Plot twist in methane mystery blames chemistry, not emissions, for recent rise | Science News

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Plot twist in methane mystery blames chemistry, not emissions, for recent rise

Falling levels of a molecule that destroys the greenhouse gas may be behind increasing concentrations since 2007

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8:00am, April 20, 2017
March hydroxyl distribution

RADICAL THEORY  Changes in the concentration of a highly reactive compound in the atmosphere called hydroxyl may be to blame for a rise in global methane levels since 2007, new research suggests. Redder regions in this simulation of a typical March hydroxyl distribution contain higher concentrations of the molecule.

A recent upsurge in planet-warming methane may not be caused by increasing emissions, as previously thought, but by methane lingering longer in the atmosphere.

That’s the conclusion of two independent studies that indirectly tracked concentrations of hydroxyl, a highly reactive chemical that rips methane molecules apart. Hydroxyl levels in the atmosphere decreased roughly 7 or 8 percent starting in the early 2000s, the studies estimate.

The two teams propose that the hydroxyl decline slowed the breakdown of atmospheric methane, boosting levels of the greenhouse gas. Concentrations in the atmosphere have crept up since 2007, but during the same period, methane emissions from human activities and natural sources have remained stable or even fallen slightly, both studies suggest. The research groups report their findings online April 17 in Proceedings of the National Academy of Sciences.

“If hydroxyl were to decline long-term, then it would be bad

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