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Emissions of methane, an important greenhouse gas, may not have been brought
under control. Although the rate at which methane concentrations in the
atmosphere are increasing has slowed since 1980, Sigrun Karlsdottir and Ivar
Isaksen of the University of Oslo in Norway say that this is not because
emissions have stabilised. Using a computer model, they have calculated that the
change is due to faster breakdown of methane by other pollutants such as carbon
monoxide and oxides of nitrogen, particularly over Southeast Asia
(Geophysical Research Letters, vol 27, p 93).