Since the Industrial Revolution, as the world became excessively dependant on fossil fuels for energy, emissions of greenhouse gases (GHGs) have increased dramatically. The concentration of Carbon dioxide in the atmosphere, for instance, has gone up by 31 per cent since 1750. These gases trap heat, thus leading to ‘global warming’. In the 20th century, the earth’s temperature increased by about 0.6oC due to increasing concentration of GHGs in the atmosphere. It is expected to increase by another 1.4-5.8oC by the end of the 21st century.