Methane has approximately 28x the warming effect of CO2 in those 10 years, and ultimately it breaks down... To CO2 and water. So every ton of CH4 is like 28 ton

Methane has approximately 28x the warming effect of CO2 in those 10 years, and ultimately it breaks down... To CO2 and water. So every ton of CH4 is like 28 tons of CO2 in the medium term, and like 1+ tons of CO2 in the long term (since water vapor is also a GHG).