Climate Change Due to the Gradual Increase in Atmospheric CO sub(2): A Climate System Model Sensitivity Study

A numerical exeperiment investigating climate change due to the gradual increase in atmospheric carbon dioxide (CO sub(2)) has been perfomed with the community climate system model (CCSM) developed by Natinal Center for Atmospheric Research (NCAR). Composed of four independent component models simulatiag the earth's atmosphere, ocean, land surface, and sea-ice and one central coupler. the CCSM is used to simulate and understsnd the earth's past, present and future climate states. The model experiment consists of a control run with a fixed atmospheric CO sub(2) concentration at a standardized value for 1990 to 2000 (355 ppmv) and a transient run with a gradually increased atmospheric CO sub(2) at the rate of 1% per year.ja The initial CO sub(2) concentration of the transient run is 355 ppmv. Each run has been performed for 80 simulated years. In this experiment, climate change due to the gradually increased atmospheric CO sub(2) is defined as the difference between the results from the transient and control runs. At the time of CO sub(2) doubling (about year 70), the globally averaged surface air temperature increases by 125 degree C. The surface air temperature increases are more predominent over the higher-latitude land areas than other areas, especially in boreal winter. With an increase in the surface air temperature, there is a decrease in the diuxnal temperature rango, with the nighttime minimum temperature shows cropospheric worming and stratospherie cooling causing the strong temperature gradient and poler jet intensifications.