Global warming is the phenomenon of a gradual overall increase in the average temperature of the Earth’s atmosphere due to the accumulation of certain gases. The Earth’s atmosphere is made up of major gases namely, oxygen and nitrogen, and minor constituents such as water vapour and carbon dioxide. These gases play a crucial role in moderating the Earth’s temperature. This is because these gases are relatively transparent to incoming visible light from the sun, but absorb the heat radiation given off by the ground and objects exposed to the sun. As a result they produce a heating of the atmosphere by what is known as the “greenhouse effect”. Without the “greenhouse gases” in the atmosphere and the resulting ‘greenhouse effect’, the Earth’s average surface temperature would be as low as – 20°C.
But what is of concern today is the ever increasing level of carbon dioxide and certain other greenhouse gases in the atmosphere during the past several decades. Estimates suggest that by the middle of the 21st century the Earth may be 2° to 9°C warmer. This warming will result in large-scale inundation of coastal areas as a result of rising sea levels due to the melting of polar ice caps. Widespread climatic changes are also forecast due to this global warming.
