Table 4. Overview of the global warming potentials (GWP) of greenhouse gas based on 1990

Parameters	CO2	CH4	N2O	CFC-11	CFC-12	HCFC-22
Atmospheric lifetime (years)	50–100	10	150	65	130	-
Atmospheric concentration (per volume)	ppm	ppm	ppb	ppt	ppt	-
GWP effect1)(for 100 years’ time horizon)	1	27–29.8	273	6,230	12,500	1,960
Changes in radiation forcing (1980–1990, %)	55	15	6	17		7
In pre-industrial times (1750–1800)	280	0.8	288	0	0	-
At a time of 1990	353	1,072	310	280	484	-
Reduction required (%)	> 65	15–20	70–80	70–75	70–80	40–50

1 kg of gas to the warming effect of CO₂.