The naturally occurring greenhouse gases allow incoming ultraviolet solar radiation to pass through relatively unimpeded, but partially absorb and re-emit outgoing infrared terrestrial radiation. This natural process raises the earth’s average temperature from -18 °C to +15 °C, and is hence, vital for life on earth.

Due to human activities such as energy generation from fossil fuels and deforestation atmospheric concentrations of greenhouse gases has been increasing beyond their natural levels, resulting in an enhanced greenhouse effect, causing increase in global temperatures, a phenomenon known as global warming. This warming can be amplified through increases in water vapour, or reduced through increases in stratospheric aerosols. The sum of all these potential changes is referred to as climate change.

Measurement records suggest that the world has already warmed by 0.3 to 0.6 °C since 1860 and the last two decades have been the warmest, suggesting that this has been man made.