In order to allow combining of the global warming impact of different greenhouse gases, emission levels are converted into CO2 equivalents. This conversion is based on the ‘Global Warming Potential’ (GWP), i.e. the measure of warming that is contributed by each gas to the greenhouse effect. One kg of CO2 equivalents is equivalent to the effect of one kg of CO2 emission. The emission of 1 kg of nitrous oxide (N2O) equals 298 kg of CO2 equivalents, and the emission of 1 kg of methane (CH4) is equal to 25 kg CO2 equivalents. The GWPs of fluorinated gases vary greatly and levels can be substantial. For example, 1 kg of sulphur hexafluoride (SF6) is equal to 22.8 thousand kg of CO2 equivalents.