14 DAY TRIAL // Methane emissions in the United States, and in California, may be up to 5 times higher than what scientists currently believe. The conclusion belongs to a new study conducted by investigators at the US Department of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab).
The researchers, working with colleagues from across the country, determined that methane levels from all sources – landfills, humans, farms, oil and gas installations and so on – are much higher than the current Emissions Database for Global Atmospheric Research (EDGAR) estimates.
Overall, they add, methane emissions may be underestimated by a factor of about 1.5, which means that the exact influence US emissions have on the global climate is understated as well. Additional details of the work are published in two separate papers.
Berkeley Lab scientist Marc Fischer published one of the studies in a recent issue of the Journal of Geophysical Research, in a paper called “A multitower measurement network estimate of California’s methane emissions.”
The other paper, entitled “Anthropogenic emissions of methane in the US,” appears in this week's issue of the journal Proceedings of the National Academy of Science (PNAS). The research is authored by Fischer and colleague Sebastien Biraud, alongside Harvard University professor Steven Wofsy.
The JSG paper shows that California releases 1.3 to 1.8 times more methane than the state's Air Resources Board (CARB) estimates. The PNAS paper found that the continental US, as a whole, releases 1.5 times more methane than the Environmental Protection Agency (EPA) estimates.
“This is the first study to quantify methane emissions at regional scales within the continental United States with enough spatial resolution to significantly criticize the official inventories,” Fischer explains.
“Even if we made emissions from livestock several times higher than inventory estimates would suggest for the southwest, you still don’t get enough to cover what’s actually being observed. That’s why it looks like oil and gas are likely responsible for a large part of the remainder,” he adds,
Fischer is the head of the California Greenhouse Gas Emissions Measurement Project (CALGEM) at Berkeley Lab. His work was supported by the DOE Office of Science, the California Air Resources Board, and the California Energy Commission.