GREEN HOUSE EFFECT INTRODUCTION In temperate countries some economically important plants that cannot grow outside at a very low temperature during the winter are grown in glass-walled & glass-roofed growth chambers (known as glass houses) exposed to sunlight. Glass houses are also used in sub tropical regions during winter months & relatively cold high altitude for high value horticultural annual crops including flowers on a commercial scale as well as for research work especially for breeding of new varieties & crop physiological & pathological studies. Temperature within the glass house rises because of the glass of the roof & walls through it allows entry of sunlight with little obstruction, resist the escaping of the reflected light of longer wave-lengths rich in infra-red rays resulting in a heat built up. Such glass houses are called green houses as the light & heat within such houses prove very effective for profuse growth of green plants. The property of trapping heat by carbon di oxide & other gases of the atmosphere is similar to the glass cover of green house that resists the escaping of heat radiated from inside of the house. As such, these atmospheric gases are called green house gases that resist the escaping of radiated heat from the earth by absorbing infra red rays & particularly reflecting the trapped heat back to earth's surface.

this phenomenon is therefore called the green-house effect in witch certain atmospheric gases act in a manner similar to the glass cover of glass house, as earth itself act as a green-house. MAJOR GREEN HOUSE GASESThe major sources of green house gases are (i) CARBON DI OXIDE - It comes from burning of fossil fuels &from deforestation. (ii) METHANE- It comes from paddy field, burning of wood, wetland etc. (iii) CHLOROFLURO CARBONS -which is popular known as CFC.

It comes from air conditioning industry, foam packaging industries. (iv) NITROUS OXIDE-It comes from coal burning, motor, breakdown of chemical fertilizer, biomass burning. Carbon-di-oxide is the major green-house gas responsible for more than 55% of the green-house-effect. Methane is responsible for 20%, CFC is responsible for 15% & NO is responsible for 5% of the green-house effect. If the amount of carbon-di-oxide & other green-house gases would increase in the atmosphere, the temperature on the surface of the earth & that of the layers of air to the surface would increase, on the other hand global temperature would increase with the decrease in amount of the green house gases in the atmosphere. In fact the amount of all the green-house gase in the atmosphere is gradually increasing, as a result of which it is predicted that the global temperature would increase & there would be climatic changes on the earth resulting in adverse effects on the ecosystem of earth.

We should therefore, well apprise ourselves of the green houses gases & or about the decrease or increase in the amounts of these gases in the atmosphere. POSSIBLE EFFECTS OF INCREASED GREEN HOUSE GASAESA possible direct effect on the of an increase in the amounts of green house gases in the atmosphere would be an increase in the average temperature of earth's surface & its layers of air. But there is a difference of opinion among the scientists regarding the extent to which such temperature would increase & how rapidly such a change in global temperature would take place. The predicted rise of global temperature may appear to be not too high, but if it actually increases as predicted, the impact may be very high. It has been apprehended the if the global temperature increases by only 3 degree celsius above the present temperature, a situation will arise which the living world did not face during the last 100000 years. With a rise in global temperature there may be other consequential effects.

Some possible effects are discussed below. POSSIBLE EFFECTS ON CLIMATIC CONDITIONS Emission of green house gases in the atmosphere in increasing rates may effect the climate to a large extent. Due to an increase of average global temperature, water from various sources on earth may evaporate more rapidly as a result of which the overall amount of rainfall may increase. But this phenomenon will not occur evenly in all parts of the world, in some regions specially in the tropical zones the summer may be prolonged, on the other hand in the north polar regions the temperature of the earth's surface & its adjacent air layers in the winter may be much higher compared to present situation.

POSSIBILITY OF RISING OF SEA LEVEL If the global temperature increases the ice-caps & the glaciers of polar regions of the earth (Greenland, Antartica) may be melted partially, the floating ice on the water of the seas may also melt partially or completely & due to an increase in temperature there may be an increase in volume of sea water as a result of which the level of sea water may rise. The problem of rehabilitation of the victim as of flood may become acute in many countries. Besides fertile agricultural lands of such areas being flooded with suitable water may become unsuitable for cultivation badly effecting the production of crops. It is not difficult to presume that in case such a situation actually arises the worst sufferers will be the por countries in the third world. With a rise of sea water level the low land areas of the deltas will face the maximum probability of being flooded with or being permanently immersed in sea water. Most of the low lying costal cities like Kolkata, Dhaka will be inundated.

