Matter tells the story of Bob Ackley, a former contractor for gas companies who "switched sides" after realizing that the urban leaks he'd been finding for decades weren't being resolved. The leaks, far more common than most urban dwellers likely realize, seep up from the ground thanks in large part to aging infrastructure that can be more than a century old. Minor leaks can brown vegetation, but bigger ones can lead to explosions. In all cases, leaked gas escapes into the atmosphere, where it becomes a major contributor to global warming (ironically, natural gas is often cited as a more environmentally friendly alternative to coal). Read the full piece — which won the American Association for the Advancement of Science's 2013 Kavli Award for online science journalism — on Medium.