Carbon Cycle

Written By Admin
Dated: March 19, 2007

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The carbon cycle is the cycle in which carbon is exchanged between the hydrosphere, atmosphere, biosphere, and geosphere of the Earth. If this all sounds a bit complex, don’t worry. The carbon cycle is the cycle that takes carbon from the water to the air, the air to the living things like plants and humans, and from the living things back into the Earth (and eventually back into the water to start the cycle anew).

These movements and exchanges occur as the result of carious processes, which range from chemical to biological. Exhaling carbon dioxide is one of these processes in which humans are involved, as well as the release of methane (especially from cow farming). Methane, carbon dioxide, and chlorofluorocarbons are all greenhouse gasses which are released by industrial processes, and which are thought to contribute to global warming.

The carbon is removed from the atmosphere in several ways, one of which is photosynthesis. Plants “breathe in” carbon dioxide, releasing oxygen in the process. It is also absorbed into the ocean near the poles where the cool temperatures make the carbon dioxide more soluble. Organisms in the surface ocean areas produce and shed carbon as well in the forms of shells or other hard body parts. The carbon sinks, creating a downward flow.


Image redrawn from NASA's Earth Observatory.

Life on Earth is known as carbon based, and carbon is as necessary to the life cycle of Earth’s organisms as we are to the carbon cycle. From photosynthesis, which takes in carbon from the air, to the consumption of carbon-rich plants by some living things, to the consumption of these creatures by other organisms, we all get our share of carbon in the biosphere. The burning of biomasses such as forests releases carbon into the atmosphere.

The burning of sediment, however, like coal, will also release a great deal of carbon into the air. The ocean is probably the least well known of the spheres in terms of the carbon cycle. We know that as carbon sinks and becomes sediment, that it forms the basis for future fossil fuels, and that carbon helps to balance the pH levels of the ocean.

So what is carbon? Carbon is the sixth element of the periodic table, and can be found as graphite, or in the form of diamonds. This is most interesting because of the paradox of carbon, which forms both the hardest natural material known to man, as well as one of the softest. Diamonds and graphite, both pure carbon, have such opposite properties that it is often remarked upon.

Carbon is also the fourth most prevalent element in the universe, and is found in all forms of life on Earth. It is part of the DNA and RNA in our bodies (as well as the bodies of all other living organisms on Earth) and is ingested, used, and stored in our bodies in multiple forms.

We already know how carbon combines with oxygen to form carbon dioxide. It can also combine with hydrogen to form hydrocarbons, which are what we call fossil fuels. When combined with oxygen and hydrogen, carbon forms many important biological compounds such as sugars, cellulose, fats, alcohols, chitins, lignans, and aromatic esters. Add nitrogen to carbon to form alkaloids, and add sulfur to that to get amino acids and proteins.

In short, carbon is present in (just about) everything on Earth. If this is the case, then it might seem like the burning of fossil fuels like petrol for our cars should have no affect on the atmosphere at all, and one could conclude that global warming is a myth thought up to scare us. This is far from the truth, however.

In the carbon cycle, there exists a certain balance. There is carbon in the air, water, sediment and in life, and there is a balance or budget that is naturally maintained between the four. In our burning of fossil fuels, however, the release of carbon into the air in its various forms has fast outpaced the natural balance of things, putting more carbon into the air than ever before.

The release of these gasses (carbon dioxide, methane, chlorofluorocarbons) in such great amounts causes them to build up in the atmosphere and trap the heat-energy that the Earth radiates. As the gasses continue to build, we see positive feedback effects such as the melting of Siberian swamps, which will produce additional methane and cause additional warming.

This may sound scary, but there is evidence that we may simply be exacerbating an existing natural cycle, and the facts of global warming are hotly debated. To do what you can now, take public transit or walk whenever you can, and look into efficient appliances. If you monitor your energy output, you will help keep carbon out of the air, and aid in the maintenance of the carbon cycle.