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Just how much warming does methane cause?

- Thursday, July 09, 2009

Several recent articles published in Australia and internationally have focused on the role of methane in global warming, and in particular the role of methane from ruminant livestock. A recent piece in the New Scientist argues that the Global Warming Potential of methane (methane is allocated a GWP of 21 or 23 by the IPCC) is understated because it has a much higher warming potential (above 70) for the short period (10-12 years) that it stays in the atmosphere, and that there should be a much greater focus on reducing methane emissions instead of carbon dioxide emissions.

The GWP of methane is a contentious issue, with the opinions of scientists widely divided about what is the ‘right’ number. Some point out that accounting for the carbon dioxide sequestered in the pastures consumed by ruminants would reduce the GWP of biologically derived methane compared with fossil methane, but no such distinction occurs in current emission accounting systems.

Leaving that debate aside, rather than bashing the ruminant livestock sector and calling for an urgent conversion to vegetarianism (as several Australian academics have recently) the New Scientist article argues that the focus of efforts to reduce methane emissions should be on regulations to reduce methane emissions from the energy and waste sectors (two thirds of all anthropogenic methane). These emissions are ‘low hanging fruit’ than can easily be reduced by regulation.

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