Thus humans appear to have an effect. Methane concentration in the atmosphere has also been increasing. Naturally this occurs due to decay of organic matter, the digestive processes of organisms, and leaks from petroleum reservoirs. Man has contributed through domestication of animals, increased production of rice, and leaks from gas pipelines and gasoline. In order to understand whether or not humans are having an effect on atmospheric carbon concentrations, we must look at how carbon moves through the environment.
Carbon is stored in four main reservoirs.
In the atmosphere as CO 2 gas. From here it exchanges with seawater or water in the atmosphere to return to the oceans, or exchanges with the biosphere by photosynthesis, where it is extracted from the atmosphere by plants. CO 2 returns to the atmosphere by respiration from living organisms, from decay of dead organisms, from weathering of rocks, from leakage of petroleum reservoirs, and from burning of fossil fuels by humans. From here it precipitates to form chemical sedimentary rocks, or is taken up by organisms to enter the biosphere. CO 2 returns to the hydrosphere by dissolution of carbonate minerals in rocks and shells, by respiration of living organisms, by reaction with the atmosphere, and by input from streams and groundwater.