It is the phenomenon of Earth’s atmosphere by which the energy of solar radiation, absorbed by the ground and re -emitted as as infra red energy, is prevented from escaping by various gases in the air. These results in a rise in the Earth’s temperature .Without this effect the Earth would be frozen and becomes uninhabitable. However, the increasing levels of so-called green house gases such as carbon dioxide, methane, and chlorofluorocarbons (CFCs)- are enhancing the effect to such an extent that global warming and dramatic climate are becoming more serious. The warming effect of the Earth’s atmosphere is called the greenhouse effect. Radiation from the Sun enters the atmosphere but is prevented from escaping in to space by gases such as carbon dioxide (produced by burning of fossil fuels), nitrogen oxides (from car exhausts) and CFCs (from aerosols and refrigerators). As these gases build up in the atmosphere, the Earth’s average temperature is expected to rise. Fossil fuel consumption and forest fires are the main causes of carbon dioxide build up; methane is a byproduct of agriculture (rice, cattle, sheep etc.).Water vapour is another greenhouse gas. The concentration of carbon dioxide in the atmosphere is estimated to have risen by 25% since the Industrial Revolution ,and 10%since 1950;the rate of increase is now 0.5% a year .Chlorofluorocarbon levels are rising by 5% a year and nitrous oxide levels by 0.4% a year, resulting in a global warming effect of 0.5% since 1900, and a rise of about 0.1°C/ 3°F /year in the temperature of the world’s oceans during the 1980s.Arctic ice was 6-7 m/20-23 ft. thick in 1976 and had reduced to 4-5 m/ 13-17 ft. by 1987.
Greenhouse gases are those atmospheric components that absorb strongly in the infrared region of the spectrum. Infrared radiation is reflected and emitted by the Earth’s surface as heat and causes a fairly large warming effect when trapped by these gases in the atmosphere .
In order of abundance and toxicity as green house gases are water vapour, carbon dioxide Ozone, nitrous oxide, methane, chloroflurocarbons (CFCs).Absorption by water vapour, the most common green house gas explains, explains why many humid or cloudy days feel much hotter than dry, clear days of the same air temperature. Because of these gases, only about 5%of the Earth’s radiation escapes from the atmosphere while more than 90% is radiated back to the surface of the Earth.
It is estimated that by 2030 the average global temperature will have risen by between 0.7 and 2.0°c due to imminent climatic change brought about by the greenhouse effect. This would raise the average levels of the seas due to the world’s oceans expanding as they warm up and possible melting of the edges of the polar ice caps, creating a substantial risk of low lying areas and even entire countries being completely and permentely flooded in many areas .Climate change on this magnitude would also have a dramatic impact on biodiversity in different areas and crops could be damaged by climate change .In the U.K ,wetland and peat land areas as well as many coastal communities are reckoned to be mostly under threat. However predictions about global warming and its possible climate effects are tentative and often conflict with each other.
Hence it is high time that sufficient safety measures are laid down by all concerned to prevent undesirable climatic changes and environmental degradation.