Methane packs bigger global warming punch
October 30th, 2009Methane’s impact on global temperatures is about a third higher than generally thought. One tonne of methane has about 33 times as much effect on the climate over 100 years as a tonne of carbon dioxide. The rule of thumb has been that methane is about 25 times more potent than CO2.
That’s the conclusion of a new study led by Drew Shindell of the Nasa Goddard Institute for Space Studies in New York. Nasa scientists found previous estimates have not accounted for methane’s interaction with airborne particles called aerosols. Shindell explains:
“What happens is that as you put more methane into the atmosphere, it competes for oxidants such as hydroxyl with sulphur dioxide. More methane means less sulphate, which is reflective and thus has a cooling effect. Calculations of GWP including these gas-aerosol linkages thus substantially increase the value for methane.
The study, “Improved Attribution of Climate Forcing to Emissions“, was published in the journal Science.
Shindell says substantial reductions in methane, carbon monoxide and black carbon could have a very large impact on climate change efforts over the near term. Over the long term, CO2 is most important – and it lasts hundreds of years, whereas methane breaks down much more quickly.
Shindell’s results suggest that global warming forecasts may be too optimistic.