Under normal conditions the temperature at the surface of the Earth is maintained by the energy balance of the sun rays that strike the planet and heat that is radiated back into the space. The layer of this gas prevents the heat from being re-radiated out. This carbon dioxide layer thus functions like the glass panels of a Greenhouse, allowing the sunlight to filter through but preventing the heat from being re-rediated in outer space. This is so called natural greenhouse effect.
But when there is an increase in carbon dioxide concentration as pollutant most heat is absorbed by CO2 layer and water vapour in the atmosphere, which adds to the heat that is already present. The net result is the heating up of the earth's atmosphere. This is called enhanced greenhouse effect. Thus increasing carbon dioxide levels tend to warm the air in the lower layers of atmosphere on a global scale. Nearly 100 years ago the carbon dioxide level was to 75 ppm. Today it is 350 ppm and by the year 2035 and 2040 it is expected to reach 450 ppm. Now imagine the earth's temperature. Carbon dioxide increases the earth temperature by 50% while chlorofluorocarbons are responsible for another 20% increase. There are enough chlorofluorocarbons up there to last 120 years. What will happen if we do not stop CFC release?
The heat trap provided by atmospheric carbon dioxide probably help to create the conditions necessary for the evolution of life and the greening of Earth. Compare to moderately warm planets, Mars with too little carbon dioxide in its atmosphere is frozen cold and Venus with too much is a dry furnace.
The excess of carbon dioxide to some extent is absorbed by the oceans. But with the industrialisation of waste and increased consumption of energy, carbon dioxide was released into the atmosphere at a faster rate than the capacity of oceans to absorb it. Show the concentration of carbon dioxide in atmosphere increased.
According to some, computerized models, doubling the carbon dioxide level will increase the Global mean temperature by 2 degree Celsius. But some others say that this will be less than one-quarter of a degree. There are other gases also which contribute to greenhouse effect. These are Sulphur Dioxide, Nitrogen dioxide and CFC's discharged by the industry and Agriculture. Even a change of two degrees may disrupt the earth heat budget, causing Castrophic consequences.
Some people believe that changes in the earth's mean temperature will be Apparent by 2050 when the temperature would increase by 1.5 to 4.5 degree Celsius. According to one projection, changes will be the least in the tropics and the most at the poles. So, Greenland, Iceland, Norway, Sweden, Finland, Siberia and Alaska will be among the most affected. The polar ice caps would melt. The floating Western Antarctica Ice sheet could begin to melt. Rise of 5°C would raise the sea level by 5 metres within a few decades, threatening all the densely populated coastal cities from Shanghai to San Francisco. It is suggested that North America would be warmer and drier. The United States would produce less grains. On the other hand, North and East Africa, the Middle East, India, West Australia and Mexico would be warmer and enabling them to produce more grain. Rice growing season as well as the area under rice cultivation could increase. However this may not happen as higher surface temperature will increase the evaporation of water, thus reducing grain yield.
According to an estimate, if all the ice on the earth should melt 200 feet of water would be added to surface of all oceans, and low lying coastal cities as Bangkok and Venice would be inundated. Rise in sea level of 50 to 100 cm caused by Ocean warming would flood low lying lands in Bangladesh and West Bengal. Due to greenhouse effect, there may occur more hurricanes and cyclones and early snow melts in mountains causing more floods during monsoon. According to some, within next 25 years or so, there will be a rise in sea level by 1.5 to 3.5 metres and in Bangladesh alone 15 million people will have to move or drown.
The UNEP has appropriately chosen the slogan "Global Warming: Global Warming" to alert the people on World Environment Day, June 5, 1989.
But when there is an increase in carbon dioxide concentration as pollutant most heat is absorbed by CO2 layer and water vapour in the atmosphere, which adds to the heat that is already present. The net result is the heating up of the earth's atmosphere. This is called enhanced greenhouse effect. Thus increasing carbon dioxide levels tend to warm the air in the lower layers of atmosphere on a global scale. Nearly 100 years ago the carbon dioxide level was to 75 ppm. Today it is 350 ppm and by the year 2035 and 2040 it is expected to reach 450 ppm. Now imagine the earth's temperature. Carbon dioxide increases the earth temperature by 50% while chlorofluorocarbons are responsible for another 20% increase. There are enough chlorofluorocarbons up there to last 120 years. What will happen if we do not stop CFC release?
The heat trap provided by atmospheric carbon dioxide probably help to create the conditions necessary for the evolution of life and the greening of Earth. Compare to moderately warm planets, Mars with too little carbon dioxide in its atmosphere is frozen cold and Venus with too much is a dry furnace.
The excess of carbon dioxide to some extent is absorbed by the oceans. But with the industrialisation of waste and increased consumption of energy, carbon dioxide was released into the atmosphere at a faster rate than the capacity of oceans to absorb it. Show the concentration of carbon dioxide in atmosphere increased.
According to some, computerized models, doubling the carbon dioxide level will increase the Global mean temperature by 2 degree Celsius. But some others say that this will be less than one-quarter of a degree. There are other gases also which contribute to greenhouse effect. These are Sulphur Dioxide, Nitrogen dioxide and CFC's discharged by the industry and Agriculture. Even a change of two degrees may disrupt the earth heat budget, causing Castrophic consequences.
Some people believe that changes in the earth's mean temperature will be Apparent by 2050 when the temperature would increase by 1.5 to 4.5 degree Celsius. According to one projection, changes will be the least in the tropics and the most at the poles. So, Greenland, Iceland, Norway, Sweden, Finland, Siberia and Alaska will be among the most affected. The polar ice caps would melt. The floating Western Antarctica Ice sheet could begin to melt. Rise of 5°C would raise the sea level by 5 metres within a few decades, threatening all the densely populated coastal cities from Shanghai to San Francisco. It is suggested that North America would be warmer and drier. The United States would produce less grains. On the other hand, North and East Africa, the Middle East, India, West Australia and Mexico would be warmer and enabling them to produce more grain. Rice growing season as well as the area under rice cultivation could increase. However this may not happen as higher surface temperature will increase the evaporation of water, thus reducing grain yield.
According to an estimate, if all the ice on the earth should melt 200 feet of water would be added to surface of all oceans, and low lying coastal cities as Bangkok and Venice would be inundated. Rise in sea level of 50 to 100 cm caused by Ocean warming would flood low lying lands in Bangladesh and West Bengal. Due to greenhouse effect, there may occur more hurricanes and cyclones and early snow melts in mountains causing more floods during monsoon. According to some, within next 25 years or so, there will be a rise in sea level by 1.5 to 3.5 metres and in Bangladesh alone 15 million people will have to move or drown.
The UNEP has appropriately chosen the slogan "Global Warming: Global Warming" to alert the people on World Environment Day, June 5, 1989.
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