A chemical compound that is the main component of natural gas. Methane is a relatively potent greenhouse gas with a high global warming potential. The abundance of methane in the Earth’s atmosphere in 1998 was 1745 parts per billion, up from 700 ppb in 1750. Methane can trap about 20 times the heat of carbon dioxide. Global warming has the potential to trigger the release of large amounts of methane and cause Arctic methane release from permafrost.