From:

https://en.wikipedia.org/wiki/Carbon_dioxide_equivalent Carbon dioxide equivalent**Global warming potential**Carbon dioxide equivalency is a quantity that describes, for a given mixture and amount of greenhouse gas, the amount of CO

2 that would have the same global warming potential (GWP), when measured over a specified timescale (typically 100 years). Carbon dioxide equivalency thus reflects the time-integrated radiative forcing of a quantity of emissions or rate of greenhouse gas emission—a flow into the atmosphere—rather than the instantaneous value of the radiative forcing of the stock (concentration) of greenhouse gases in the atmosphere described by CO2e.

The carbon dioxide equivalency for a gas is obtained by multiplying the mass and the GWP of the gas

For example, the GWP for methane over 100 years is 34,[3] and for nitrous oxide, 298. This means that emissions of 1 million tonnes of methane or nitrous oxide are equivalent to emissions of 34 or 298 million tonnes of carbon dioxide, respectively.

**Equivalent carbon dioxide**Equivalent CO2 (CO2e) is the concentration of CO2 that would cause the same level of radiative forcing as a given type and concentration of greenhouse gas. Examples of such greenhouse gases are methane, perfluorocarbons, and nitrous oxide. CO2e is expressed as parts per million by volume, ppmv.

CO2e calculation examples:

The radiative forcing for pure CO2 is approximated by R F = α ln(C/C0) where C is the present concentration, α is a constant, 5.35, and C0 is the pre-industrial concentration, 280 ppm. Hence the value of CO2e for an arbitrary gas mixture with a known radiative forcing is given by C0 exp(R F/ α) in ppmv.

To calculate the radiative forcing for a 1998 gas mixture, IPCC 2001 gives the radiative forcing (relative to 1750) of various gases as: CO2=1.46 (corresponding to a concentration of 365 ppmv), CH4=0.48, N2O=0.15 and other minor gases =0.01 W/m2. The sum of these is 2.10 W/m2. Inserting this to the above formula, we obtain CO2e = 412 ppmv.

To calculate the CO2e of the additional radiative forcing calculated from April 2016's updated data:[5] ∑ RF(GHGs) = 3.3793, thus CO2e = 280 exp(3.3793/5.35) ppmv = 526.6 ppmv.