11 december 2016

Atmospheric levels of methane, a powerful greenhouse gas, are spiking, scientists report

By Chris Mooney, Washington Post, December 11 at 7:00 PM

The best news about climate change that we’ve heard lately is that for three years straight, the world’s energy-related emissions of carbon dioxide, the most important greenhouse gas, have been flat. The gas has continued to accumulate in the atmosphere, but emissions haven’t gone up, even as economies have continued to grow.

But now we learn that there’s a major dose of bad news to accompany that: What’s true for carbon dioxide is not at all true for methane, the second most important greenhouse gas. Atmospheric concentrations of this gas — which causes much sharper short-term warming, but whose effects fade far more quickly than carbon dioxide — are spiking, a team of scientists reports in an analysis published Sunday in the journal Environmental Research Letters.

Methane concentrations in the atmosphere, they report, were rising only at about .5 parts per billion per year in the early 2000s. But in the past two years, they’ve spiked by 12.5 parts per billion in 2014 and 9.9 parts per billion in 2015. With carbon dioxide rising more slowly, that means that a higher fraction of the global warming that we see will be the result of methane, at least in the next decade or so.


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