Photosynthesis is the process that removes carbon dioxide from the Earth's atmosphere. Carbon dioxide is also removed from the atmosphere when it mixes with water and forms carbonic acid, which is the acid that's partially responsible for the weatherization of rocks along and in the sea.
The carbonic acid that is used in sea water releases carbon that sinks into the sea floor. Rocks along the coast are weatherized when carbonic acid releases carbon dioxide back into the atmosphere.
Carbon is one of the elements present in all life forms. Decaying plants and animal waste put carbon into the Earth. This carbon then mixes with oxygen to become carbon dioxide. Plant life takes in the carbon dioxide and mixes it with water to form carbohydrates, which are used as energy. As they break down to feed plants, oxygen is released into the atmosphere.
When humans and animals breathe, oxygen is inhaled from the atmosphere, and carbon dioxide is exhaled. The burning of fossil fuels is another way carbon dioxide gets into the atmosphere. As more trees and forests are cut down, less carbon dioxide is pulled from the atmosphere. This is the basis of the greenhouse effect and global warming. More plant life is needed to remove carbon dioxide from the air to prevent climate change.