Hydraulic fracturing produces some 40 percent more greenhouse gas emissions than conventional natural-gas development, according to a team of Cornell University researchers.

Not surprisingly, their conclusion has drawn fire from the oil and gas industry. Less predictably, another set of researchers from the same university also questions the finding.

The first group of researchers said their work found that greenhouse gases produced by the U.S. natural-gas industry will grow from 17 to 23 percent during the next 20 years as shale gas continues to replace conventional natural gas.

Responding to their critics, they recently defended and reiterated their findings using fresh data from the federal Environmental Protection Agency.

Based on its large contribution of methane, shale gas development results in greater greenhouse gas emissions than either oil or coal, according to the researchers. They believe that shale gas is not suitable as a “bridge fuel” from fossil fuels to renewable energy, an assertion held by advocates of shale gas exploration.

Most dramatically, their study posits that the Earth’s temperature will increase by 1.5 degrees Celsius over the next 18 years