Methane Emissions Greatly Underestimated: US Gas, Oil Production Yields Up To 5 Times More Than Believed
Methane emissions from fossil fuel extraction and oil refineries in the United States are nearly five times higher than previous estimates, Harvard University and seven other institutions including U.S. government agencies maintained in an article published Monday in the Proceedings of the National Academy of Science (PNAS). The environmentalists also asserted that U.S. livestock operations may be emitting twice as much methane as previously thought.
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Methane can linger in the atmosphere for 10 years — not a ton compared to its partner in greenhouse gas crime, carbon dioxide, which sticks around for up to 100 years. However, methane traps about 70 times more heat than carbon dioxide does. Most methane emissions arise from run-of-the-mill individual human activities, but about 40 percent comes from the production of fossil fuels, cattle farming, landfills, and the like. That's what the study looked at, providing, what coauthor Anna M. Michalak called "the most solid and the most detailed estimate to date of total U.S. methane emissions." Dr. Michalak, a faculty member in the Department of Global Ecology at the Carnegie Institution for Science, said total methane emissions in the United States appear to be 1.5 times and 1.7 times higher than the amounts estimated by the U.S. Environmental Protection Agency (EPA) and the international Emissions Database for Global Atmospheric Research (EDGAR), respectively. The difference is in how the different environmental groups collected their data.
The EPA and EDGAR collected most of their data from the ground, while the Harvard group procured its more damning evidence from where the gas actually hovers — in the atmosphere. EPA and EDGAR also had depended more on number-crunching: calculating the amount of methane typically released per cow or per unit of coal or natural gas sold. The National Oceanic and Atmospheric Administration (NOAA) and the U.S. Department of Energy collected measurements of methane and other gases from research flights as well as from the tops of telecommunications towers, some as tall as the Empire State Building. "Because we're taking measurements in the atmosphere, which carry with them a signature of everything that happened upwind, we get a very strong number on what that total should be," said Dr. Michalak.
Dr. Michalak and colleagues drew correlations between their methane sampling and meteorological models of temperatures, winds and air masses; demographic data, records of livestock populations, and electricity; oil refinery, natural gas, power plant, rice and coal production. The results: a high correlation between levels of methane and propane in the south-central region suggested a significant role for fossil fuels there. "Most strikingly, our results are higher by a factor of 2.7 over the south-central United States, which we know is a key region for fossil-fuel extraction and refining," noted lead author Scot M. Miller, a doctoral student in Earth and Planetary Sciences through the Harvard Graduate School of Arts and Sciences, in a press release. "It will be important to resolve that discrepancy in order to fully understand the impact of these industries on methane emissions."
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