The concentration of methane in the atmosphere has risen sharply—by about 25 teragrams per year — since 2006. In recent years, different research teams have come up with viable but conflicting explanations for the increase.
Some teams have published evidence showing that emissions from biogenic sources is driving the increase. Wetlands, ruminants, and rice paddies—all home to methane-producing microbes—are some of the major sources of biogenic methane.

Other teams have argued that a simultaneous increase in atmospheric ethane, a key component of natural gas, implies that fossil fuels are the culprit. Extracting and transporting fossil fuels add both ethane and methane to the atmosphere via leaks in wells, pipes, and other infrastructure.

Source: What is Behind Rising Levels of Methane in the Atmosphere? : Image of the Day