Soviet collapse might explain mysterious trend in global methane emissions

[NickB79]

http://www.sciencemag.org/news/2016/03/soviet-collapse-might-explain-mysterious-trend-global-methane-emissions

From cow farts to factory emissions, there are a lot of ways to add methane to the atmosphere. Since the Industrial Revolution, the concentration of this potent greenhouse gas has risen rapidly and steadily, climbing from 700 parts per billion (ppb) in 1750 to more than 1800 ppb in 2015. But from 1999 to 2006, that increase temporarily leveled out, mystifying scientists. Now, a new study identifies the likeliest culprit behind the plateau—and singles out what may have kick-started the latest methane jump.

Scientists had a lot of suspects to choose from. Natural sources of methane include wetlands and methane hydrates (methane trapped in ice and buried deep under ocean sediments), whereas human sources range from fossil fuel emissions to the burning of crops and trees to the cow and sheep "emissions" that are a byproduct of large-scale livestock farming. And then there are the sinks—the processes that remove methane. The largest methane sink is the atmosphere itself, where a series of chemical reactions converts the gas into carbon monoxide, carbon dioxide, and water. But which of the processes was to blame for the plateau?

“People were thinking in terms of a temporary suppression of sources,” says Heinrich Schaefer, an atmospheric scientist at New Zealand’s National Institute of Water and Atmospheric Research in Wellington, and the lead author of the new study. “They could point to different things that may have contributed, but none was expected to be permanent.”

To find out what happened, Schaefer and his New Zealand-based team joined forces with researchers from the University of Colorado, Boulder, Institute of Arctic and Alpine Research and Heidelberg University in Germany. To get a global look at methane concentrations before, during, and after the plateau, the team amassed atmospheric methane concentration data from measuring stations from Canada to China to Australia, spanning a period from 1984 through 2015. They also examined previously published methane data from Antarctic ice cores extending back 2000 years to the near present.

[sue4e3]

1. interesting