Following are the methods of carbon replenishment of the atmosphere:

(i) Combustion, either natural or human-induced, releases carbon in the atmosphere from peat, coal and oil.

(ii) Photosynthesis is the process by which plants make their food. They release carbon in the form of carbon dioxide in the atmosphere.

(iii) Respiration by consumers and producers return carbon to the environment in the form of carbon dioxide.

(iv) Burning of fossil fuels releases carbon in the atmosphere in the form of carbon monoxide.

(v) Decomposition of organic matter by anaerobic bacteria produces methane that contains carbon.