Role of Methane in Global Warming

Although the proportion of CH₄ in the atmosphere is very low compared to CO₂, the relative contribution of CH₄ to global warming is high due to the high radiative forcing contributed by this gas. The global atmospheric concentration of methane reached 1774 ppb in 2005 compared to 1732 ppb in the early 1990s and only 715 ppb in the pre-industrial era (figure). This increase in atmospheric concentration of CH₄ is responsible for radiative forcing of +0.48 ± 0.05 W m^–2 which is second only to that contributed by CO₂ due to CH₄ having approximately 25 times higher global warming potential (GWP)  compared to CO₂. Therefore, reduction in CH₄ emission is more effective and probably an easier strategy than reducing CO2 emission.

Figure: Trend in the increase in atmospheric concentration of CH₄ over the last 10,000 years and since 1750 (inset) with corresponding radiative forcing. Source: IPPC (2007)

P.S. References available on request.