Tung, K

The observed forcing and response to the 11-year solar cycle provide a critical constraint on climate model performance. Previous GCM simulations mostly involved prescribed sea-surface temperatures, which prevented feedback processes, such as water-vapor feedback, ice-albedo feedback etc. from taking place. We have performed a multi-century simulation using a periodic solar-cycle forcing at 11-year period, which allows the identification of the surface temperature anomaly at the same period as the response. Since this model couples the atmosphere and the ocean, there is a heat flux into the ocean at solar max and vice versa at solar min. This mechanism is responsible for causing a lag of the surface temperature response relative to forcing in both the model and the observation. By comparing the lag in the model with that in the observation, we conclude that the current generation of AOGCMs may have somewhat larger heat fluxes into the ocean during periods of transient heating, as compared to reality . This result has implications on the model predicted transient warming due to the increasing greenhouse gases.