The gas is emitted from natural sources, like livestock and wetlands.

A cow grazes in a pasture in Sycamore, a small community in Greene County, PA.

It is also emitted from human activities, such as gas and petroleum systems, landfills, and coal mines.

The Joseph J. Brunner Landfill in Butler County, PA.

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Although it is always around us, methane’s invisibility keeps us oblivious to its presence.

A natural gas pipeline marker in southwestern PA.

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This is particularly troubling because methane is a greenhouse gas that is a significant contributor to global warming — more than 28 times as potent as carbon dioxide at trapping heat in the atmosphere.

Coal storage silos for the Central Processing Plant in Greene County, PA.

Human activities currently account for the majority of emissions, and cutting methane pollution would be the single fastest way to slow the rate of global warming.

MarkWest's Majorsville Gas Plant in Alley Grove, West Virginia, just across the border from Greene County, PA.

© Julian Giordano

Center for History and Economics, 1730 Cambridge Street, S-422, Harvard University, Cambridge, MA 02138