Greenhouse gases
The different greenhouse gases have different impacts on the climate. To make it possible to compare the impacts of the emissions of these gases on the climate, the IPCC provides within its reports a factor for characterizing these gases: the Global Warming Potential (GWP). This GWP is established over a characteristic duration: 20, 50, 100 or 500 years.
The emission of 1g of a gas with a GWP of X is equivalent to the emission of Xg of CO2. We then refer to the kilogram equivalent CO2 (kgCO2e).
The GWPs of the various gases vary from report to report for technical reasons linked to the modeling of climatic change and for physical reasons linked to the correlation between the GWP and the concentration of GHGs already emitted into the atmosphere.
The values displayed in the Base Carbone® are calculated using the GWP at 100 years from the 5th report of the IPCC (the latest). See IPCC site: http://www.ipcc.ch/report/ar5/wg1/.
The GWPs of the main gases are as follows:
| Name of gas | GWP at 100 years | |
|---|---|---|
| 4th report of the IPCC | 5th report of the IPCC | |
| CO2f | 1 | 1 |
| CH4f | 25 | 30 |
| CH4b | 25 | 28 |
| N2O | 298 | 265 |
| SF6 | 22800 | 26100 |
| CO2b | -* | -* |
The integration of CO2b (CO2 of biogenic origin) is a little particular. The general documentation details how this is taken into account. In the Base Carbone®, the CO2b is always counted separately and is not included in the totals.