Climate change is the greatest environmental, social and economic threats for the planet today. The warming of the climate system is unequivocal, as is now evident from observations of increase in global average air and ocean temperatures, widespread melting of snow and ice and rising global mean sea level. The earth's atmosphere is a global, open-access resource that no one owns but everyone depends on. However, emissions from an enormous variety of human activities led to the inevitable degradation. Effective management of the atmosphere involves balancing the incremental benefits of using it as a sink against the incremental costs of the climate change that may gradually result from tons of emissions.

Acting to prevent climate change today would place a burden on people now alive but would probably leave coming generations with a climate more similar to today's. In contrast, not acting might benefit people today and probably yield little more wealth - but it would leave the world with a worse climate for many generations to come. Instead of restricting emissions, current generations could address these concerns by making additional capital investments to benefit future generations, with the intention of offsetting potential future damages from climate change. The climate of a place is the average weather that it experiences over a period of time. The factors that determine the climate at a location are the rainfall, sunshine, wind, humidity, and temperature. Climate system exists on the earth ever since it came into being.

The earth's average surface temperature has risen by 0.76° C since 1850. Most of the warming that has occurred in the last 50 years is likely to have been caused by human activity. Fourth Assessment Report (AR4), published on 2 February 2007, the Intergovernmental Panel on Climate Change (IPCC) projects that, without further action to reduce greenhouse gas emissions, the global average surface temperature is likely to rise by a further 1.8-4.0°C by the end of this century. Even the lower end of this range would take the temperature increase since pre-industrial times above 2°C, the threshold beyond which irreversible and possibly catastrophic changes become far more likely.