CO2 Equivalent
Definition
CO2 Equivalent is the amount of CO2 that would cause the same integrated radiative forcing (a measure for the strength of Climate Change drivers) over a given time horizon as an emitted amount of another GHG or mixture of GHGs.
It is the universal unit of measurement to indicate the Global Warming Potential (GWP) of each greenhouse gas, expressed in terms of the GWP of one unit of wikipedia:Carbon Dioxide. It is used to evaluate different reenhouse gases against a common basis.[1]
Conversion factors vary based on the underlying assumptions and as the science advances. There are several different sets of GWP values, derived from different ‘Assessment Reports’ published by the Intergovernmental Panel on Climate Change (IPCC). For example, the “4AR” values are taken from the 4th Assessment Report, published in 2007.
| Formula | Name | 5AR | 4AR | 3AR 2 | AR |
|---|---|---|---|---|---|
| CO2 | Carbon Dioxide | 1 | 1 | 1 | 1 |
| CH4 | Methane | 28 | 25 | 23 | 21 |
| N2O | Nitrous Oxide | 265 | 298 | 296 | 310 |
| SF6 | Sulphur hexafluoride | 23.500 | 22.800 | 22.200 | 23.900 |
| CF4 | Carbon tetrafluoride | 6.630 | 7.390 | 5.700 | 6.500 |
| C2F6 | Hexafluoroethane | 11.100 | 12.200 | 11.900 | 9.200 |
| CHF3 | HFC-23 | 12.400 | 14.800 | 12.000 | 11.700 |
| CH2F2 | HFC-32 | 677 | 675 | 550 | 650 |
| CH3F | HFC-41 | 116 | 92 | 97 | 150 |
| C2HF5 | HFC-125 | 3.170 | 3.500 | 3.400 | 2.800 |
| C2H2F4 | HFC-134 | 1.120 | 1.100 | 1.100 | 1.000 |
| CH2FCF3 | HFC-134a | 1.300 | 1.430 | 1.300 | 1.300 |
| C2H3F3 | HFC-143 | 328 | 353 | 330 | 300 |
| C2H4F3 | HFC-143a | 4.800 | 4.470 | 4.300 | 3.800 |
| C2H4F2 | HFC-152a | 138 | 124 | 120 | 140 |
| C3HF7 | HFC-227ea | 3.350 | 3.220 | 3.500 | 2.900 |
| C3H2F6 | HFC-236fa | 8.060 | 9.810 | 9.400 | 6.300 |
| C3H3F5 | HFC-245ca | 716 | 1.030 | 950 | 560 |
| NF3 | Nitrogen trifluoride | 16.100 | 17.200 |
PCAF Recommendation
- As a baseline, PCAF recommends using 100-year Global Warming Potentials without climate-carbon feedback from the most recent IPCC Assessment report. As defined in[2]
Issues and Challenges
- A conversion factor that involves assumptions and/or models should be distinguished from a unit conversion that is simply recasting a measurement to a different representation
