Carbon dioxide in Earth's atmosphere initial carbon dioxide in the atmosphere of the young Earth was produced by volcanic activity, modern volcanic activity releases only 130 to 230 megatonnes of carbon dioxide each year. These natural sources are nearly balanced by natural sinks, physical and biological processes which remove carbon dioxide from the atmosphere. For example, some is directly removed from the atmosphere by land plants for photosynthesis and it is soluble in water forming carbonic acid. There is a large natural flux of into and out of the biosphere and oceans. In the pre-industrial era these fluxes were largely in balance. Currently about 57%
Carbon dioxide closed, prefilled chamber containing , or exposure to a gradually increasing concentration of . In 2013, the American Veterinary Medical Association issued new guidelines for carbon dioxide induction, stating that a displacement rate of 10% to 30% of the gas chamber volume per minute is optimal for the humane euthanization of small rodents. However, there is opposition to the practice of using carbon dioxide for this, on the grounds that it is cruel. Carbon dioxide is also used in several related cleaning and surface preparation techniques. Carbon dioxide in Earth's atmosphere is a trace gas, currently (mid 2018) having a