e149.
Over 20 years, the global warming potential of methane is 72 times that of carbon dioxide, as given in IPCC (2007), chapter 2, p 212, table 2.14, available at http://tinyurl.com/2n27cn . And a 2009 study further suggests that estimates for the GWP of methane should be raised by one third to take into account the effect of methane in breaking down the airborne sulphate particles, which help to cool atmosphere as they reflect heat. See Mark Henderson, “Methane’s Impact on Global Warming Far Higher than Previously Thought”, The Times, 30 October 2009.