The carbon cycle is a cycle of which carbon moves through all the different spheres of the Earth. Throughout this book, I'll explain the steps of this cycle and how it works.

So how does the carbon cycle work you ask? It may seem complicated, but it's actually quite simple. It's how carbon cycles through the spheres of the Earth. It is in different forms while it moves through the phases. On the next page, we'll address the different forms.

Carbon moves through the atmosphere, hydrosphere, biosphere, and the geosphere. It's found in air, water, land, and plants. It's a gas used to control the Earth's temperature, a liquid in the ocean as carbonic acid, and is considered a carbohydrate in plants.

Carbon is essential in the atmosphere, as it is the most important gas for controlling Earth’s temperature. Carbon dioxide controls the amount of water vapor in the atmosphere and thus the size of the greenhouse effect. Rising carbon dioxide concentrations are already causing the planet to heat up, but doesn’t happen right away because of the ocean soaking up some of the heat. The more carbon humans release into the air, the more the temperature will rise.

Carbon is found in the form of carbonate rocks buried in the geosphere. It can also be found in decaying animals and animal waste. Things such as fossil fuels, coal, natural gas, and petroleum contain carbon as well. Humans burn these fuels, which contribute to carbon being emitted into the air and eventually move through the cycle.

The hydrosphere is a big part of the carbon cycle, since it is a sink for carbon. It can be found dissolved in ocean water and lakes. It's used by organsims to make shells and marine plants use it for photosynthesis (6CO2 + 6H2O + light energy = C6H12O6 + 6O2). Gases containing carbon move between the ocean’s surface and the atmosphere through a process called diffusion.

Nature absorbs 788 billion tons of carbon every year. Even though some of those emissions are absorbed by the ocean and land plants, half of those remain in our atmosphere. Humans emit carbon by deforestation, wood burning, and combustion of fossil fuels. Whenever humans breathe out, they're releasing carbon dioxide into the air during respiration (C6H12O6 + 6O2 = 6CO2 + 6H2O + ATP). All of these things affect the biosphere in different ways.

Deforestation causes carbon dioxide to not be removed from the air, Wood burning causes carbon to be released into the air, and combustion of fossil fuels causes these harmful fumes to be released into the air. All of these things hurt the biosphere and the things living in it. Additional carbon that isn't needed is placed in the atmosphere and it's very harmful.