A team of NOAA scientists measuring air quality in a portion of Colorado estimates that 4% of the produced gas at a gas field is leaking into the atmosphere. See http://www.nature.com/news/air-sampling-reveals-high-emissions-from-gas-field-1.9982. That leakage rate is high and would be about 43% greater than current EPA national estimates.
Yet still other data about the leakage rate being developed by the Massachusetts Institute of Technology indicate that the leakage rate is below the current EPA estimate, according to Sergey Paltsev of MIT.
No matter which estimate is right, the leakage rate of methane can be cut and must be cut. Indeed, the EPA proposed July 2011 rules would do the job, even according to Professor Howarth.
Professor Howarth said of the rules in his most recent paper: "Can shale-gas methane emissions be reduced. Clearly yes, and proposed EPA regulations to require capture of gas at the time of well completions are an important step."
The gas industry should for its own good take methane leakage seriously, as nothing more fundamentally risks damaging the brand of gas as a cleaner burning fuel than this issue. Unfortunately, global warming science can lead to major arguments with some in gas industry circles, and not all companies are members of the EPA Gas Star program. As a result, not all are genuinely committed to excellent practices for limiting methane leakage.
Even if the methane leakage rate was 4%, and again MIT thinks it is not, coal would emit substantially more carbon than gas when coal is used for electricity, and nearly all coal is used for that purpose in the USA. But there is no need for the methane leakage rate to be 4%. Cutting methane leakage rates should be something that unites and not divides.