–J. Nocera, “How to Extract Gas Responsibly” NYT (Feb 28, 2012)
FACT: In 2010 and 2011, the EPA substantially revised and increased their estimates of methane emissions from natural gas systems. As of the end of 2011, the most recent EPA data indicate leak rates of 2.5% for conventional natural gas and 3.9% for shale gas (details of calculation here) over the full life-cycle. A recent field study of methane emissions from an unconventional gas field in Colorado suggests the EPA estimates may be low.