J. Geophys. Res. 113, D21306 (2008)


Methane emissions from energy production in the United States could be as much as 50 to 100 per cent higher than current estimates suggest. A potent greenhouse gas, methane is generated from the production of fossil fuels — mostly natural gas, as well as from biomass burning, agriculture and as from natural sources such as wetlands.

Ethane, released during the production of fossil fuels, is strongly correlated with methane in the atmosphere and as such can be used as an effective tracer of the greenhouse gas. Xiao Yaping, of Harvard University, and colleagues used a chemical transport model to evaluate a global inventory of ethane, verifying the model simulations with observations taken from surface sites and aircraft missions worldwide. They derived a global ethane inventory of 13 million tons per year. The majority of emissions, some 8 million tons per year, came from fossil fuel production, with 90 per cent emitted in the Northern Hemisphere. The team estimated US ethane emissions at 2.4 million tons per year for the 1990s, four times higher than the official inventory from the US Environmental Protection Agency for the same period.

This, they say, suggests a significant under-estimation of methane emissions from energy production in the US.