Geoscientific Model Development Discussions www.geosci-model-dev-discuss.net 1991-9611 1991-962X 2 2 2009 10.5194/gmdd-2-1115-2009 http://www.geosci-model-dev-discuss.net/2/1115/2009/ http://www.geosci-model-dev-discuss.net/2/1115/2009/gmdd-2-1115-2009.html http://www.geosci-model-dev-discuss.net/2/1115/2009/gmdd-2-1115-2009.pdf 1115 1155 2009-08-26 The efficient global primitive equation climate model SPEEDO C. A. Severijns c.severijns@knmi.nl W. Hazeleger Royal Netherlands Meteorological Institute (KNMI), de Bilt, The Netherlands The efficient primitive-equation coupled atmosphere-ocean model SPEEDO is presented. The model includes an interactive sea-ice and land component. SPEEDO is a global earth system model of intermediate complexity. It has a horizontal resolution of T30 (triangular truncation at wave number 30) and 8 vertical layers in the atmosphere, and a horizontal resolution of 2 degrees and 20 levels in the ocean. The parameterizations in SPEEDO are developed in such a way that it is a fast model suitable for large ensembles or long runs on a workstation. The model has no flux correction. We compare the mean state and inter-annual variability of the model with observational fields of the atmosphere and ocean. In particular the atmospheric circulation, the mid-latitude patterns of variability and teleconnections from the tropics are well simulated. To show the model's capabilities, we performed a long control run and an ensemble experiment with enhanced greenhouse gasses. The long control run shows that the model is stable. CO₂ doubling and future climate change scenario experiments show a climate sensitivity of 1.84 K W^−1 m^−2, which is within the range of state-of-the-art climate models. The spatial response patterns are comparable to state-of-the-art, higher resolution models. However, for very high greenhouse concentrations the parameterizations are not valid. 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