| http://www.w3.org/ns/prov#value | - It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state, as a trace gas at a concentration of 0.039% by volume.Carbon dioxide also is a by-product of combustion; is emitted from volcanoes, hot springs, and geysers; and is freed from carbonate rocks by dissolution.As of November 2011, carbon dioxide in the Earth's atmosphere is at a concentration of 390 ppm b
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