The study measured methane emissions at about 20 percent of about 1,200 large, operating landfills in the United States. It adds to a growing body of evidence that landfills are a significant driver of climate change, said Riley Duren, founder of the public-private partnership Carbon Mapper, who took part in the study.

“We’ve largely been in the dark, as a society, about actual emissions from landfills,” said Mr. Duren, a former NASA engineer and scientist. “This study pinpoints the gaps.”