In the thick of a Greenland summer of field work in 2015, Benjamin Hmiel and his team drilled into the massive ice sheet’s frozen innards, periodically hauling up a motorcycle-engine-sized chunk of crystalline ice. The ice held part of the answer to a question that had vexed scientists for years: How much of the methane in the atmosphere, one of the most potent sources of global warming, comes from the oil and gas industry?

Previously, geologic sources like volcanic seeps and gassy mud pots were thought to spit out about 10 percent of the methane that ended up in the atmosphere each year. But new research, published this week in Nature, suggests that natural geologic sources make up a