By Matt Owens August 27, 2013
The potent greenhouse gas methane (CH4) is given short shrift in climate science, and that's not even considering the methane hydrate or permafrost thaw issues. In fact, sustained methane levels from microbe-generated methane (microbial methanogenesis) could dwarf an Arctic methane hydrate pulse from the East Siberian Shelf.
Current climate models ignore this issue. They use a set of prescribed greenhouse gas levels to run their simulations, and they generally follow the same standardized prescriptions, the RCP scenarios. These RCP scenarios assume that today's atmospheric methane level rises and falls only as a result of direct human activity. This activity is mostly things like methane-producing farming practices and methane releases from burning fossil-fuels.
But looking at the paleoclimate data for the past 800,000 years (when Earth fluctuated between a climate like today's and a colder one that featured large continental ice sheets) shows that methane is closely tied to carbon dioxide levels and temperature. I believe that it's reasonable this relationship will persist, and that therefore very faulty assumptions of methane levels underlie each of the four standard RCP (representative concentration pathway) scenarios. This is a serious problem because these pathways form the basis for almost all climate science studies and evaluations of potential impacts.