The Carbon Cycle

The carbon cycle is a central biospheric cycle. In the graphic below, the arrows show the transfer of carbon between the various reservoirs, represented by boxes. This system is closed -- that is, there are no other inputs or outputs other than the reservoirs that are identified. This is, of course, a broad-scale graphic. It does not begin to touch on the complexity of the entire carbon cycle.

The numbers in the boxes represent the reservoir's contents in units of 10¹² (ten to the power of 12) kilograms (of elemental carbon). The transfer rates, shown next to the arrows, are in units of 10¹² kg of C per year. In this representation, about 150 X 10¹² kg of carbon are transferred throughout the cycle each year. The major carbon species in the troposphere are carbon dioxide (CO₂), methane (CH₄), and carbon monoxide (CO). The concentration of CO₂ and the measurements of its partial pressure are important atmospheric indicators of global temperatures, composition of marine sediments, rates of photosynthesis, and rates of oxidation.

For the computational models we will use, the degree of detail and complexity will vary depending upon what is known about the question of interest. An example model shows a computational solution to the study of the flux of carbon between the atmosphere, a "tree", and its interaction with the soil. In this representations stocks or reservoirs are shown as rectangles, the flows and rates associated with those flows are shown as circles. The red arrows show the direction of those flows.

Here is a simplified computational model of a carbon cycle. The carbon cycle calculator looks at relative amounts of atmospheric, terrestrial, and marine carbon with the inclusion of emission of carbon due to burning of fossil fuels. Change the initial amounts of carbon in each state or the emission rate of carbon by moving the sliderbars.