Source: AIE / OECD, 1990.

Contribution of Man-Made Gases to the Greenhouse Effect

The greenhouse effect is not by itself a pollutant, but the result of the combined actions of several greenhouse gases (notably carbon dioxide). The atmosphere is generally permeable to short wave radiations. Those radiations are reflected by the earth surface as infrared radiations, which greenhouse gases absorb and re-emit towards the surface. There is thus a higher capacity of the atmosphere to retain heat. The greenhouse effect is an indirect consequence of carbon dioxide (about 71% of the contribution), CFCs (3%), ozone, and HC/VOC emissions, notably methane (8%), of which transportation contributes significantly. Little is known on how global warming will affect regional/local environmental conditions. Most studies focused on global effects like the rise of sea levels.

Gas	Potential to retain infrared rays compared to carbon dioxide	Pre-industrial era concentration (in ppm)	Actual concentration (in ppm)
CO2	1	275	346
Methane	25	0.75	1.65
CFC (R12)	20,000	0	0.0004
CFC (R11)	17,500	0	0.00023
N2O	250	0.25	0.35

Source: AIE / OECD, 1990.

The greenhouse effect contributes to global warming. Since 1850, as the levels of carbon dioxide increased by 25% and the average temperature on earth increased by one degree Celsius. By 2050, an additional rise between 1.5 and 4.5 degrees Celsius could occur. This may cause fluctuations in weather systems with changes in regional and seasonal weather patterns that will have significant effects on the ecosphere, particularly for agriculture. Rise in sea levels is a potential problem for coastal areas where most human activities are located. In some areas, a rise of one meter may flow substantive surface of land. It may indirectly affects sea current patterns and fishing.