The importance of methane in the greenhouse effect is its warming effect. Even though it occurs in lower concentrations than carbon dioxide, it produces 21 times as much warming as CO2. Methane accounts for 20% of the 'enhanced greenhouse effect'.
Methane is generated naturally by bacteria that break down organic matter, it is found in the guts of termites and other animals and in natural gas deposits.
Methane remains in the atmosphere for 11-12 years - less time than most other greenhouse gases.
At present, about two thirds of global methane comes from man-made sources, such as the burning of fossil fuel, the accidental release during drilling for natural gas or from cattle ranching.
Since the Industrial Revolution, the level of Methane in the atmosphere has increased by about two and a half times.
The rise in methane started more recently than the rise in carbon dioxide,
and the process of removal from the atmosphere is difficult to predict.
However, without technological change further increases in concentrations