In ominous sign for global warming, feedback loop may be accelerating methane emissions
https://www.science.org/content/article/ominous-sign-global-warming-feedback-loop-may-be-accelerating-methane-emissions
By Paul Voosen, Science Magazine.
Excerpt: 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. That’s because atmospheric methane has become ever more enriched in carbon-12, the lighter isotope of carbon, reversing what had been a multicentury trend, says Xin Lan, a carbon cycle scientist at the Earth System Research Laboratories (ESRL) of the National Oceanic and Atmospheric Administration. “This is a very significant signal,” she says. It points to microbes as the source because they favor reactions that use light carbon, giving the methane they produce a distinctive light signature. ...Climate change may be setting the pace of the emissions.…