The Aliso Canyon natural gas well blowout, which lasted for months and sickened scores of nearby residents, has been confirmed as the largest methane leak in history.

According to a peer-reviewed study published Thursday in the journal Science, the nearly four-month leak released roughly 100,000 tons of methane—effectively doubling the methane emissions rate of the entire Los Angeles Basin. Southern California Gas Co. said it stopped the leak earlier this month. State Division of Oil, Gas and Geothermal Resources engineers confirmed the leak was halted last week.

“Aliso Canyon will be, certainly, the biggest single [methane] source of the year,” said co-lead study author Stephen Conley of UC Davis and Scientific Aviation. “It’s definitely a monster.”

Beyond that, he told Inside Climate News, “It’s the biggest leak in U.S. history.”

As the Los Angeles Times reports, “Conley piloted a single-engine plane rigged with methane and ethane sensors through the plume and analyzed it during 13 different research flights between Nov. 7 and Feb. 13, with the last readings taken just two days after the well was temporarily halted.”

The newspaper continues:

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