What are the ways that carbon enters back into the atmosphere?

Oh, a million ways! The biggest is probably burning of coal and other fuels, but decomposition of plants and animals also returns carbon, and old trees often give out more carbon than they take in. So: burning, decomposition, respiration.

Carbon moves from living things to the atmosphere. Each time you exhale, you are releasing carbon dioxide gas (CO 2) into the atmosphere. Animals and plants get rid of carbon dioxide gas through a process called respiration. Carbon moves from fossil fuels to the atmosphere when fuels are burned.