COMPARISON OF WHEAT SIMULATION-MODELS UNDER CLIMATE-CHANGE .2. APPLICATION OF CLIMATE-CHANGE SCENARIOS

A comparison of the performance of 5 wheat models (AFRCWHEAT2, CERES, NWHEAT, SIRIUS and SOILN) was carried out for 2 sites in Europe: Rotha msted, UK, and Seville, Spain. The aims of this study were (1) to comp are predictions of wheat models for climate change scenarios, and (2) to investigate the effects of changes in climatic variability in clima te change scenarios on model predictions. Simulations were run for cli mate change scenarios derived from a number of 2 x CO2 equilibrium and transient GCM (global circulation model) experiments. For most climat e change scenarios the model results were broadly similar. Where resul ts differed, much of the difference could be explained by model sensit ivity to climate and differences in initial conditions. Transient scen arios without changes in climatic variability usually resulted in larg e yield increases for Rothamsted and in nil to large yield increases f or Seville. Incorporation of changed climatic variability in the trans ient scenario had a more profound effect on grain yield and resulted i n a substantial decrease in mean yield with a strong increase in yield variation at Seville. This was associated with the changes in the dur ation of dry spells and a redistribution of precipitation over the veg etation period. The results show that future studies of the effect of climate change on crop yields must consider changes in climatic variab ility as well as changes in mean climate.