15.5.4 Green House Effect (Global Warming)
In 1987, Jean Baptiste Fourier
a French mathematician and scientist coined the “Green House Effect” for trapping of heat in the atmosphere by
certain gases. This effect is termed
as Global Warming.
Green house is a building made
of glass, with heat and humidity regulated for growing plants. The atmosphere
acts like a glass in a green house. It absorbs some of the long wave radiation
emitted by the earth and radiates the energy back to the earth and thus
maintains earth’s temperature .
Greenhouse effect may be
defined as “The heating up of the earth
surface due to trapping of infrared radiations reflected by earth’s surface by
CO2 layer in the
The major green house gases besides CO2
are CH4, CFC, N2O, Ozone and water vapours. Heat
retaining capacity of greenhouse gases
are called Global Warming Potential(GWP).The GWP based sequence of greenhouse gases is as CFC>N2O>CH4>CO2.
Major green house
gases and their sources are listed in the following table 15.2
Contribution to global warming
Carbon dioxide (CO2)
1) Fossil fuel combustion (coal, oil,
2) Deforestation and land use
1) Biomass burning and garbage landfills.
2) Leakage of gases from coal mines
and natural gas.
1) Refrigeration and air conditioning.
2) Aerosols (spray propellants).
3) Plastic foams.
4) Industrial solvents.
Nitrous oxide (N2O)
1) Fertilizer use.
2) Combustion of fossil fuels
3) Biomass burning.
Table 15. 2 Green house gases
Increase in average temperature of the earth
surface due to green house effect is called Global Warming. The earth’s atmosphere acts like a greenhouse and CO2 acts like glass windows. CO2
and water vapours in the atmosphere allows short wavelength solar radiation but
reflect the longer wave length heat radiation from warmed surface of the earth.
CO2 is transparent to sunlight but not the heat radiation. So they
trap and reinforce the solar heat stimulating effect which is known as Green House effect.