The Carbon Cycle


The carbon cycle is how carbon is transferred through the various earth systems. Those systems include the atmosphere, the oceans, plants, animals, and rock formations. Since carbon is the main component of the greenhouse gases carbon dioxide and methane, a knowledge of the carbon cycle can help in understanding the effect of carbon on the present climate and how climate may change in response to varying amounts of carbon-based greenhouse gases in the earth systems.

In addition, carbon is a critically fundamental element in the tissues and other substances that form living organisms. No life, as we know it, can exist without carbon and the multifarious compounds that are possible because of it. Living organisms are key components in the absorption and release of carbon into and out of earth systems. Therefore, a study of the carbon cycle is central in understanding how life and climate are entwined.

The Carbon Subcycles

The carbon cycle actually consists of several different earth system interactions. Each of these interactions involve transitions of carbon atoms from one earth system to another. Some carbon transitions are relatively fast, such as those involving living organisms; some are slower, such as those involving the ocean and atmosphere; some are very slow, involving transitions into and out of sediment and rock formations.

There are three principal subcycles of the overall carbon cycle. Although we list them separately for purposes of simplification, all three of these subcycles are intrinsically entwined, with complex interactions that constitute a single, albeit complex, carbon cycle:

The above listed parts of the carbon cycle are shown in the image below.

(click to enlarge)
Carbon Cycles
Yellow = natural fluxes
Red = human contributions
White = stored carbon
Source: NASA Earth Observatory