Burning coal for electricity produces about twice the carbon dioxide as burning natural gas. But some scientists remain concerned about methane emissions that leak from gas-drilling operations, in part because methane is a more potent greenhouse gas than carbon dioxide.
Two years ago, the issue gained much more attention with the publication of a study by Cornell University ecology professor Robert Howarth. That study reported that natural gas could be just as bad -- or worse -- than coal for global warming, especially if the issue is examined based on the short time frame in which scientists believe action is needed to curb global warming.
Since then, some other scientists have harshly criticized Howarth's study. But there's also been a lively debate in scientific journals about his results, and about the many variables used to estimate methane emissions from the shale-gas drilling boom across the country.
In its new report, Climate Central found that published estimates of methane leak rates range from 1 percent to 8 percent, with peer-reviewed measurements for individual drilling regions as high as 17 percent. EPA's recently revised data cut the agency's national estimate from 2.2 percent to 1.5 percent.
"Knowing how much methane is leaking from the natural gas system is essential to determining the potential climate benefits of natural gas use," the Climate Central report said.
The report found that, "A pervasive lack of measurements makes it nearly impossible to know with confidence what the average methane leak rate is for the U.S. as a whole.
"More measurements, more reliable data, and better understanding of industry practices are needed," the report said.
Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.