A recent study by NOAA (US National Oceanic and Atmospheric Administration) indicates a increase of atmospheric Methane, the likely result of oil and gas drilling boom.
The same NOAA has reported leakages rates at sites in Colorado and Utah at 4 and 9 % respectively. (Nature Journal)
Researchers at Cornel university have suggested leakage rates as high as 7.9%
It is an important issue because methane (CH4) has a Greenhouse gas potential 20 times higher than CO2. If the leakage rate is higher than 3.2% then coal will be a cleaner source!
Natural Gas may be less clean than claimed by industry and some governments. It would be worthwhile to analyze leakage rates in the new gas fields of northern BC, Canada.