On the previous page, you observed the yearly fluctuation of carbon dioxide in the atmosphere. This is an example of the way in which atmospheric carbon is involved in the complex biogeochemical cycling of carbon through the biosphere. In many ways, the carbon cycle plays an important role in regulating our planet's climate. Can you think of any other forms of carbon aside from CO2 that could be involved in the carbon cycle?

Open up the Carbon Cycle learning tool and explore the various interconnected sources, sinks and fluxes involved in the carbon cycle. Before you move on, be sure that you can answer the following questions:

• In what ways are the short term, long term and oceanic portions of the carbon cycle interconnected?
• How have humans been changing the balance of the carbon cycle in the past 250 years?
• Both volcanic eruptions (a natural process) and fossil fuel combustion (a human activity) release carbon dioxide from long term storage into the atmosphere. What is the difference between these two fluxes?