Green-house effect : Usually carbon dioxide is not considered as pollutant, but its higher concentration forms the thick layer above the earth surface which checks the radiation of the heat from the earth surface. Because of this the temperature of the earth surface increases. This is called as “**Green house effect”.**
The various green house gases are CO2 (Warming effect 60%), CH4 (warming effect 20%), chlorofluoro carbon or CFCs (14%) and nitrous oxide/N2O (6%.)
