How much methane leaks during the entire lifecycle of unconventional gas has emerged as a key question in the fracking debate. Natural gas is mostly methane (CH4). And methane is a far more potent greenhouse gas than (CO2), which is released when any hydrocarbon, like natural gas, is burned.

Even without a high-leakage rate for shale gas, we know that “Absent a Serious Price for Global Warming Pollution, Natural Gas Is A Bridge To Nowhere.”

But the leakage rate does matter. A major 2011 study by Tom Wigley of the Center for Atmospheric Research (NCAR) concluded:

The most important result, however, in accord with the above authors, is that, unless leakage rates for new methane can be kept below 2%, substituting gas for coal is not an effective means for reducing the magnitude of future climate change.

via Bombshell Study: High Methane Emissions Measured Over Gas Field “May Offset Climate Benefits of Natural Gas” | ThinkProgress.