The process by which greenhouse gases in the earth's atmosphere absorb infrared radiation from the sun, reflect some of it back into space and emit some of it towards the earth. This natural process provides for relatively stable and mild temperatures on earth and in the atmosphere. However, human activity can change the concentration of greenhouse gases in the atmosphere, which can amplify the greenhouse effect.
"Glossary and Abbreviations", Barnsley, Ingrid, United Nations University Institute of Advanced Studies (UNU-IAS) 2009, "UNUIAS Guide, Reducing Emissions from Deforestation and Degradation in Developing Countries (REDD): A Guide for Indigenous Peoples." January 2009 http://www.ias.unu.edu/resource_centre/2009_REDD_Guide.pdf
Warming of the earth's atmosphere caused by a build-up of carbon dioxide and other greenhouse or trace gases that act like a pane of glass in a greenhouse, allowing sunlight to pass through and heat the earth but preventing a counterbalancing loss of heat radiation.
United Nations (1997): Glossary of Environment Statis tics. Studies in Methods, Series F, No. 67