The major Greenhouse gases are carbon dioxide, chlorofluorocarbons, methane, nitrous oxide, ozone, and water vapor. The amount of heat trapped depends on the concentration of the Greenhouse gases and how long they stay up in the troposphere. A carbon dioxide molecule stays in the troposphere for 50-200 years. As for CFCs, the source of this Greenhouse gas is leaking air conditions, refrigerators, and aerosols. As for CH4, these molecules are produced when anaerobic bacteria break down organic matter.
Areas where is done include swamps, wetlands, landfills, intestinal tract of cows.
One molecule of methane traps 25 times as much heat as one molecule of carbon dioxide and it stays in the troposphere only 9-15 years. As for N2O, the main source of this gas is fertilizer, it is 230 times more potent than CO2, and stays around for 120 years. This gas is produced primarily from aluminum production and it stays in the troposphere for a very long time anywhere from 2,000-5,000 years. It has been reported that measured atmospheric levels of certain Greenhouse gases have risen substantially in recent decades. The increased levels have be noticed since 1958 and attributed to human activities.