Aging and diseased trees emit significant amounts of methane into the atmosphere, a phenomenon that may be contributing to global climate change, a new study says. In samples collected from a forest in northeastern Connecticut, researchers at the Yale School of Forestry & Environmental Studies found that some trees emitted methane — a greenhouse gas 25 times more potent than carbon dioxide — at levels up to 80,000 times greater than ambient air levels. According to their findings, the emissions rate from the forest site may be the equivalent of burning 40 gallons of gasoline per hectare of forest per year, offsetting about 18 percent of the forest’s carbon sequestration capacity. “Because the conditions thought to be driving this process are common throughout the world’s forests, we believe we have found a globally significant new source of this potent greenhouse gas,” said Kristofer Covey, a Yale researcher and lead author of the study, published in the journal Geophysical Research Letters. The researchers found that trees producing methane were commonly older — 80 to 100 years old — and diseased with fungal infections that promote increased methane production.