The amount of carbon dioxide (CO2) that would cause the same effect as a given amount or mixture of other greenhouse gases. The CO2e is determined by converting the other greenhouse gases into carbon dioxide terms by using global warming potentials (GWP); that is, the tonnes of the other gas is multiplied by its associated GWP. (, , )

The equivalent amount of C02 required to create the same level of global warming as another greenhouse gas (eg 1 tonne of SF6 is equivalent to 23,900 tonnes of CO2 using the DEFRA conversion factor).

The quantity of a given GHG multiplied by its global warming potential. This is the standard unit for comparing the degree of warming which can be caused by emissions of different GHGs.