Low lying areas of different countries of the world will be flooded by salt water causing residential & food problem. EFFECTS ON AGRICULTURAL PRODUCTION It has been apprehended that due to intensive green house effect thee may be frequent droughts in summer in countries of middle latitudes of the north hemisphere, in that event production of crops may decrease in the northern parts of USA & in the present productive areas of the erstwhile U. S. S. R. On the other hand, the amount of carbon di oxide in the atmosphere being doubled & the average global temperature rising thereby, production of wheat may increase by 33% in the middle European regions or erstwhile USSR but the production of barley may decrease to a considerable extent as because higher temperature is unfavourable for its production.

An increase in the amount of car on di oxide in air is favourable for an increasing rate photosynthesis in plants, thereby increase in carbon di oxide may increase the production of crops in some cases, on the other hand crop production may be reduced in some cases due to dry soil having a higher temperature. There may be acute scarcity of water for irrigation in some places. In some regions again production of crops may decrease due to soil rate due to heavy downpour & washing away of fertile top soil reducing thereby the overall crop land area. In regions of middle & high latitudes such as the plains of U.

S. A, Western Europe, Siberia, the soil will become much drier, soil productivity will decrease. Recently it has been predicted that production of crops in India & pakistan will be reduced by about 30% by 2050. EFFECTS ON OZONE LAYER Ozone layer covers the as a shield in the stratospheric zone of the atmosphere.

It protects all the living being from the harmful effects of UV rays. UV rays is very dangerous as it is able to cause mutation in gene, can also cause skin cancer. it also su press immune system. Green house gases are mainly responsible for ozone layer depletion. CFC is the major ozone destroying gas.

it is commonly called freon's, breakdown the stratosphere & produce chlorine atoms. These chlorine atoms highly effective in destroying ozone layer. Nitrogen oxide is the other green house gas emitted by supersonic jet is found to cause destruction of ozone layer. Nuclear explosions in the atmosphere also produce large quantities of nitrogen oxides which are added to the stratosphere. Carbon tetra chloride, chlorine, fluorine emitted through natural & human activity is also able to decrease a considerable amount of ozone layer.

Recently a large whole has been detected at an altitude of 15 to 20 km above the Antarctic. POSIBLE MEASURES TO COUNTER GREEN HOUSE GASES Emission of the green house gases at increasing rate may be combated mainly through three types of measures: -a) Reducing the emission of green house gases in the atmosphere) prior preparation for adapting with the changing situation in the future, & c) to undertake intensive research on counteractive methodologies. REDUCING THE EMISSION OF GREEN HOUSE GASESThe main constituent among the green house gases is carbon di oxide. for regulating its emission in air in increasing amounts mainly two types of measures have been prescribed viz. reducing the use of fossil fuels & conservation of forests among with development of new forest on large scale. As because combustion of fossil fuel on large quantities is the prime cause of increase in the level of carbon di oxide in air, a reduction of such combustion is urgently necessary.

We will have to think of alternative fuel such as solar energy, hydrogen or atomic energy, hydro-electricity etc. to reduce the emission to a large extent of carbon di oxide in air. The large scale destruction of forest resources must be checked & at the same time all efforts should be made to develop new forests. It has been estimated, however, that about 465 million hectares of new forest are to be develop to absorb the excess a mont of carbon di oxide in air each year.

It is worth r calling in this connection that in an international conference held at Toronto in canada in june, 1988 it was resolved that the industrially developed countries would reduce carbon di oxide emission in air by at least 20 percent by the year 2005. The emission of nitrous oxide may be reduced by regulating the application of nitrogenous fertilizer in agricultural lands in such a way that the loss of nitrogen in the form of gaseous oxides is minimum & also by controlling large scale combustion of fossil fuels. The different oxides of nitrogen, produced during combustion of fossil fuel in the engines of motor vehicles & in various industries, rect with oxygen of air to produce ozone. Therefore for controlling the emission of air in the troposphere it is essential to control the large scale combustion of fossil fuel & to search for alternative fuels. with a view of controlling the production of CFC & halons an international treaty was signed in an conference held in Montreal in Canada in September, 1987 which is known as Montreal protocol. The signatory countries, 49 in number decided that production of CFCs will have to be reduced by 1998 to 50% of the production in 1986.

Later it was realised that merely a reduction of production by 50% is not adequate at all, ha production of such compounds should be totally banned. As such, in London conference held in 1990, it was resolved the production of CFCs must be totally banned by the industrially developed countries by 2000 & by developing countries by 2010. This decision has been made effective since 1992. It is expected that due to such measures the green house effect due to CFCs will be reduced to some extent, although although the danger will not be totally eliminated because of the long term effect of CFCS & halons already emitted in the atmosphere. Most of the ozone destroying CFCs have long life period of the order of 100 years or more. Hence these developed countries should bear the financial responsibility for implementation of programmes to be undertaken for controlling emission of green house gases in the atmosphere.

The third world countries should be generously helped by such developed countries in the programmes of conservation of forests & conservation of newer forests.