Feds: California methane leak largest in US history

Greg Nash

Federal scientists said Thursday that Southern California’s massive natural gas leak was the largest methane release in United States history.

The National Oceanic and Atmospheric Administration (NOAA) said more than 100,000 tons of methane, a powerful greenhouse gas with more than 25 times the warming potential of carbon dioxide, were released during the 112-day event.

The climate change impact from the Aliso Canyon facility is equivalent to more than half a million cars’ annual emissions, according to a study NOAA completed with the University of California Davis and others.

“Our results show how failures of natural gas infrastructure can significantly impact greenhouse gas control efforts,” Tom Ryerson, one of the lead scientists, said in a statement.

Stephen Conley, another scientist, said the initial readings from methane-detecting equipment in November made him think there was a malfunction.

“It became obvious that there wasn't anything wrong with the instruments,” he said. “This was just a huge event.”

The leak at an underground gas storage well was finally plugged earlier this year, but not after spewing out enough gas each day to fill the Rose Bowl. Natural gas is mostly made of methane, but it also contains additives to give it a noxious smell and other volatile compounds.

The researchers said the massive leak will make it very difficult for California to meet its greenhouse gas emissions goals for this and last year.