Carbon dioxide equivalent defined
In study material each GHG described has a different global warming potential (GWP). The GWP of a given GHG indicates how much energy one unit of the GHG absorbs (i.e., the ability of that gas to trap heat in the atmosphere) compared to one unit of carbon dioxide, generally over a 100-year period.
The larger the GWP, the more that the GHG warms the earth compared to carbon dioxide over the stated time period. For example, PFCs and HFCs often absorb thousands of times more energy than carbon dioxide. The GWP of each GHG is published as a factor and used to translate GHGs, other than carbon dioxide, into carbon dioxide equivalent (C02e) units.
The GHG Protocol considers C02e to be the universal unit of measurement for GHGs since it expresses the GWP of each GHG in terms of the GWP of one unit of carbon dioxide. C02e and individual GHGs are often expressed in metric tons, which is the equivalent of 1,000 kilograms (or approximately 2,204 pounds).
The purpose of this measure is to enable a reporting entity, users and other stakeholders to compare the potency of the overall emissions from a reporting entity, both across entities and over time, even when the composition of the GHG emissions changes.