Climate Change
Global Emissions
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Global Greenhouse Gas Emissions by Gas
Source: IPCC (2007);
based on global emissions from 2004. Details about the sources included in these estimates can be found in the
Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
.
Global Emissions by Gas
At the global scale, the key greenhouse gases emitted by human activities are:
- Carbon dioxide (CO2) - Fossil fuel use is the primary source of CO2. The way in which people use land is also an important source of CO2, especially when it involves deforestation. Land can also remove CO2 from the atmosphere through reforestation, improvement of soils, and other activities.
- Methane (CH4) - Agricultural activities, waste management, and energy use all contribute to CH4 emissions.
- Nitrous oxide (N2O) - Agricultural activities, such as fertilizer use, are the primary source of N2O emissions.
- Fluorinated gases (F-gases) - Industrial processes, refrigeration, and the use of a variety of consumer products contribute to emissions of F-gases, which include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).
Black carbon (BC) is a solid particle or aerosol, not a gas, but it also contributes to warming of the atmosphere. Learn more about BC and climate change on our Causes of Climate Change page.
Global Greenhouse Gas Emissions by Source
Source: IPCC (2007);
based on global emissions from 2004. Details about the sources included in these estimates can be found in the
Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
.
Global Emissions by Source
Global greenhouse gas emissions can also be broken down by the economic activities that lead to their production. [1]
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Energy Supply (26% of 2004 global greenhouse gas emissions) - The burning of coal, natural gas, and oil for electricity and heat is the largest single source of global greenhouse gas emissions.
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Industry (19% of 2004 global greenhouse gas emissions) - Greenhouse gas emissions from industry primarily involve fossil fuels burned on-site at facilities for energy. This sector also includes emissions from chemical, metallurgical, and mineral transformation processes not associated with energy consumption. (Note: Emissions from electricity use are excluded and are instead covered in the Energy Supply sector.)
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Land Use, Land-Use Change, and Forestry (17% of 2004 global greenhouse gas emissions) - Greenhouse gas emissions from this sector primarily include carbon dioxide (CO2) emissions from deforestation, land clearing for agriculture, and fires or decay of peat soils. This estimate does not include the CO2 that ecosystems remove from the atmosphere. The amount of CO2 that is removed is subject to large uncertainty, although recent estimates indicate that on a global scale, ecosystems on land remove about twice as much CO2 as is lost by deforestation.
[2]
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Agriculture (14% of 2004 GHG emissions) - global greenhouse gas emissions) - Greenhouse gas emissions from agriculture mostly come from the management of agricultural soils, livestock, rice production, and biomass burning.
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Transportation (13% of 2004 global greenhouse gas emissions) - Greenhouse gas emissions from this sector primarily involve fossil fuels burned for road, rail, air, and marine transportation. Almost all (95%) of the world's transportation energy comes from petroleum-based fuels, largely gasoline and diesel.
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Commercial and Residential Buildings (8% of 2004 global greenhouse gas emissions) - Greenhouse gas emissions from this sector arise from on-site energy generation and burning fuels for heat in buildings or cooking in homes. (Note: Emissions from electricity use are excluded and are instead covered in the Energy Supply sector.)
- Waste and Wastewater (3% of 2004 global greenhouse gas emissions) - The largest source of greenhouse gas emissions in this sector is landfill methane (CH4), followed by wastewater methane (CH4) and nitrous oxide (N2O). Incineration of some waste products that were made with fossil fuels, such as plastics and synthetic textiles, also results in minor emissions of CO2.
Note on emissions sector categories.
Trends in Global Emissions
Global Carbon Dioxide (CO2) emissions from fossil-fuels 1990-2008
Source of data: Boden, T.A., G. Marland, and R.J. Andres (2010). Global, Regional, and National Fossil-Fuel CO2 Emissions. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/CDIAC/00001_V2010.
Global carbon emissions from fossil fuels have significantly increased since 1900. Emissions increased by over 16 times between 1900 and 2008 and by about 1.5 times between 1990 and 2008.
2008 Global CO2 Emissions from Fossil Fuel Combustion and some Industrial Processes (million metric tons of CO2)
Source: National CO2 Emissions from Fossil-Fuel Burning, Cement Manufacture, and Gas Flaring: 1751-2008.
Emissions by Country
In 2008, the top carbon dioxide (CO2) emitters were China, the United States, the European Union, India, the Russian Federation, Japan, and Canada. These data include CO2 emissions from fossil fuel combustion, as well as cement manufacturing and gas flaring. Together, these sources represent a large proportion of total global CO2 emissions.
Emissions and sinks related to changes in land use are not included in these estimates. However, changes in land use can be important - global estimates indicate that deforestation can account for 5 billion metric tons of CO2 emissions, or about 16% of emissions from fossil fuel sources. Tropical deforestation in Africa, Asia, and South America are thought to be the largest contributors to emissions from land-use change globally. [3] In areas such as the United States and Europe, changes in land use associated with human activities have the net effect of absorbing CO2, partially offsetting the emissions from deforestation in other regions.
Related Links
EPA resources
Greenhouse Gas Emissions
Sources of Greenhouse Gas Emissions (in the United States)
Other resources
Carbon Dioxide Information Analysis Center
Gapminder World
National Inventory Submissions
World Development Indicators
World Resources Institute's Climate Analysis Indicators Tool (CAIT)
References
1. IPCC (2007). Climate Change 2007: Mitigation of Climate Change
.
Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change B. Metz, O.R. Davidson, P.R. Bosch, R. Dave, L.A. Meyer (eds). Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
2. NRC (2010). Advancing the Science of Climate Change
.
National Research Council. The National Academies Press, Washington, DC, USA.
3. Houghton, R.A. (2008). Carbon Flux to the Atmosphere from Land-Use Changes: 1850-2005. In TRENDS: A Compendium of Data on Global Change. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A.