Proven sources of natural gas are about 175 1012 cubic metres (representing about 105 gigatonnes carbon), but it is estimated that there are also about 900 1012 cubic metres of "unconventional" gas such as shale gas, representing about 540 gigatonnes of carbon.(In the past, quantities of hydrocarbons were greater.. 
Lábẹ́ àwọn ìṣẹ̀lẹ̀ déédé nenù jẹ́ ẹ̀fúùfù onítọ́tọ́ aláìláwòrán, oníleoorun, ó jẹ́ ìdá méjì nínú mẹ́ta ìjẹ́kìkí afẹ́fẹ́.. 