Methane (CH4) is a gas that is naturally present in the atmosphere and is the main component of the fossil fuel, natural gas. In terms of its overall contribution to human-induced climate change, methane is second only to that of carbon dioxide (CO2). It is a potent greenhouse gas, deemed responsible for 20% of post-industrial global warming.
The International Panel on Climate Change (2001) estimates that 1 tonne of methane has a global warming potential (GWP) equivalent to 23 tonnes of CO2.