The ageing pipeline infrastructure of Boston, Massachusetts, is leaking natural gas — mostly methane, a potent greenhouse gas — at more than double the rate of previous estimates.

Atmospheric methane levels had plateaued but have been growing worldwide since 2007, for reasons that are unclear. Kathryn McKain at Harvard University in Cambridge, Massachusetts, and her colleagues monitored methane levels at four locations in Boston for a year. They also used a model of atmospheric processes to determine methane emissions. They found that 60–100% of the emitted methane was from the city's natural-gas system, and that the Boston region is losing about 2.7% of its natural gas: 2–3 times more than other estimates.

Cities that consume natural gas could be a bigger source of atmospheric methane than was previously thought.

Proc. Natl Acad. Sci. USA http://doi.org/zpk (2015)