Multiple-century response of a coupled ocean-atmosphere model to an increase of atmospheric carbon dioxide

To speculate on the future change of climate over several centuries, three 500-year integrations of a coupled ocean-atmosphere model were performed. In addition to the standard integration in which the atmospheric concentration of carbon dioxide remains unchanged, two integrations are conducted. In one integration, the CO₂ concentration increases by 1% yr^-1 (compounded) until it reaches four times the initial value at the 140th year and remains unchanged thereafter. In another integration, the CO₂ concentration also increases at the rate of 1% yr^-1 until it reaches twice the initial value at the 70th year and remains unchanged thereafter. During the 500-year period of the doubling and quadrupling experiments, the global mean surface air temperature increases by about 3.5°C and 7°C, respectively. The rise of sea level due to the thermal expansion of sea water is about 1 and 1.8 m, respectively, and could be much larger if the contribution of meltwater from continental ice sheets were included. It is speculated that the two experiments described above provide a probable range of future climate change. -from Authors