Methane Update

As we have noted previously, the second most important anthropogenic greenhouse gas (after carbon dioxide, or CO₂), is methane (CH₄), and although its concentration (only about 1.8 ppm) is far less than that of CO₂ (at 390 ppm), it’s a stronger greenhouse gas on a per-molecule basis, and it ends up transformed into CO₂ by atmospheric chemistry processes anyway. Also, more than half the atmospheric CH₄ load is due to changes wrought by mankind. Atmospheric methane concentration had stabilized from about 1999 to 2007, but recently began rising again, as reported in Rigby et al (2008).

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