methane emissions

If carbon dioxide is an oven steadily roasting our planet, methane is a blast from the broiler: a more potent but shorter lived greenhouse gas that’s responsible for roughly one-third of the 1.2°C of warming since preindustrial times. Atmospheric methane levels have risen nearly 7% since 2006, and the past 2 years saw the biggest jumps yet, even though the pandemic slowed oil and gas production, presumably reducing methane leaks. Now, researchers are homing in on the source of the mysterious surge. Two new preprints trace it to microbes in tropical wetlands. Ominously, climate change itself might be fueling the trend by driving increased rain over the regions.

If so, the wetlands emissions could end up being a runaway process beyond human control, although the magnitude of the feedback loop is uncertain. “We will have handed over a bit more control of Earth’s climate to microorganisms,” says Paul Palmer, an atmospheric chemist at the University of Edinburgh and co-author of one of the studies, posted late last month for review at Atmospheric Chemistry and Physics.

Most climate scientists already agreed that the post-2006 methane spike has largely not come from fossil fuel production.

Most researchers think a mix of cattle ranching and landfills in the tropics are the main driver of the post-2006 increase, because they have expanded dramatically alongside populations in the region.

But the sharp acceleration in the past couple of years seemed to require some other source. Studies are now implicating the Sudd in South Sudan, the continent’s largest swamp and a region researchers have been unable to study on the ground because of the long-term conflict in the region.