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Green House Gases (GHG) have different properties which make some considerably more potent as greenhouse gases than others. Therefore, per unit emitted, different gases have differing degrees of impact upon global warming, due to the particular property of the gas (e.g. a longer atmospheric lifetime and/or higher efficiency at retaining and emitting heat within the atmosphere).
Therefore to compare the emissions of different GHGs all emissions are referred to as CO2equivalents (CO2e) (i.e. the amount of CO2 which would have to be released in order to have an equal impact on the atmosphere as the specific amount of another GHG released). This is a scale where CO2 is the reference point and has a global warming potential of 1, every other GHG listed in the Kyoto Protocol (methane, nitrous oxide, sulphur hexafluoride, perfluorocarbons, hydrofluorocarbons) has a greater GWP compared to CO2, see following table for details.
| GHG |
Multiply by the following figure to
obtain the CO2e value: |
| CO2 |
1 |
| CH4 |
23 |
| N2O |
296 |
| SF6 |
22,200 |
| HFCs |
12 - 12,000 |
| PFCs |
5,700 - 11,900 |
(Data source: Third Assessment IPCC report, 2001)
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