GLOBAL WARMING

                                     GLOBAL WARMING

                    Global warming is heating of earth's climate system it  caused by the pre-industrial period (between 1850-1900) due to human activities,burning of fossil fuel which increases heat close in to green house gas levels in earth's atmosphere.

GREEN HOUSE EFFECT:

              The atmosphere is able to keep the earth habitable because some of its constituent gases can absorb heat radiation from the earth’s surface preventing it from escaping into space. These gases are called as greenhouse gases (GHGs).This heat trapping phenomenon is known as greenhouse effect. It is a natural phenomenon without which earth would be to too cold to support life.

Some of the sun’s rays that penetrate the layer of carbon dioxide strike the earth and are converted into heat.The heated earth re-radiates this absorbed energy as radiations of longer wavelengths, much of this does not pass through carbon dioxide and water vapor in the atmosphere and adds to the heating of the earth's atmosphere.

There are several greenhouse gases, the major and important ones are carbon dioxide (CO2), methane (CH4), chlorofluorocarbons (CFCs), nitrous oxide (NOx) and ozone (O3).carbon dioxide and  methane are produced by natural as well as man-made sources while others such as CFCs are purely man-made.

CAUSES OF GLOBAL WARMING:

CARBON DIOXIDE(CO2):

The single largest contributor to the global greenhouse effect is CO2 which is produced wherever fossil fuels are burnt. It has been estimated that by mid-1700 the average CO2 level in the earth’s atmosphere was 280 ppm that stood 315 ppm by 1988 (which is about 375ppm as of now) and by the middle of 2050 if the current rate of fossil fuel burning continues, it is likely to reach 600 ppm. 

METHANE(CH4):

           Another important greenhouse gas which could affect the climate of the earth is methane. It is significant to note that the gas is only about 5% of that CO2 , but it is 20-30 times more effective than that of CO2 in producing greenhouse effect.

Most methane is produced by natural biological processes such as bacterial action in the gut of cattle and other ruminants, in Paddy puddle fields, marshy lands, garbage dumps and landfills. To some extent it is also produced by mining of coal and oil distribution of natural gas. 

Leakage of natural gas from pipelines or geological fissures also contributes to the atmospheric methane level. In mid-1700 the concentration of methane averaged 800 ppm and stood at 1700 ppm 1988. It is rising at the rate of 1-2% a year.

CHLOROFLUOROCARBONS(CFCs):

The third major greenhouse gas is a group of synthetics, called chlorofluorocarbons (CFCs) and these versatile chemical were manufactured only in 1960s.They are used extensively as refrigerants, plastic foaming agents, aerosol propellants and cleaning agents. CFCs first attracted the attention of scientists in 1970s when it was discovered that they could have destructive effects on the stratospheric ozone layer.

As a greenhouse gas, it is twenty thousand times as powerful as CO2. Moreover, they are extremely persistent and can remain in the stratosphere for decades the present level is 700 ppm and is rising at 5% a year.

Although CFCs stand after CO2 In their contribution to global warming but their atmospheric concentrations are extremely small.CFCs once released in to atmosphere, persists for hundred years. Americans are successful in recapturing the CFCs present in the atmosphere.

NITROUS OXIDE:

Nitrous oxide is yet another greenhouse gas.It is produced by burning of coal, oil and biomass along with CO2. It is also released from nitrogen based fertilizers applied in agricultural soils. 

During the pre-industrial period, the atmospheric level  of nitrous oxide was 280 ppm which stood to 310 ppm in 1988.The present level is around 330 ppm and rising at 0.3 % to 0.4 % every year.

Measures to reduce the buildup of GHGs

 The suggested measures are as follows:

1.Improving the efficiency of energy production and use

2.Consumption of less carbonaceous fuels, switching up from carbon – intensive fuels such as coal to       hydrogen – rich fuels, such as natural gas

3.Rapid development of carbon free energy sources, such as solar, wind, tidal, geothermal and nuclear       energy.

4.Total ban on production and use of CFCs

5.Halting deforestation and encouraging massive afforestation and reforestation.

6. Many countries that “atmosphere” is a common heritage of human kind and need to be protected.