Climate change due to the gradual increase in atmospheric CO2:: A climate system model sensitivity study

A numerical experiment investigating climate change due to the gradual increase in atmospheric carbon dioxide (CO2) has been performed with the community climate system model (CCSM) developed by National Center for Atmospheric Research (NCAR). Composed of four independent component models simulating the earth's atmosphere, ocean, land surface, and sea-ice and one central coupler, the CCSM is used to simulate and understand the earth's past, present and future climate states. The model experiment consists of a control run with a fixed atmospheric CO2 concentration at a standardized value for 1990 to 2000 (355 ppmv) and a transient run with a gradually increased atmospheric CO2 at the rate of 1% per year. jaThe initial CO2 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 CO2 is defined as the difference between the results from the transient and control runs. At the time Of CO2 doubling (about year 70), the globally averaged surface air temperature increases by 1.25degreesC. The surface air temperature increases are more predominant over the higher-latitude land areas than over other areas, especially in boreal winter. With an increase in the surface air temperature, there is a decrease in the diurnal temperature range, with the nighttime minimum temperature increasing more than the daytime maximum temperature. And air temperature shows tropospheric warming and stratospheric cooling causing the strong temperature gradient and polar jet intensifications.