Carbon pool

This page discusses reservoirs that exchange carbon through output and intake - to learn solely about the intake of carbon, see Carbon sink.

Carbon pools are reservoirs of carbon that have the capacity to both take in and release carbon.[1] There are four very broad global carbon pools which encompass many complex systems which will be discussed on this page. Each of these pools exchange carbon with one another, known as carbon fluxes, comprising what is known as the global carbon cycle.[2]

The amount of carbon in these carbon pools is measured in gigatonnes (GtC): 1 gigatonne, or 1 trillion kilograms of carbon, is equal to the weight of around 200 million elephants! Another interesting way to think about a GtC:

  • Consider the world population (~7.3 billion humans) at an average mass of 60 kg. Assuming an 18% carbon composition of the body,[7] all of the humans on Earth would only make about 0.07 gigatonnes of carbon!

To get an even better visualization of such a large number, click here.

Earth's pools and their carbon content

Earth's crust

Earth's uppermost layer, the crust, makes up the vast majority of carbon and can be looked at in two different categories:[8]

  1. An inorganic reservoir of carbonate rock, estimated to hold 50,000,000 to 100,000,000 GtC (Gigatonnes of Carbon).
  2. A "fossil" reservoir of organic matter which contains the world's fossil fuels - such as coal, oil, and natural gas - which formed over millions of years (see oil formation for more information) and is currently being depleted by humans. The reserves of these fossil fuels contains 1000-2000 GtC. Normally there would be no flux of this carbon into the carbon cycle, however through human actions this carbon is introduced into the other carbon pools unnaturally.

Terrestrial ecosystems

The portion of the Earth with living material creates a reservoir consisting of younger living matter, mostly plants, which includes above-ground matter (450-650 GtC) and below-ground organic matter (1500-2400 GtC). This living matter includes plants, animals, soils and micro-organisms.[2]

Ocean Reservoirs

There are 3 subdivisions of ocean reservoirs:[8]

  1. Living matter, mostly found near the surface, consisting of roughly 3 GtC.
  2. Carbon dissolved throughout the ocean, where the majority of the carbon is, at around 37,000 GtC.
  3. Sedimentary matter, containing mostly carbonates.

Atmospheric Reservoir

The Earth's atmospheric reservoir is kept as a broad category, however it is perhaps the most crucial one. Prior to the Industrial Revolution it contained around 590 GtC; it now contains around 830 GtC.[8] Although this is considerably less than the carbon contained in the ocean and crust, the carbon content in the atmosphere is of critical importance due to its effects on the greenhouse effect and climate.[2] There are various reasons for the drastic increase in atmospheric carbon which is explored in detail here.

See also

To learn about how carbon is exchanged between these different pools visit:

To learn about effects that changes in these cycles bring about, see:


  1. Food and Agriculture Organization of the United Nations. Forests and Climate Change [Online], Available:
  2. 2.0 2.1 2.2 University of New Hampshire GLOBE Carbon Cycle. (Accessed December 29, 2015). Pools, Fluxes and a word about units [Online], Available:
  3. Wikimedia Commons [Online], Available:
  4. Wikimedia Commons [Online], Available:
  5. Wikimedia Commons [Online], Available:
  6. Wikimedia Commons [Online], Available:
  7. LiveScience. The Chemistry of Life: The Human Body [Online], Available:
  8. 8.0 8.1 8.2 M. Melieres and C. Marechal, "Warming in the 20th century," in Climate Change: Past, Present and Future 1st ed., U.K.: Wiley, 2015, ch.29, sec.1, pp. 298-301

Authors and Editors

Jordan Hanania, Kailyn Stenhouse, Jason Donev
Last updated: February 18, 2016
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