On Earth, carbon cycle in nature (sometimes called the carbon cycle) consists of a series of exchanges of substance, which causes carbon between the biosphere, atmosphere, hydrosphere and lithosphere. Most of the carbon in the circuit is in gaseous form, mainly carbon dioxide.

Are shown in the figure flows of carbon between the atmosphere and biosphere, hydrosphere and lithosphere.

Between atmosphere and biosphere: plants and animals at night always eliminated by breathing carbon dioxide. During the day plants assimilate carbon from CO2, using sunlight through the process of photosynthesis converts it into organic combinations, releasing oxygen. Capacity to absorb carbon biosphere is still limited.

Between the atmosphere and hydrosphere: CO2 gas is a relatively soluble in water and there is a balance of CO2 concentration in water. The oceans contain large amounts of dissolved CO2, which, in the event that the balance would be disrupted, could be released into the atmosphere, leading to extreme weather disturbance. Gas solubility in water decreases as temperature increases due to heating of the oceans release CO2 into the atmosphere is a real danger.

Between the biosphere and lithosphere: in the distant past, particularly coal, much of the flora of the time the plants reached the ground, storing carbon in their bodies in the lithosphere in the form of coal deposits. In fact, it is considered that the time Earth’s atmosphere contained oxygen instead of CO2 and plants terraforming atmosphere, oxygen and no carbon dioxide now (current concentration of only 0.03%) is actually the result of this activity.

Between atmosphere and lithosphere: current carbon is released from the lithosphere into the atmosphere as CO2 by human activities (fossil fuel). It is considered that the last half century have been emitted into the atmosphere large amounts of CO2 and methane, which, by the greenhouse effect have led to the beginning of global warming.