A new study shows that northern freshwaters are critical emitters of this greenhouse gas. The findings from the Permafrost Carbon Network, an international organization that includes UC Santa Barbara's Sally MacIntyre, also underscore the urgency of combatting human-induced global warming. The results appear in the journal Nature Geoscience.

"Climate-sensitive regions in the north are home to most of the world's lakes," said co-author MacIntyre, a professor in UCSB's Department of Ecology, Evolution, and Marine Biology. "Lakes at high northern latitudes are an important, and often overlooked, source of methane, a potent greenhouse gas."

According to the scientists, climate warming, particularly at high northern latitudes, and longer ice-free seasons in combination with permafrost thaw, are likely to fuel methane release from lakes, potentially causing methane emissions to increase 20 to 50 percent before the end of this century. Such a change, MacIntyre noted, would likely generate a positive feedback on future warming, causing emissions to increase even further.