In order to calculate the combined impact of the different greenhouse gas emissions, emission levels are converted into CO2 equivalents. This conversion is based on the ‘Global Warming Potential’ (GWP); this is the measure of warming that is contributed by each gas to the greenhouse effect. One kg of CO2 equivalents stands for 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 of CO2 equivalents. The GWPs of fluorinated gases vary greatly and levels can be quite substantial. For example, 1 kg of sulfur hexafluoride (SF6) is equal to 22.8 thousand kg of CO2 equivalents.