CHARLESTON, W.Va. -- A major study out this week has provided valuable new data about the global warming pollution from natural gas production, but still leaves unanswered questions about the climate change impacts of an industry that's booming in West Virginia.University of Texas researchers found slightly lower overall emissions rates for the powerful greenhouse gas methane than previously estimated by the U.S. Environmental Protection Agency and other scientific studies.Working with industry and the Environmental Defense Fund, the researchers measured actual emissions from parts of the natural-gas production process at 190 sites around the country.Their much-anticipated results were published Monday in the prestigious Proceedings of the National Academy of Sciences.The findings will be closely scrutinized by policymakers and by all sides of the issue, as the Obama administration hopes increased use of natural gas - generally thought to be a clean alternative to coal - as part of a plan to combat potentially devastating impacts of climate change."This study tackles one of the most hotly debated issues in environmental science and policy today," said Mark Brownstein, associate vice president and chief counsel at EDF's climate and energy program. "It shows that when producers use practices to capture or control emissions ... methane can be dramatically reduced."The research team, led by UT chemical engineer David Allen, found much lower than previously estimated methane emissions from well-completion flowbacks, when liquids used in the process are cleared from the wells.Allen said those results shows that emerging regulatory requirements and improved industry operating practices are making a difference in driving down methane emissions."The way in which wells are drilled and brought into production has been evolving," Allen said.But the team also found higher emissions from some pneumatic pumps used for controlling mechanical devices at well sites and from other equipment leaks, areas that the authors said warrant more attention by scientists and the industry.For the specific emissions sources examined, the new study measured 957 gigagrams of methane. That compares to about 1,200 gigagrams estimated in the lasted EPA inventory. But the new study listed sampling and measuring uncertainties of plus or minus 200 gigagrams."The research did reveal some areas where emissions might be higher than expected, but there were also many areas where emissions were significantly lower, and the overall picture is obviously very reassuring," said Steve Everley, spokesman for the industry group EnergyInDepth.In their push for more natural gas, drilling operators are increasingly using a process called hydraulic fracturing, or fracking, which shoots vast amounts of water, sand and chemicals deep underground to break apart rock and release the gas. More frequently, this process also involves drilling down and then turning horizontally to access more gas reserves.In West Virginia, business and political leaders are eager to continue expanding this practice as companies seek to tap into the vast gas reserves contained in the Marcellus Shale, a formation that stretches across 95,000 square miles from Southern New York and into Eastern Ohio.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 a team of Cornell University researchers led by 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 on the short time frame in which scientists believe action is needed to curb global warming.Since then, industry officials have harshly criticized Howarth's study, and there's been a lively debate in scientific journals about his results and about the many variables used to estimate methane emissions from the shale-gas boom across the country.After reviewing Monday's new study, Howarth issued a statement that called the findings "good news" and said, "it suggests that the oil and gas industry - when sufficiently motivated - can produce natural gas with modestly low emissions."Howarth said that the new study's overall methane leakage rate - 0.42 percent of total gas produced - is slightly better than the low-end of the range his team published, which was 0.6 percent to 2.8 percent of total gas produced.But Howarth cautioned that the new study was based only on measurements at sites chosen by the companies that partnered with EDF and UT researchers on the project. Other recent studies that didn't involve industry partners and used different measurement techniques found emissions that were 10- to 20-fold higher than reported in the new paper, Howarth said."When measurements are made at sites the industry chooses and at times the industry allows, emissions are lower than the norm," Howarth said. "They do better when they know they are being carefully watched."Howarth also noted that the UT-EDF paper looked only at "upstream" gas-production emissions, and not at other potential emissions as natural gas is transported to consumers.The new study is part of a larger research effort spearheaded by EDF to measure methane emissions throughout the natural gas supply chain. Results for the studies addressing other parts of the supply chain are planned during the next 12-18 months."This study did not look at methane emissions from processing, transportation, or distribution of natural gas," said Paulina Jarmillo, a Carnegie Mellon University engineer who has studied the industry's emissions. "Work on measuring emissions from those stages is ongoing. We should probably wait for those numbers before saying that this study proves or disproves what others have reported for the life-cycle greenhouse emissions of natural gas."Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.