Carbon dioxide (CO2) makes up the largest share of "greenhouse gases". The addition of man-made greenhouse gases to the Atmosphere disturbs the earth's radiative balance. This is leading to an increase in the earth's surface temperature and to related effects on climate, sea level rise and world agriculture.
Carbon dioxide (CO2) emissions Definition
The table refers to emissions of CO2 from burning oil, coal and gas for energy use. Carbon dioxide also enters the Atmosphere from burning wood and waste materials and from some industrial processes such as cement production. Emissions of CO2 from these sources are a relatively small part of global emissions and are not included in these statistics. The Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (see below) provide a fuller, technical definition of how CO2 emissions have been estimated for this table. The forecasts provided in the table refer to the Reference Scenario of the World Energy Outlook.
These emissions estimates are affected by the quality of the underlying energy data. For example, some countries, both OECD and non-OECD, have trouble reporting information on bunker fuels and incorrectly define bunkers as fuel used abroad by their own ships and planes. Since emissions from bunkers are excluded from the national totals, this affects the comparability across countries. On the other hand, since the 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 risen by 99%, or on average 2.0% per year, since 1971, and are projected to rise by another 45% by 2030, or by 1.6% per year. In 1971, the current OECD countries were responsible for 66% of the total. As a consequence of rapidly increasing emissions in the developing world, the OECD contribution to the total fell to 46% in 2006, but this is expected to fall to 32% by 2030. By far, the largest increases in non-OECD countries occurred in Asia, where emissions in China have risen by 5.7% per annum between 1971 and 2006. The use of coal in China increased levels of CO2 by 4.8 billion tonnes over the 35-year period.
Two significant downturns can be seen in OECD CO2 emissions, following the oil shocks of the mid-1970s and early 1980s. Emissions from the economies in transition declined over the last decade, helping to offset the OECD increases between 1990 and the present. However, this decline did not stabilise Global emissions as emissions in developing countries grew.
Disaggregating the emissions data shows substantial variations within individual sectors. Between 1971 and 2006, the combined share of electricity and heat generation and transport shifted from one-half to two-thirds of global emissions.
Fossil fuel shares in overall emissions changed slightly during the period. The relative weight of coal in global emissions has remained at approximately 40% since the early 1970s. The share of natural gas has increased from 15% in 1971 to 19% in 2006. Oil's share decreased from 49% to 39%. Fuel switching and the increasing use of non-fossil energy sources reduced the CO2/total primary energy supply (TPES) ratio by 6% over the past 35 years.
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