Science / Medicine : Methane Emissions Recalculated

Scientists may have overestimated by about 25% in calculating worldwide emissions of methane, a gas that promotes global warming, a new study said. That means that efforts to reduce atmospheric buildup of methane by attacking such sources as natural gas leaks may have more effect than previously thought, said A. R. Ravishankara of the National Oceanic and Atmospheric Administration in Boulder, Colo.

The estimate of worldwide methane emission is calculated from measurements of atmospheric concentrations of methane and its rate of removal from the atmosphere, the scientists said. The new study, published in Nature, suggests that estimates of global emissions must be reduced to fit the observed concentrations, they said.

Methane contributes to global warming because it helps the atmosphere trap energy radiating from Earth. Its atmospheric concentration is increasing about 1% a year because of such sources as burning of plant matter and emissions from wetlands, rice fields, landfills, coal mines, oil and gas wells and leaks in natural gas distribution systems.