Multiple-Century Response of a Coupled Ocean-Atmosphere Model to an Increase of Atmospheric Carbon Dioxide

Abstract 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 C02 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 C02 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. One of the most notable features of the C02-quadrupling integration is the gradual disappearance of thermohaline circulations in most of the model oceans during the first 250-year period, leaving behind wind-driven cells. For example, thermohaline circulation nearly vanishes in the North Atlantic during the fist 200 years of the integration. In the Weddell and R...