Line chart showing global fossil CO2 emissions annually from 1993 to 2023 with the 2023 data being a projection. Oil was the greatest source of emissions until 2005 when coal became the greatest source. In 2023, emissions are projected to be 15.4 gigatonnes of CO2 for coal, 12.1 for oil, 7.8 for gas and 1.6 for cement.