Over those 12 years, methane "decays" to CO2 and water vapor, both greenhouse gases in their own right. And before it decays, it has a much stronger warming eff

Over those 12 years, methane "decays" to CO2 and water vapor, both greenhouse gases in their own right. And before it decays, it has a much stronger warming effect than either. So a ton of methane is strictly worse than a ton of CO2 in absolutely every way.