Carbon dioxide emissions

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Published:  May 17, 2010, 12:00 am

Updated: Dec 28, 2021 9:22 pm

Author: C. Michael Hogan

Topic Editor: Sidney Draggan


Carbon dioxide emissions are those discharged into the atmosphere. including animal respiration, fungal and soil respiration, deforestation, fossil fuel combustion and slash and burn agriculture. Carbon dioxide itself is non-toxic and is beneficial as an essential element requisite for the growth of plants. Respiration is the largest source of CO2 emissions; fossil fuel combustion, while much discussed, is responsible for only about one tenth of the global carbon emissions. While carbon dioxide is a known greenhouse forcing agent, it is among the weakest of the greenhouse gases: weaker than methane, water vapor, nitrous oxide, chlorofluorocarbons, sulfur hexafluoride and nitrogen trifluoride.

Animal Respiration

Respiration, both on land and in the sea, is a key component of the global carbon cycle. On land, an estimated 60 Pg C (60 billion tonnes) is emitted to the atmosphere each year by autotrophic respiration. A similar amount, about 55 Pg C, is emitted as a result of heterotrophic respiration. In the sea, autotrophic respiration is thought to account for about 58 Pg of the dissolved inorganic carbon in surface waters each year, with the contribution of heterotrophic respiration being 34 Pg C. Human respiration alone produces about 30 gigatons per annum as of 2021, an amount similar to annual combustion of fossil fuel.

Fungal and Soil Respiration

Fungal and soil respiration is the largest contributor of carbon dioxide emissions, contributing an annual quantity of about 100 gigatons of CO2 per annum. There are a variety of mechanisms including anaerobic respiration mechanisms that contribute to these emissions. (Bogner et al, 2008)


About 7% of the total CO2 global emissions is due to the deforestation agricultural aspect of food production; another 15% of global CO2 emissions derives from the timber harvest industry, in conversion of timber to wood products. Deforestation emissions amount to approximately 11 gigatons of carbon dioxide per annum, or roughly 22% of the emissions from industrial combustion of fossil fuels.

Industrial Carbon Emissions by Country

Industrial carbon dioxide emissions vary considerably among the world's countries, and currently amount to about 36 gigatons per year. The following presents the significant country variations and time trends. There is considerable difference in per capita carbon dioxide emissions between developed nations and underdeveloped countries. The developed countries include those in Western Europe, Australia, New Zealand, USA, Canada, Iceland, Chile, Argentina, Panama, Bahamas, israel, UAE, Qatar, Bahrain, Kuwait, Singapore, Japan, South Korea. Generally, there is a wide gap in emissions per capita between the developed countries and the rest of the world; that difference is not based upon technological prowess, but more upon income inequality and state of abject poverty of most of the populace; for example, China, India and Russia would be classified in the underdeveloped category, since large fractions of their populations are in deep poverty, and without the means to command substantial energy use.

Without regard for state of development, the following sets forth the countries in rank order of absolute total carbon dioxide emissions in gigatons as of 2019: China, 10.6; USA, 5.2; European Union as a whole, 3.3; India, 2.7; Russia, 1.8; Japan, 1.1; South Korea, Germany, Iran, Saudi Arabia, and Indonesia each .8. China is also the nation of fastest 2020 growth in carbon emissions with an increase of .4 gigatons. Of the developed countries, the three countries with lowest carbon emissions per capita are Germany, South Korea and USA.

Slash and Burn

Slash and burn practises are used chiefly in underdeveloped countries as a method of increasing agricultural productivity; about four gigatons of carbon dioxide per annum are released into the atmosphere, or about six percent of all CO2 emissions.

Electric Grid Risks

A number of governmental entities, notably Germany and California, have placed reduction of carbon emissions at such an extreme priority that they are shutting down base load generation from nuclear and natural gas plants. This has already resulted in avoidable power blackouts and brownouts. As further base load generation is threatened to be cut, such as the Diablo Canyon nuclear plant in California, the likelihood increases of large scale electric grid failures. Future electrical grid planning over the period 2020 to 2050 should plan to utilize nuclear fission, nuclear fusion and natural gas as base load for the electric grid.

See Also


  • Bogner, Jean; Pipatti, Riitta; Hashimoto, Seiji; Diaz, Cristobal; Mareckova, Katarina; Diaz, Luis; Kjeldsen, Peter; Monni, Suvi; Faaij, Andre (2008-02-01). "Mitigation of global greenhouse gas emissions from waste: conclusions and strategies from the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. Working Group III (Mitigation)". Waste Management & Research26 (1): 11–32.
  • "Rates of Deforestation & Reforestation in the U.S." Retrieved 2018-04-11.


C. Michael Hogan (2021) Carbon Dioxide Emissions. Encyclopedia of Earth. National Council for Science and Environment. Washington DC Retrieved from