2015: The Year Methane Leaked into the Headlines

Thanks to studies quantifying leaks from natural gas production and urban infrastructure, methane's climate impact got worthy scrutiny this year.

Scientists made significant progress in 2015 measuring methane emissions from the natural gas industry, continuing a years-long quest to quantify the industry's contribution to climate change.  What they found adds to a growing body of evidence that methane leaks are sporadic, difficult to predict, and often far larger than existing government estimates.

Many of the studies came from the Environmental Defense Fund's $18 million project.  Launched in 2011, it aims to measure emissions from every sector of the industry, including production, storage, transmission and natural gas vehicles.  The project has drawn praise for its scope, vision and scrupulous methods.  It's also been criticized for accepting industry funding and sometimes relying on collaboration with oil and gas operators to obtain measurements.

Over a 20-year period, methane is 86 times more powerful at warming the planet than carbon dioxide.  Over 100 years, its potency dwindles to 34.

This means that even small methane leaks throughout the system can erase any climate benefit of burning natural gas instead of coal.

The most recent EDF paper, released in December, found methane emissions from Texas' Barnett Shale were 90 percent higher than estimates from the U.S. EPA estimates.  The study marked the end of a massive two-year campaign to gather data through "top-down" and "bottom-up" techniques (collecting data from the air and on the ground, respectively)—two methods that often yield conflicting numbers.

EDF's study found greater agreement between the methods than previous studies, and the authors created a statistical analysis to more accurately predict the presence of "superemitters"—facilities that emit more than the expected volume of methane.  In the Barnett they found that half the emissions at any time came from just 2 percent of the facilities.  The emissions varied over time and by location, which will complicate efforts to find and fix the largest emitters.

Superemitters were also important in a separate EDF study, which found that natural gas storage sites and compressor stations, which pressurize the gas for transport, leak $240 million worth of methane nationwide per year.  In that case, more than 20 percent of the leaks came from 4 percent of the facilities.  The total amount released was close to EPA estimates.

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