Unexpected levels of human-caused methane could mean trouble

A rise in human-caused methane emissions — a phrase that certainly does not make us giggle — has been masked by a decline in natural methane releases, says a new report in Nature. Atmospheric concentrations of methane, less abundant than carbon dioxide but 20 times greenhouse-gassier, have remained relatively stable since 1999. But data from tracking stations around the world show that the human-caused variety, which decreased during the 1990s (likely thanks to the fall of the Soviet Union), has increased since 1999 (likely thanks to the boom in Asia). The uptick was hidden by a 5 percent decline in methane-producing swampland, caused partly by drought. But scientists fear that the wetter weather predicted over the next three to five years could reactivate some wetlands, adding over 11,000 tons of methane a year to the atmosphere. The research comes too late to include in the latest report from the Intergovernmental Panel on Climate Change, which has reduced its earlier estimate of methane’s impact. That stinks.