An anonymous reader quotes Caltech's announcement about the results of a study funded by NASA and the Department of Energy
During the early 2000s, environmental scientists studying methane emissions noticed something unexpected: the global concentrations of atmospheric methane -- which had increased for decades, driven by methane emissions from fossil fuels and agriculture -- inexplicably leveled off. The methane levels remained stable for a few years, then started rising again in 2007... New modeling by researchers at Caltech and Harvard University suggests that methane emissions might not have increased dramatically in 2007 after all. Instead, the most likely explanation has less to do with methane emissions and more to do with changes in the availability of the hydroxyl radical, which breaks down methane in the atmosphere... If global levels of hydroxyl decrease, global methane concentrations will increase -- even if methane emissions remain constant, the researchers say...
Tracking decadal trends in both methane and hydroxyl, Christian Frankenberg and his colleagues noted that fluctuations in hydroxyl concentrations correlated strongly with fluctuations in methane... "Think of the atmosphere like a kitchen sink with the faucet running," Frankenberg explains. "When the water level inside the sink rises, that can mean that you've opened up the faucet more. Or it can mean that the drain is blocking up. You have to look at both."
So what's changing the level of hydroxl
in the atmosphere? The researchers say they have no idea.