Combatting climate change is a vexing challenge because greenhouse gases belch from billions of cars, cows, and coal-burners. But sometimes lone offenders rise far above the rest. On 23 October 2015, officials reported an ongoing leak at SS25, a well in a massive underground natural gas storage facility near Los Angeles, California. Researchers collected air samples from daily flights over the region from 7 November 2015 through 13 February, 2 days after the leak was capped. In today’s Science they report that—every hour after the blast—the facility released up to 60 metric tons of methane, the primary component of natural gas and the greenhouse gas with the second biggest overall climate impact. The leak was so massive that it essentially doubled the methane emissions for the entire Los Angeles basin, and had the same climate impact in annual greenhouse gas emissions as 572,000 cars.