This animation of the carbon cycle shows the exchanges of carbon dioxide between the planet’s 4 natural reservoirs (atmosphere, biosphere, lithosphere, hydrosphere). Carbon dioxide is a greenhouse gas. The natural carbon cycle is balanced.
Human activities (industrialization, deforestation, combustion of fossil fuels) alter these exchanges and are at the origin of an excess of waste CO₂ in our atmosphere. Only 50% of these wastes are absorbed by natural carbon wells (biomass and ocean).

Click in a reservoir to enlarge it and find details of exchanges there.