Carbon flows between the atmosphere, land, and ocean in a cycle that encompasses nearly all life and sets the thermostat for Earth's climate. By burning fossil fuels, people are changing the carbon cycle with far-reaching consequences.
The carbon cycle describes the process in which carbon atoms continually travel from the atmosphere to the Earth and then back into the atmosphere. Since our planet and its atmosphere form a closed environment, the amount of carbon in this system does not change. Where the carbon is located — in the atmosphere or on Earth — is constantly in flux.