All life on Earth is based on carbon, the sixth element of the periodic table. The term carbon cycle refers to the movement of carbon in various forms between Earth's biogeochemical reservoirs: the oceans, the atmosphere, plants, animals and soils on land (the land biosphere), and the geosphere (rocks). Carbon dioxide (CO₂) in the air traps heat, contributing to warming of Earth's surface (called the greenhouse effect) and thereby influencing the climate. Human activities such as burning fossil fuels and clearing forests are causing the amount of CO₂ in the atmosphere to increase rapidly. Concern that global climate change may result has led to a pressing need for scientific research to better understand the global carbon cycle.

The Path of Carbon

To illustrate some of the important processes of the carbon cycle one can follow a carbon atom as it moves through the biogeochemical reservoirs of...