CHARLESTON, W.Va. -- Federal government calculations appear to greatly undercount U.S. emissions of the powerful greenhouse gas methane, according to a significant new study published Monday.
Methane emissions are 50 percent larger than estimated by the federal Environmental Protection Agency, and authors of the new study say their conclusions suggest EPA was wrong when it recently decreased agency methane emissions factors for the natural gas industry.
"What we find is that for many regions of the U.S., and most strikingly the south-central U.S., these emissions are much higher than those in current official inventories," said co-author Anna Michalak, a Stanford University environmental engineer.
Michalak and her colleagues used atmospheric methane observations from across North America in 2007 and 2008 to improve estimates of methane gas emissions from a variety of human sources.
The study found large discrepancies with government estimates in some regions of the United States, particularly in the south-central U.S., where total methane emissions were 2.7 times greater than those reported in most inventories.
Methane emissions from just three states, Texas, Oklahoma and Kansas, account for nearly one-fourth of the nation's discharges, or nearly 4 percent of the total U.S. greenhouse gas budget, the new study said.
The new paper was being published in the prestigious Proceedings of the National Academy of Sciences. Co-authors include researchers from Harvard University, the University of Michigan, the National Oceanic and Atmospheric Administration, and the University of Colorado.
Results of the research will continue a growing debate on all as the Obama administration promotes the use of natural gas -- generally thought to be a cleaner alternative to coal -- as part of a plan to combat potentially devastating impacts of global warming.
The new study found that emissions from oil and gas drilling and processing in the south-central U.S. could account for half of the region's methane emissions, and represent a source almost five times higher than in the most commonly used global emissions databases.
Also, the study found emissions were nearly twice as large as current inventories showed for livestock operations, mostly from animal belching and flatulence, and from manure management.
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.