The carbon cycle was first described by Antoine Lavoisier and Joseph Priestley, and popularised by Humphry Davy.  The global carbon cycle is now usually divided into the following major reservoirs of carbon (also called carbon pools) interconnected by pathways of exchange:
* Atmosphere
* Terrestrial biosphere
* Ocean, including dissolved inorganic carbon and living and non-living marine biota
* Sediments, including fossil fuels, freshwater systems, and non-living organic material.
* Earth's interior (mantle and crust). These carbon stores interact with the other components through geological processes.
The carbon exchanges between reservoirs occur as the result of various chemical, physical, geological, and biological processes. The ocean contains the largest active pool of carbon near the surface of the Earth.
The natural flows of carbon between the atmosphere, ocean, terrestrial ecosystems, and sediments are fairly balanced; so carbon levels would be roughly stable without human influence.