Reduced methane growth rate explained by decreased Northern Hemisphere microbial sources

Atmospheric methane (CH4) increased through much of the twentieth century, but this trend gradually weakened until a stable state was temporarily reached around the turn of the millennium, after which levels increased once more. The reasons for the slowdown are incompletely understood, with past work identifying changes in fossil fuel, wetland and agricultural sources and hydroxyl (OH) sinks as important causal factors. Here we show that the late-twentieth-century changes in the CH4 growth rates are best explained by reduced microbial sources in the Northern Hemisphere.