Scientific evidence indicates that due to increased concentration of greenhouse gases in the atmosphere, the climate of the earth is changing; temperature is increasing and the amount and distribution of rainfall is being altered (Houghton et al. 1996 cited in ANRS, 2010). The process of global warming shows no signs of decreasing and is expected to bring about long term changes in weather conditions (FAO, 2008). Scientists have presented evidence and tested models to substantiate that global warming is eminent (Chaudhary and Aryal, 2009). IPCC (2007) in its fourth assessment report revealed that warming of the climate system is unequivocal, as it is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level. IPCC has also concluded that more climate change is on the way resulting from past, current, and future greenhouse gas emissions with its potential adverse impacts on socio-economic development of nations.