Climate change is a broader term that refers to the long term changes in climate, including average temperature and precipitation. According to (IPCC, 2004), “climate change is the statistically significant variation in either the mean state of the climate or in its variability which may be due to natural processes or external forcing, or to persistent anthropogenic changes in the composition of the atmosphere or in land use”. Due to climate change the average temperature of the earth has increased significantly. Nepal is one of the most vulnerable (4^th countries) in terms of climate change. Globally Nepal emits only 0.025 percent of total greenhouse gas emissions. Climate change has threatened the vital biodiversity, water, energy and food security. It has caused rapid melting of glaciers, formation of new supraglacial lakes, expansion of existing lakes, and disappearing of some small lakes have been notices.
About 2 million people rely on climate sensitive sectors like agriculture and forestry for their livelihood. There is rise in maximum temperature at an annual rate of 0.04-0.06 degree Celsius (MOE, NAPA 2010). High mountains are warming faster (0.08 degree Celsius per year) than lower hills and the plains (0.04 degree Celsius per year. Climate change can be a setback for the overall agricultural system. 34.7% GDP of Nepal is from Agriculture according to (DOA, 2011). Overall crop yield (wheat, maize and rice) would decrease in Nepal by up to 30% by the end of this century (IPCC, 2007). Projections for Nepal suggest a 20% loss of snow and glaciated area with 1-degree Celsius increase in temperature increasing likelihood glacial lake outburst flooding (IPCC, 2007). Tropical wet forest and warm temperate rain forest will disappear, and cool temperate vegetation will turn into warm temperate vegetation. Currently, there is no rain forest in tropical and sub-tropical regions in Nepal but a doubling in Carbon dioxide would see an emergence of rain forest in these regions (IPCC,2007).

Increasing temperatures and flood are likely to yield a spread in pathogen and insect borne diseases and exposure of communities to diseased that they have no experience of or immunity to. Human causalities and migration following extreme weather events is also to be anticipated (IPCC,2007).

Global climatic change can affect agriculture through their direct and indirect effects on the crops, soils, livestock and pests. The increase in temperature can reduce crop duration, increase crop respiration rate, alter photosynthetic partitioning to economic products, affect the survival and distribution of pest populations, hasten nutrient mineralization in soils, decrease fertilizer use efficiencies, increase evapotranspiration rate and so on. Livestock is also highly sensitive to the climate change. Rising temperature increases lignification of the plant tissue and reduces the digestibility reducing meat and milk production. Increased heat stress is another pathway affecting the livestock production.

Thus, the ecosystem changes drastically due to climate change.