Seasonal cycle experiment on the climate sensitivity due to a doubling of CO₂ with an atmospheric general circulation model coupled to a simple mixed-layer ocean model.

A simple slab ocean of 50 m depth, which allows for seasonal ocean heat storage but no ocean heat transport, is coupled to a global spectral general circulation model with global domain, realistic geography, and computed clouds. Globally averaged, the annual mean surface air temperature increase computed over the last 3 years of an integration with a full annual cycle for 2 x CO₂ compared to the control for 1 x CO₂ is 3.5^oC. Zonal mean air temperature differences indicate stratospheric cooling and tropospheric warming as seen in other CO₂ modeling studies. Greatest increases of surface air temperature in the 2 x CO₂ case, compared to the control, occur near the sea ice margins.-from Authors