The present concern is really about an unbalanced greenhouse effect from the accumulation of more of these greenhouse gases

Oct 20 - 26, 2003



Much of the improvement in life styles all over the world over the past century has depended upon the availability of energy sources other than human or animal electricity for instance. Most of these additional energy sources depend ultimately upon the burning of fossil fuels, with the release of carbon dioxide to the atmosphere. About 85 per cent of the world's industrial energy come from the combustion of coal, gas and oil. Nuclear and hydroelectric power makes up most of the rest, with solar cells, windmills and the other sources making up no more than 1 per cent or 2 per cent. The combustion of gasoline emits carbon monoxide, hydrocarbons, acetylene and ethylene. These contributes heavily to urban smog and cause difficulties both within the cities and for hundreds of miles downwind. The amount of carbon dioxide released per person all over the developed countries have increased over the past 50 years. It has been observed that per capita release of carbon dioxide is more than 5 tons per year in industrialized countries like USA versus 0.2 tons per year in India.

The global population has increased from 1.6 billion in 1900 to 6 billion in 1999 and is continuing to rise. The environmental pressure has increased quite substantially and continuous to grow. It has been well assumed that climate change is caused by an alteration of the chemical composition of earth's atmosphere by various activities of humankind. A few per cent of the incoming solar energy arrives as invisible ultraviolet radiation with about half of the rest in the visible and the reminder as infrared radiation also invisible. The cooler an object, the less energy it gives off and the peak wavelengths shift from violet to yellow (the sun) to red and then to infrared. Because the surface temperature of the earth is much cooler than the sun, the energy escaping from the earth is emitted at much longer wavelength (the far infrared). However, some of these wavelengths can be strongly absorbed by atmospheric molecules, which contain three or more atoms, such as carbon dioxide, methane, water vapour, ozone, nitrous oxide and the chloroflurocarbons (CFCs), while all of these except the CFCs are natural components of the atmosphere, most are also released by activities of humankind and their atmospheric concentrations have been steadily increasing. These gases are emitted as a result of fossil fuel combustion and deforestation with a proportion remaining in the atmosphere. For example, carbon dioxide is the end-product from the combustion of coal, gas and oil and methane is released from water covered rice plants and from cows and other animals.



Inorganic gas in particular CO2, N2O and CH4 are responsible for global warming and thus have indirect impact on the environment. The concentration of CO2, CH4 and N2O in air is 0.33%, 0.002% and 0.005%, respectively. The potent sources for CO2 are coal and oil based power plants, automobile exhaust and industrial exhaust of various factories. The sources of CH4 entering into the environment are due to losses from processing of natural gas and from bioactive permutation processes. Nitrous oxide (N2O) enters into environment by nitrate fertilizers, vehicular emission and bioactive bacterial degradation of nodules of peas and beans, etc. If all the planetary infrared escapes into the space, the calculated surface temperature of the earth is 0F. Yet the actual average surface temperature of the earth is about 57F. This 57F difference is the natural greenhouse effect and is explained by the absorption of some outgoing far- infrared radiation by molecules in the natural atmosphere. When the escape route is partially blocked by these gases, the planet warms up to produce enough infrared emissions in the unblocked wavelengths, allowing the escaping energy to equal the incoming solar radiation.

The present concern is really about an unbalanced greenhouse effect from the accumulation of more of these greenhouse gases. The increase in surface temperature is known as "greenhouse heating" or the greenhouse effect and the gases responsible have known as 'greenhouse' gases. One of the more predictable consequences of global warming is sea level rise. There are several ways, in which global warming could be expected to affect rise in sea level, namely the thermal expansion of seawater, increased melting of mountain glaciers and changes in mass of the huge ice sheets of greenland and Antarctica. It has been estimated that by the year 2030, global sea level will be 14-24 cm higher than today. The implied rate of rise is about 4-6mm per annum, which is 2-6 times faster than that over the last one hundred year.

Sea level is also influenced by factors such as land movements, subsidence due to redimentation and groundwater pumping as well as lingering crystal movements. This phenomenon will affect the inundation of coastal lands in the areas of Netherlands, Bangladesh, Pakistan, India, USA (South), China, Egypt, The Maldives due to intrusion of salt water, and salt water intrusion means that some crops may have to be abandoned or alternative varieties cultivated. Drainage may also be impeded as sea level rises resulting in loss of yield of ultimately a change in land use of the agricultural area. To control this, the one of the main lines of defence is the careful management of coastal reefs, mangroves and other natural features, and this should form the key element in national precautions against sea level rise.



The profound effect that weather can have on agricultural crops can be seen on common year to year fluctuations in yields, forests, excess rain, high temperature during ear growth or grain growth, cool temperatures during growing period, drought during grain filling and wet weather at harvest will all affect yields adversely. Thus, a change in climate which alters the frequency, intensity or timing of such events could have a substantial effect on agriculture. Higher temperature reduces the water from the soil surface and transpires water from the plants, which definitely reduces the growth of the crops and ultimately the yields. Because under such conditions plants begin to wilt, causing the stomata close.

CONCLUSION: There is increasing evidence that rising emissions of carbon dioxide, methane, nitrous oxide and other radiatively active gases will lead to an increase in the average surface temperature of the earth. By 2030, the world could be 1- 2C warmer and sea level 14-24 cm higher than today. In addition to changes in global temperature, there will be changes in precipitation. The rate and magnitude of these climatic changes is such that they could have a significant impact on agricultural potential in many parts of the world. Important agricultural regions in coastal lowlands and deltas could be threatened by flooding, erosion and salt itrusion. Small, low-lying island states are particularly at risk.

A United Nations Conference in Rio de Janeiro in 1992 to work out a mechanism for control of greenhouse gas emissions. An agreement was reached in Kyoto in 1997 for such controls on four individual gases plus two genetic gas classes, with carbon dioxide at the top of list (The gases include carbon dioxide, methane, nitrous oxide, sulphur, hexflouride hydroflurocarbos and perflurocarbons). The agreement has not been satisfied by the United States and many other countries.