The methane is a gas that falls in the category of ''greenhouse gases''. It is actually the most effective ''greenhouse gas'', much more effective than the CO2, though it has to be mentioned that that is on the short run. Basically, the methane has a property that enables it to trap the heat into the atmosphere. When the heat is reflected from the surface of the Earth it moves back toward the space, but the methane manages to trap big portion of that heat, resulting in an increased greenhouse effect across the globe.
