Anthropogenic emissions are more important globally, but all sources matter. As public concern about methane grows, most of the focus is on cutting methane emissions from anthropogenic sources, such as the fossil fuel industry. That’s crucial. But since emissions from natural sources such as wetlands and permafrost comprise 40% of methane emissions, they’re also important. And compared to anthropogenic emissions, they are less susceptible to mitigation. Global warming exacerbates methane emissions from all sources, natural and anthropogenic.
Some scientists argue that at least half of the global increase in methane is from shale gas development, and that fossil fuels are by far the largest driver overall. Others believe that the agricultural sector is the largest source of methane emissions. At the same time, the background rate of “natural” methane emissions from such sources as swamps, lakes, rising sea levels, and melting permafrost, is accelerating due to climate change and other human causes. Warming-induced methane emissions, and the question of how much of the growth in methane emissions is due to human activity, are subjects of active research.