Emissions of carbon dioxide

Carbon dioxide (CO2) makes up the largest share of man-made greenhouse gases. The addition of man-made greenhouse gases to the atmosphere disturbs the earth’s radiative balance (i.e. the balance between the solar energy that the earth absorbs and radiates back into space). This is leading to an increase in the earth’s surface temperature and to related effects on climate, sea level and world agriculture.


Emissions refer to CO2 from burning oil, coal, natural gas and waste materials for energy use. Carbon dioxide also enters the atmosphere from deforestation and from some industrial processes such as cement production. However, emissions of CO2 from these other sources represent a smaller share of global emissions, and are not included. The 2006 IPCC Guidelines for National Greenhouse Gas Inventories provide a fuller, technical definition of how CO2 emissions have been estimated.


These emissions estimates are affected by the quality of the underlying energy data. For example, some countries, both OECD and non-OECD members, have trouble reporting information on bunker fuels and may not be able to accurately split fuel consumption between domestic and international transport. Since emissions from bunkers are excluded from the national totals, this affects the comparability of the estimates across countries. On the other hand, since these estimates have been made using the same method and emission factors for all countries, in general, the comparability across countries is quite good.


Global emissions of carbon dioxide have more than doubled since 1971, increasing on average 2% per year. In 1971, the current OECD countries were responsible for 67% of world CO2 emissions. As a consequence of rapidly rising emissions in the developing world, the OECD contribution to the total fell to 37% in 2013. By far, the largest increase in non-OECD countries occurred in Asia, where China’s emissions of CO2 from fuel combustion have risen, on average, by 6% per annum between 1971 and 2013. Driven primarily by increased use of coal, CO2 emissions from fuel combustion in China increased over tenfold between 1971 and 2013.

Two significant downturns in OECD CO2 emissions occurred following the oil shocks of the mid-1970s and early 1980s. Emissions from the economies in transition declined in the 1990s, helping to offset the OECD increases between 1990 and the present. However, this decline did not stabilise global emissions as emissions in developing countries continued to grow. With the economic crisis in 2008/2009, world CO2 emissions declined by 2% in 2009. However, growth in CO2 emissions have rebounded, with emissions increasing by 1% in 2012 and 2% in 2013.

Disaggregating the emissions estimates shows substantial variations within individual sectors. Between 1971 and 2013, the combined share of electricity and heat generation and transport shifted from one-half to two-thirds of the total. The share of the respective fuels in overall emissions also changed significantly during the period. The share of oil decreased from 48% to 34%, while the share of natural gas increased from 15% to 20% and that of coal in global emissions increased from 38% to 46%. Fuel switching, including the penetration of nuclear, and the increasing use of other non-fossil energy sources only reduced the CO2/total primary energy supply ratio by 6% over the past 40 years.


Further information

Analytical publications

Methodological publications

Table. CO2 emissions from fuel combustion


World CO2 emissions from fuel combustion, by region
Million tonnes