The largest natural source of carbon dioxide emissions is from the oceans to the atmosphere, this represents about 330 billion tonnes of carbon dioxide. A staggering amount of gas when you consider there is only approx. 720 billion tonnes at any one time in the whole of the atmosphere. Of course this movement is in both directions, so the oceans release carbon dioxide but they also absorb it, in roughly the same quantities.
If you want to see this emission of gas from water at home, just leave a glass of water on a table and air bubbles will soon appear on the side of the glass. Carbon dioxide is amongst the gases that are in these air bubbles.
Annually this process creates about 220 billion tonnes of carbon dioxide emissions. An important natural source of carbon dioxide is plant and animal respiration. Carbon dioxide is a by-product of the chemical reaction that plants and animals use to produce the energy they need for movement and growth.
Annually, soil organisms create about 220 billion tonnes of carbon dioxide emissions. Many organisms that live in the Earth’s soil use respiration to produce energy. Amongst them are decomposers which break down dead organic material.
Annually this process creates about 0.15 to 0.26 billion tonnes of carbon dioxide (tiny compared to the other processes above).