- US Regulations to Curb Methane Emissions: Methane (CH4) is the second most abundant greenhouse gas (GHG) after carbon dioxide (CO2), accounting for 14 percent of global emissions. Though CH4 is emitted into the atmosphere in smaller quantities than CO2, its global warming potential (i.e., the ability of the gas to trap heat in the atmosphere) is 25 times greater. As a result, methane emissions currently contribute more than one-third of today’s anthropogenic warming.