Metan, som har et 34 gange højere drivhuspotentiale end kuldioxid, dannes blandt andet i maverne på drøvtyggere, f.eks. hos køer.
Carbon dioxide equivalent is related to global warming potential. Indeed, carbon dioxide equivalency is a quantity that describes, for a given mixture and amount of greenhouse gas, the amount of CO2 that would have the same global warming potential, when measured over a specified timescale.
This means that carbon dioxide equivalency is a time-integrated measure of radiative forcing. It measures the impact that a given gas emission will have over 100 hundred years compared to what an emission of the same amount of CO2 will have over the same period. For example, this means that for the gas methane, the higher initial global warming potential of the gas itself is taken into consideration. However, the fact that methane is broken down over time to CO2 and functions as a greenhouse gas in this form is also included.
The carbon dioxide equivalency for a gas is obtained by multiplying the mass and the global warming potential of the gas. For example, the global warming potential for methane over 100 years is 25. This means that emissions of one million tonnes of methane are equivalent to emissions of 25 million tonnes of carbon dioxide.
Carbon dioxide equivalent is, therefore, a practical way to compare different types of emissions when international agreements are to be made and the most important areas of action to mitigate global warming must be identified.