Methane (pronounced /ˈmɛθeɪn/ or /ˈmiːθeɪn/) is a chemical compound with the chemical formula CH4. It is the simplest alkane, the main component of natural gas, and probably[citation needed] the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel. However, because it is a gas at normal conditions, methane is difficult to transport from its source.
Methane is a relatively potent greenhouse gas. The concentration of methane in the Earth's atmosphere in 1998, expressed as a mole fraction, was 1745 nmol/mol (parts per billion, ppb), up from 700 nmol/mol in 1750. By 2008, however, global methane levels, which had stayed mostly flat since 1998, had risen to 1800 nmol/mol.