Carbon cycle

Carbon circulates through the atmosphere, organisms, oceans, soils, rocks and fossil fuels.

Major processes

Photosynthesis removes atmospheric carbon dioxide and incorporates carbon into organic matter.
Respiration releases carbon dioxide.
Decomposition returns carbon from dead organic matter to the environment.
Combustion of biomass and fossil fuels releases carbon dioxide.
Oceans absorb and release carbon dioxide through air–sea exchange.
Sedimentation and geological processes store carbon over long periods.

Important carbon sinks: Oceans, forests, soils and other ecosystems that absorb or store more carbon than they release over a given period.

Carbon sources: Processes that release carbon to the atmosphere, including fossil-fuel combustion, deforestation and some natural processes.