While methane emissions are mainly due to agriculture (cattle and certain crops), the energy sector (natural gas leaks) and refuse dumps, the level of CFCs is exclusively attributable to industrial production since CFCs are not produced in nature.
Arvioiden mukaan hiilidioksidi (CO2) muodostaa 50 %, metaani (CH4) 19 % ja klooratut fluorihiilivedyt (CFC) 17 % nykyisin ilmakehässä olevista kasvihuonekaasuista.