Cold Start Problem in Transient Simulations with Coupled Atmosphere-Ocean Models

摘要

Using linear response theory, a general expression for the cold start error intransient numerical experiments with coupled atmosphere-ocean general circulation models is derived. The theory is applied to the Hamburg CO2 scenario simulations. An attempt to estimate the global mean temperature response function of the coupled model from the response of the model to a CO2 doubling was unsuccessful because of the nonlinearity of the system. However, an alternative derivation based on the transient simulation itself yielded a cold start error which was able to explain the initial retardation of the Hamburg global warming curve relative to the IPCC (Intergovernmental Panel on Climate Change) results obtained with a simple box diffusion-upwelling model. In the case of the sea level the behavior of the model is apparently more ideal. The cold start error estimations based on a CO2 doubling experiment and on an experiment with gradually increasing CO2 (Scenario A) are very similar and explain about two thirds of the coupled model retardation relative to the IPCC results.