is reradiated back toward space as infrared radiation, GHGs absorb the infrared radiation and trap the heat in the atmosphere and at Earth's surface. GHGs allow Earth to be habitable—without them, the average temperature of the planet would be −18 °C instead of 15 °C. However, human actions are increasing the atmospheric concentrations of GHGs, resulting in an enhanced greenhouse effect that is warming Earth's climate and increasing the incidence of extreme weather events.

The most abundant GHGs are naturally occurring: water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). There are also many other, highly potent, ...