registerShift and other readers sent in news that the Arctic Ocean seabed is leaking methane. "...climate experts familiar with the new research reported in Friday's issue of the journal Science that even though it does not suggest imminent climate catastrophe, it is important because of methane's role as a greenhouse gas. Although carbon dioxide is far more abundant and persistent in the atmosphere, ton for ton atmospheric methane traps at least 25 times as much heat. ... [One scientist] estimated that annual methane emissions from the East Siberian Arctic Shelf total about seven teragrams. (A teragram is 1.1 million tons.) By some estimates, global methane emissions total about 500 teragrams a year. ...about 40 percent is natural, including the decomposition of organic materials in wetlands and frozen wetlands like permafrost."