Over the past few decades, atmospheric methane levels have stopped increasing and leveled off. This is significant because methane is a particularly potent greenhouse gas, significantly more so than carbon dioxide. The question is what accounts for this trend, and whether it will continue. An article in the November/December issue of American Scientist discusses the mysterious trend and various potential implications.

This happy development wasn't entirely unanticipated, given that the rate of increase has been slowing for at least a quarter-century. Yet the United Nations Intergovernmental Panel on Climate Change has predicated many of its conclusions on scenarios in which methane concentrations would continue growing for decades to come. Thus the recent stabilization of methane levels is something that some scientists are trying very hard to explain.

If current trends continue, then the emission projections embodied in the IPCC's climate projections are significantly overstating the contribution of atmospheric methane to future warming. (Other analysts have suggested the IPCC has grossly overestimated future contributions from CO2, by overestimating likely future CO2 emission trends as well.) All this makes answering the methane industry of more than mere academic import.