CHARLESTON, W.Va. -- The promise of natural gas as a "cleaner" alternative to coal has always been problematic. Like coal, natural gas is a fossil fuel whose supplies can't be renewed. But because burning it generates half the carbon dioxide of coal, it has been portrayed as a solution to climate change concerns. Unfortunately, producing natural gas releases methane, a greenhouse gas even more potent than carbon dioxide. And now it appears that humans have been generating even more methane than previously calculated.This is serious and troublesome news. Methane emissions are 50 percent larger than estimated by the U.S. Environmental Protection Agency, says a recent report published in the Proceedings of the National Academy of Sciences.Researchers from Stanford University, Harvard University, the University of Michigan, the National Oceanic and Atmospheric Administration, and the University of Colorado used atmospheric methane observations from across North America in 2007 and 2008 to better measure methane emissions from human sources.In the south-central United States, they found total methane emissions were 2.7 times greater than the amount previously calculated. Emissions in Texas, Oklahoma and Kansas alone accounted for nearly one-fourth of the nation's methane discharges, or almost 4 percent of the total U.S. greenhouse gas budget, they found.And where is this methane coming from? Oil and gas drilling and processing could account for half of that region's methane emissions, and almost five times as much as previous calculations show. The new study also found that methane emissions from livestock and manure were twice as much as previously calculated.Meanwhile, West Virginia, like the rest of the country, eagerly counts on benefits from the shale gas boom. The Obama administration promotes natural gas as part of the nation's plan to produce plenty of energy while avoiding the worst potential effects of global warming.But is natural gas really a bridge fuel to a cleaner future?"With methane having both a higher leakage rate and higher global warming potential than previously thought, the notion of methane as a bridge fuel is falling apart," writes Joe Romm, a fellow at American Progress and founding editor of Climate Progress.Without a price on carbon at the source -- to make fossil fuels reflect their true cost -- the irresistible source of "cheap" energy that natural gas provides delays the development of truly clean energy sources.At the very least, West Virginia and the nation should require drilling and processing operations to use the cleanest methods. The difference in emissions from the best-run facilities and everyone else is great.Writing about this study, Romm says, "our understanding of the limitations of natural gas is now fairly complete. Natural gas is not a bridge to a carbon-free or climate-safe future. In fact, absent both a serious price for carbon and very strong, enforceable national regulations on leakage, natural gas is a gangplank."