Global Warming: Causes and Effects
Global Warming: Causes and Effects
Global Warming: Causes and Effects
The atmosphere transmits shortwave, solar radiation; allow about 50 % of it to pass through unaltered, to heat the earth's surface. The energy absorbed by the earth is radiated back into atmosphere, but such radiation is long- wave infrared. Instead of transmitted through atmosphere, much of it is absorbed by clouds, cause rise in atmospheric temperature. A huge amount of the energy absorbed in the atmosphere is then returned to the earth's surface, causing a rise in earth's surface temperature. This process is similar as the working of green house, allowing sunlight in, but trapping the resultant heat inside- hence termed "green house effect". Carbon dioxide and water vapor heavily absorb infrared radiation, and block a large portion of earth's emitted radiation. Radiation absorbed by Green House Gases (GHGs) is partly reemitted to earth's surface and increase the temperature on earth's surface. This phenomenon is called greenhouse effect. Trapping heat by GHGs like carbon dioxide, methane, chlorofluorocarbons, nitrous oxide, and water vapor is natural, which allows life on earth by keeping atmosphere suitably warm. Anthropogenic pollutants amplify the natural green house effect, and cause global warming. A global temperature increase of 0.5 to 0.7oC since 1860 parallels the rise in atmospheric CO2 and methane levels.
CGHs in Global warming
Of 20 green house gases, after water vapour, the 4 most important are CO2, CH4, chlorofluorocarbons and nitrogen oxides. Without human interference, carbon within fossil fuels like coal, oil and natural gas would have remained unchanged. Since, industrial revolution, dependence on fossil fuels for energy has been considerably increased. Burning of fossil fuels release CO2 into atmosphere. Since 1850, atmospheric CO2 content has increased from 280 parts per million (ppm) to 360 ppm, and is the single greatest cause of this increase. Deforestation also leads to increase in atmospheric CO2 concentration, which is occurring mainly in tropics, where rain forests are rapidly being destroyed. During the past 2 centuries, deforestation, and burning of fossil fuels have released as much excess CO2 as is currently stored in all life forms inhabiting the earth. Atmospheric CO2 has increased about 22% over the past 100 years. If atmospheric CO2 continues to increase at its present rate, its concentration in the atmosphere is predicted to be reached 400 ppm by about 2030. In India, the burning of firewood for cooking still remains to be the major source of CO2.
CH4 is emitted by bacteria inhabiting the guts of cattle, paddy culture, and coal mining. Atmospheric CH4 has doubled over the past years due to human population growth, growth of cattle population, paddy production, garbage dumps, and mining of coal and oil. One third of atmospheric CH4 comes form bogs, swamps and action of termites naturally.
CO is produced by automobiles. Each gallon of petrol produces 3 pound CO, which is emitted through automobile exhaust. CFC's are used as refrigerants, solvents, thermal insulators, foam, and plastic. CFCs have destruction effects on stratospheric ozone layer. CFCs are thousand times as powerful as CO2, and are extremely persistent chemical, and can persist in stratosphere for decades
N2O level increases through agricultural practices, and burning of fossil fuels. Nearly 2/3rds of N20 in atmosphere comes from natural soils and oceans. This is also given out by nitrogen based fertilizers.CO2, CH4, CFC, O3, N20, H20 contributes 50%, 19%, 17%, 8%, 4%, and 2% respectively to global warming.
A global temperature increase of 0.5 to 0.7oC since 1860 parallels the rise in atmospheric CO2 and methane levels. The 1980s were the warmest decade on record; the 11 years between 1987 and 1997 included 9 years of record setting high temperatures. The highest average global temperature was recorded in 1987.
The anticipated changes in global climate are expected to occur at a rate that will probably be too rapid to be tracked by evolutionary processes like natural selection. It is unlikely that all species can simply disperse and move north or south into the newly created climatic regions that will be suitable for them. The resultant changes in floras would have dramatic effects on animals, both on large biogeographic scale and on local community scale. More damaging changes could occur on some isolated islands when migration in a northerly or Southerly direction is not possible, thus causing some species to become extinction. Although average global precipitation may increase, a decrease would be result in some areas especially areas that are already dry. The impact would be least in tropics and most at poles. Greenland, Iceland, Norway, Sweden, Finland, and Siberia will be most affected. Polar icecaps and floating western Antarctica ice sheet would melt. A rise of 50C would raise sea level by 5 metres within a few decades, threatening coastal cities.
It is expected that North America would be warmer and drier. The U.S. would produce decrease amount of grains. North and East Africa, the Middle East, India, West Australia and Mexico would be warmer and wetter and would produce more grains. Rice growing seasons and rise cultivation area could increase. Warmer world would have water crisis in some parts while in other parts it would be wetter than today. More people would be affected by diseases like malaria. Distribution of diseases like Filariasis, Schistosomiasis, and African trypanosomiasis would be reduced. Reduction of CO2 emissions by using fuel- efficient vehicles and public transportation and reforestation to replace trees conserving electricity, solar energy utilization would have significance
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