The Earth's Carbon Budget (Introduction)

　Global climate change is also the history of the carbon budget. In the early days of the Earth's formation, carbon dioxide in the atmosphere (secondary atmosphere) made up 97% of the atmospheric composition and the partial pressure of carbon dioxide reached 40 atmospheres. (Before the stable existence of the oceans, the atmosphere would have consisted of water vapor along with much more carbon dioxide.) The present Earth's atmosphere has 380 ppm carbon dioxide at 1 atmospheric pressure, so the amount of carbon dioxide in the past was 10,000 times greater than today. Today, most of the Earth's carbon is fixed in the crust as limestone. The amount of carbon is 10⁷-10⁸ Pg, which is more than 10,000 times the amount of carbon dioxide in the atmosphere (KITANO, 1997). Below is a brief history of the sequestration of atmospheric carbon dioxide in the earth's crust.