The Washington Post says that scientists believe they have identified the cause of an upswing in atmospheric methane - microbial production from warmer fields, wetlands (and also cows' stomachs, apparently.)
How do they know?:
Different sources of methane give off different carbon signatures. Methane produced by microbes — mostly single-celled organisms known as archaea, which live in cow stomachs, wetlands and agricultural fields — tends to be “lighter,” or have fewer C13 atoms. Methane from fossil fuels, on the other hand, is heavier, with more C13 atoms.
As the amount of methane has risen in the atmosphere over the past 15 years, it’s also gotten lighter and lighter. The scientists used a model to analyze those changes and found that only large increases in microbial emissions could explain both the rising methane and its changing weight.
The concern is that it may be a dangerous climate feedback happening all by itself, but they can't say for sure:
Michel says it’s too early to say whether this is the beginning of a vicious cycle. “Are these coming from human-caused changes in freshwater systems, or are they a kind of scary climate feedback?” she said. “I want to be careful about what we can and cannot say with this data.”
Researchers say it doesn’t mean that the world can just keep burning natural gas. If wetlands are releasing methane faster than ever, they argue, there should be an even greater push to curb methane from the sources humans can control, such as cows, agriculture and fossil fuels.
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