Global Warming Potential (GWP)

Figure 1 sketches the impact over time of adding one unit of a greenhouse gas to the atmosphere.

Lifetime of the gas is the primary factor in determining the overall warming effect of the gas. Carbon dioxide, for instance, which has an atmospheric lifetime of about 120 years, continues to contribute to radiative forcing, although with decreasing impact, for many decades. And other species, like some CFCs that have very long lifetimes, may contribute to global warming for many centuries.

We define the "global warming potential" (GWP) as the total impact over time of adding a unit of a greenhouse gas to the atmosphere. It is calculated by multiplying the effect of the instantaneous radiative forcing by the concentration of gas added and integrating over time from 0 to some arbitrary time period, T. Carbon dioxide, for instance, has relatively low radiative forcing but a very high volume of gas annually added to the atmosphere and a long atmospheric lifetime, so it has a very high GWP. The CFCs on the other hand have low concentrations but very high radiative forcing factors and very large lifetimes, so they also have very high GWPs.

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