Carbon dioxide (CO₂) is a major greenhouse gas, and its level in the atmosphere has been increased by human activities. This increase should bring about global warming. Anthropogenically produced atmospheric carbon dioxide becomes involved in the global carbon cycle and may be stored in the oceans, soil, and living things. The fluxes between the atmosphere and various reservoirs are poorly known but must be understood in order to predict future rises in atmospheric carbon dioxide and global warming. There are also a number of other greenhouse gases whose effect on global warming is nearly comparable to that of carbon dioxide.