A large amount of carbon dioxide is released into the atmosphere by human activities, one part of which remains in the atmosphere and the other is taken up by the other carbon reservoirs on the Earth. The oceans are a significant sink of atmospheric carbon dioxide. Because of lack of temporal and spatial variations of observed data, there is some controversy over the exact figure. Research on oceanic carbon cycle often uses models, either one-dimensional box models or three-dimensional circulation models. As some parameters for some physical and biochemical processes of carbon dioxide in the oceans are not clearly known, for example, exchange coefficient of CO2 vertical eddy diffusivity, the role of biological web, etc., the obtained results still have large uncertainties. The interaction of CO2 between the atmosphere and terrestrial ecosystems is not sufficiently known. According to the current data and oceanic carbon cycle model, a missing sink is often attributed to the terrestrial biosphere. The so called CO2 fertilization effect is currenly a major hypothesis. Another possible fate of missing sink is soil.