State of the Science Fact Sheet: Greenhouse Gases and Climate

Greenhouse gases (GHGs) are several of many gases in Earth's atmosphere. Their unique feature is their ability to trap heat in the form of radiation (Figure 1), thereby maintaining the Earth’s atmosphere at a habitable temperature - a process known as the greenhouse effect. Levels of GHGs in excess of those present due to natural cycles disturb Earth’s energy balance and change climate, including raising atmospheric temperature and altering rainfall patterns. Since the industrial revolution, atmospheric concentrations of GHGs, especially CO2, N2O, and CH4, have been increasing due to extraction and burning of fossil fuels and land use changes. About half of the excess emission of CO2 is absorbed by the terrestrial biosphere and the ocean (where it leads to ocean acidification). Although all GHGs are present in the atmosphere in trace amounts (collectively less than 0.05%), some of the most abundant ones are CO2 and CH4, while some of the most potent ones are CFCs.