Global climate change
The term greenhouse effect has generally been used for the role of the whole atmosphere (mainly water vapour and clouds) in keeping the surface of the earth warm. Recently however, it has been increasingly associated with the contribution of CO2 which is estimated that contributes about 50% to the anthropogenic greenhouse effect. Additionally, several other gasses such as CH4, CFCs, halons, N2O, ozone and peroxyacetylnitrate (also called greenhouse gasses) produced by the industrial and domestic activities can also contribute to this effect, resulting in a rise of the earth’s temperature. Increasing atmospheric concentrations of greenhouse gasses increase the amount of heat trapped (or decrease the heat radiated from the earth’s surface), thereby raising the surface temperature of the earth. According to Colonbo  the earth’s surface temperature has increased by about 0.6 °C over the last century, and as a consequence the sea level is estimated to have risen by perhaps 20 cm. These changes can have a wide range of effects on human activities all over the world. The role of various greenhouse gasses is summarized in Ref. .
Humans contribute through many of their economic and other activities to the increase of the atmospheric concentrations of various greenhouse gasses. For example, CO2 releases from fossil fuel combustion, methane emissions from increased human activity and CFC releases all contribute to the greenhouse effect. Predictions show that if atmospheric concentrations of greenhouse gasses, mainly due to fossil fuels combustion, continue to increase at the present rates, the earth’s temperature may increase by another 2-4 °C in the next century. If this prediction is realized, the sea level could rise by between 30 and 60 cm before the end of this century . The impacts of such sea level increase could easily be understood and include flooding of coastal settlements, displacement of fertile zones for agriculture toward higher latitudes, and decrease the availability of fresh water for irrigation and other essential uses. Thus, such consequences could put in danger the survival of entire populations.