CO2, a compound consisting of one carbon and two oxygen. It is a reactant in photosynthesis and necessary for plant life. Abundant in the atmosphere due to anthropogenic and natural activities. It is a greenhouse gas.
[Journal of Geophysical Research;v96; 7301-7312;1991] [Environmental Science and Technology;v28; 1565-1576;1994]
Source: Atmospheric Chemistry Glossary