The Earth’s atmosphere consists of numerous gases, the combination of which allows life on the planet to exist as it does today. One of these gases is carbon dioxide, which makes up only about 0.04 % of the total atmosphere, yet it serves as the basic building block of life forms on Earth. Carbon in carbon dioxide is taken in by plants and converted to plant tissue through photosynthesis. Plants then act as the base of the food chain for virtually all animals, which convert plant tissue (carbon) into animal tissue (carbon). When either plants or animals die, their decay results in the release of carbon dioxide back into the atmosphere. When animals respire, the oxygen that was taken in is converted to carbon dioxide and breathed back into the air. Thus, plants and animals of all types participate in this carbon cycle.

The presence of carbon dioxide in the atmosphere has another role in our world. It, along with other gases, creates a "greenhouse effect," serving as a barrier against the escape of some of the energy from the sun that strikes the Earth. This barrier helps keep in some of the sun’s warmth, causing the Earth to be about 60 degrees F warmer than it would be if there were no such barrier and allowing life as we know it to exist.

Some plant and animal carbon that remained tied up in coal, oil and natural gas is now being released by our civilization as we use these fossil fuels for energy of all kinds. The destruction of forests, mainly in the tropics, also contributes (about 22 %) to the emission of carbon dioxide by man. Man’s activities have resulted in higher levels of carbon dioxide being released to the atmosphere than would normally occur, thereby increasing the ability of these gases to trap the sun’s heat and perhaps causing the Earth to warm more and/or more quickly than it would without human activities. This has given rise to concern by some over global climate change and possible adverse effects resulting from that change.