"Atmospheric levels of methane, 20 times more powerful than carbon dioxide (CO2) at trapping heat, stayed steady for two decades to 2006 on wider fertilizer use to grow rice or a surge in natural gas demand, according to two separate studies in the journal Nature.

Climate researcher Fuu Ming Kai from the Massachusetts Institute of Technology's Singapore research center said in one study that methane output from rice fields in the Northern Hemisphere dropped during the period as fertilizers replaced manure and because of reduced water use.

In the second study, Murat Aydin at the University of California, Irvine, concluded that a drop in methane emissions from more efficient burning of fossil fuels and a surge in natural gas demand.

The studies aim to solve a puzzle that has confounded climate scientists for years: why did methane levels in the atmosphere, after rising steadily for many years, taper off in the mid-1980s in a dip lasting two decades?"

David Fogarty reports for Reuters August 12, 2011.
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