Monte Carlo Climate Change Forecasts with a Global Coupled Ocean-Atmosphere Model

摘要

The Monte Carlo approach, which has increasingly been used during the last decadein the field of extended range weather forecasting, was applied for climate change experiments. Four integrations with a global coupled ocean-atmosphere model were started from different initial conditions, but with the same greenhouse gas forcing according to the IPCC scenario A. All experiments were run for a period of 50 years. The results indicate that the time evolution of the global mean warming depends strongly on the initial state of the climate system. It can vary between 6 and 31 years. The Monte Carlo approach delivers information about both the mean response and the statistical significance of the response. While the individual members of the ensemble show a considerable variation in the climate change pattern of temperature after 50 years, the ensemble mean climate change pattern closely resembles the pattern obtained in a 100 year integration and is, at least over most of the land areas, statistically significant. The ensemble averaged sea level change due to thermal expansion is significant in the global mean and locally over wide regions of the Pacific. The hydrological cycle is also significantly enhanced in the global mean, but locally the changes in precipitation and soil moisture are masked by the variability of the experiments.