Nitrous oxide, methane and carbon dioxide are the major gases that enhance the greenhouse effect by capturing reradiated infrared radiation from the Earth's surface and subsequently warming the troposphere (lower atmosphere). Atmospheric levels of all three have been growing due to human activities. Once released, they remain as greenhouse gases in the biosphere for very long periods of time.
http://climatechange.lta.org/wp-content/uploads/cct/2015/02/GHGases.jpg
http://climatechange.lta.org/get-started/learn/co2-methane-greenhouse-effect/
