Global Warming
The year 2016 has been the hottest year on record since 1880 according to an analysis by NASA scientists. It has set a new record of a high temperature by a big margin. According to National Aeronautics and Space Administration (NASA) of USA, the average global temperature during 1998 was 0.18°C warmer than that of the previous record in 1995. And the average global temperature in 1995 was 15.39°C which broke the previous record of 15.38°C of 1990. It shows a steady rise in the global temperature since 1970s. The ten most hot years in the last 130 years have all been in 1980s and 1990s. And out of these 10, the three hottest years were in 1990s.
This inordinate warmth has begun to hit the earth and the entire living world. It is estimated that average temperature has risen by 0.2°C every decade. The threat of the global warming is real and immense. A lot of imbalance has been created in nature by human activities. Consequently there have been unprecedented and unexpected devastations, storms, etc. in various parts of the world specially in the coastal and low-lying regions.
The sea-levels have been rising throughout the globe all these years causing violent storms and cyclones here and there. For example, a cyclone with winds of 270 km per hour wreaked havoc in Bangladesh in 1991 razing more than a million houses and claiming over 1,40,000 lives. During the 1990s Europe, America, Australia etc. have experienced the worst type of storms, hurricanes and tornadoes. Because of global warming temperatures rise, oceans and seas become warmer, and release more energy in the atmosphere which leads to violent storms and very huge losses in terms of man and material. It is estimated that there has been rise in ocean temperature by 1°C per decade. In the recent decades the amount of carbon dioxide in the atmosphere has increased to 350 ppm (parts per million) from a preindustrial level of 275 ppm. Concentrations of carbon dioxide and methane remaining relatively constant up to the 18th century, have risen sharply since then due to human activities. Concentration of nitrous oxide have increased since the mid-eighteenth century, especially during the recent decades. Before the 1930s there was no trace of chloroflurocarbons (CFCS) in the atmosphere.
The trapping of green house gases in the atmosphere is mainly responsible of these dangerous trends of global warming. They raise the earth's temperature which in turn generates destructive storms, cyclones, droughts, floods, forest fires and such other havocs. Widespread human activities such as burning fossil fuels release carbon dioxide in the atmosphere in a very huge quantity and result in green house effect. Then there is a chain reaction. The polar ice begins to melt, the sea levels begin to rise and there are floods and storms.
There have been drastic changes in the earth's climate and weather patterns because of environmental pollution and emission of green house gases. The green house effect contributes to the warming of the earth and rise in its temperature. The greenhouse effect can be generated in a green house. A greenhouse is a glass-house in which plants etc. are kept and grown. The solar radiation enters the green house through its glass covering and is absorbed by the plants, vegetables, etc. But the long wave infrared radiation can not escape back through the glass into the atmosphere and remains trapped. Consequently the temperature inside the greenhouse rises. The similar effect happens to the earth. The earth's atmosphere allows much of the sun's radiation to warm the earth's surface. The warm earth re-radiates electro-magnetic radiation but some of it is absorbed by gases in its atmosphere and there is global warming and environmental pollution. These gases work as a glass-cover and do not permit the radiation to escape. They have accumulated along with the particulates in the atmosphere all these years because of undesirable and excessive burning of fossil fuels.
The green house gases include carbon dioxide, carbon monoxide, chlorine, methane and nitrous oxide. In recent years the amount of these gases has increased alarmingly as a result of the widespread burning and combustion of fossil fuels. Coal, oil, natural gas etc. are the fossil fuels. It is estimated that about 55 per cent of global warming is because of absorption of solar radiation by carbon dioxide and the remaining 45 per cent mainly by methane absorption and by damage to the ozone layer as a result of the release of chloroflurocarbons (CFCS) in the atmosphere.
The size of the hole in the ozone layer observed over Antarctica in 1998 was the largest ever measured and lasted a month longer than the preceding year. Argentina's National Weather Service found that the area covered by low ozone values, that was continuously longer than 10 million square km for more than 100 days, was greater than the one observed during the 1996 season. It was observed that the average amount of ozone during the months of September-October and November showed a shortfall of 40 per cent compared to average values before 1976. That year is considered the base year for measuring atmospheric ozone. The hole started to appear 15 days before the usual time, lasted 2-3 weeks longer and showed the longest duration of areas that had very low ozone. Ozone is a very minor constituent of the earth's atmosphere but is very effective absorber of biologically active solar ultraviolet radiation. This depletion of ozone layer has increased the radiation of ultraviolet rays on the surface of the earth which is very harmful for all living creatures. It causes skin cancer in human beings.
It is estimated that about a billion tons of pollutants are being released every year into the atmosphere. The blanket of carbon emissions is ever increasing and thickening. It has resulted in over 30 per cent more carbon dioxide in the atmosphere today than 200 years ago. Advanced and highly industrialised countries produce more than half of the world's carbon dioxide emissions.
The highly active yellowish gas nitrogen oxide is emitted in the air when fossil fuel is burnt at high temperatures in motor engines and factories. Deforestation and destruction of vegetation has reduced the amount of absorption of carbon dioxide by plants from the atmosphere. Plants use and absorb carbon dioxide and manufacture carbohydrates. The indiscriminate industrialization and felling of trees for timber, fuel and human habitation have further aggravated the problem of global warming and environmental pollution.
Emission of green house gases in such large quantities cause many kinds of respiratory and skin diseases. They also help in the increase of such diseases as malaria, dengue and cholera. In some regions of the world the effects of global warming are now being felt very acutely in the form of climatic and weather changes, droughts, famines, epidemics, destruction of wildlife, huge forest fires, devastating floods, soil-erosion, acid rains and the turning of the fertile soil into arid land.
Global problems need global co-operation and solutions. The problem of global warming is a worldwide problem and calls for a determined and combined efforts by all the nations of the world. The need of the hour is to reduce the emission of green house gases. Alternative fuels should also be searched and developed besides creating more efficient automobiles. The use of renewable sources of energy should be encouraged and developed on a large scale. Wind power, solar-energy, tidal power, hydroelectricity are some of the well known renewable sources of energy. They are not only clean but also freely available and in abundance in nature. They can be exploited to our great advantage. We need to redefine and redesign our energy needs in order to reduce the global warming.
We need to have greater respect for the earth and its environment. It is high time that the people of the world realise the gravity of problem and make determined and combined efforts to reduce global warming appreciably. It is feared that global warming might drive millions of people from their hearths and homes in the new millennium specially in such low-lying Third World countries as Bangladesh. The imminent melting of ice-caps and rise in sea-levels may threaten islands unless we immediately stop the emission of green house gases in the atmosphere. In view of the possible threat to their very existence a number of island nations have formed their own association called Alliance of Small Island States (AOSIS). Unless some serious and meaningful efforts are made on national and international levels to check the menace of global warming, the future appears bleak and foreboding.
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