Last week, a study found that drilling activities at a number of natural gas wells in Pennsylvania emit 100 to 1,000 times more methane into the the atmosphere than the Environmental Protection Agency (EPA) had predicted. Which actually might not be as big of a deal as it would appear, according to the New York Times's Andrew Revkin

"Toward a Better Understanding and Quantification of Methane Emissions from Shale Gas Development," ran in the Proceedings of the National Academy of Sciences of the United States last week and concluded that the EPA had significantly underestimated the amount of methane emitted during the natural gas drilling process. According to the authors

We identified a significant regional flux of methane over a large area of shale gas wells in southwestern Pennsylvania in the Marcellus formation and further identified several pads with high methane emissions. These shale gas pads were identified as in the drilling process, a preproduction stage not previously associated with high methane emissions.

To reach their conclusion, researchers used data from a plane that flew over an area with oil well pads in southwestern Pennsylvania over two days in June of 2012 and measured levels of greenhouse gas emissions in the area. The Los Angeles Times explains: 

Researchers flew their plane about a kilometer above a 2,800 square kilometer area in southwestern Pennsylvania that included several active natural gas wells. Over a two-day period in June 2012, they detected 2 grams to 14 grams of methane per second per square kilometer over the entire area. The EPA’s estimate for the area is 2.3 grams to 4.6 grams of methane per second per square kilometer... The researchers determined that the wells leaking the most methane were in the drilling phase, a period that has not been known for high emissions. 

But, according to Revkin, we should still take the study with a grain of salt. He argues that it's dangerous to generalize based on just two days of data, and that that it's more likely that the numbers reflect problems with specific gas wells, rather than drilling in general. He writes: 

Much of the news coverage and commentary [on the study] was greatly oversimplified, implying that airplane measurements taken on two days in 2012 and showing high methane levels over a handful of wells (and nothing unusual over almost all the other wells in the region) pointed to an extraordinary new pollution and climate change risk.

In fact, he continues, the data could be taken as a sign that drilling for natural gas could be an effective way to move away from coal: "The study is consistent with other recent work covered here that shows there are specific and tractable issues that can be addressed, making gas production far less leaky and thus a legitimate successor to coal mining." 

Revkin adds that according to Cornell University geologist Louis Derry, the methane measured may have predated the well drilling. Derry says

Unfortunately, we have no equivalent data on gas concentrations in this area (or just about any other place) from prior to the start of drilling with which to compare.  This would have been particularly valuable in an area with so much coal, where we might expect high fluxes prior to any shale gas drilling.

It should be noted, however, that the EPA does have a tendency to miscalculate, or at least waffle on, important figures. The LA Times noted in their coverage of the study that "the EPA said it was aware that non-government scientists had come to 'different conclusions about the level of methane emissions from the oil and gas sector.'" And the Associated Press has repeatedly called out the EPA for mis-predicting the negative effects of some biofuels. That seems like something they should work on.