Ensemble Simulations of the 20th and 21st Century Climates by a Coupled GCM

The DOE supported Parallel Climate Model (PCM), which makes use of the NCAR Community Climate Model (CCM3) and Land Surface Model and a parallel ocean model (POP), was used to simulate the climates of the 20th century and the climate changes in the 21st century under various scenarios. The 20th century simulation includes historical greenhouse gas and sulfate aerosol forcings and is repeated by 10 ensemble runs. The 21st century simulation, which has 5 ensemble runs for each of two scenarios, a Business as Usual case and a CO2 stabilization case. Both scenarios are based on realistic projections of future growth in world economy, population, energy-usage, etc. We will present the ensemble means and ensemble ranges in global mean temperature and precipitation over the 20th and 21st centuries. Regional patterns of change will be discussed. Changes in other fields (including the atmospheric general circulation) in the 21st century will also be examined.