Invited Talk On Maize Model Intercomparisons for Climate Change Symposium.

Simulation models can be used as strategic tools for evaluating the consequences of climate change on crop production and possible adaptations of crop management practices. Different models may differ in the predicted crop response to climate change factors, because physiological processes are variously represented across the different mechanistic models, due to different objectives and context in which they were designed. As part of the Agricultural Model Intercomparison and Improvement Project, a group of maize modelers explored model output sensitivity to climatic factors for 19 maize crop models across four sentinel sites chosen in four contrasting pedoclimatic zones of maize production: Lusignan (France), Ames (Iowa), Rio Verde (Brazil) and Morogoro (Tanzania). For each site, models were run with 30-year baseline measured weather as well as weather files modified for temperature and CO₂.  The sensitivity of models to temperature and CO₂ were evaluated under both low input and high input information (initial conditions) for the sentinel sites. The crop models exhibited widely different simulations of yield under different climatic conditions. Nevertheless, the mean of the simulations across all 19 maize models well matched the experimental results. Also, the range of the simulated climate change effects on maize yield and interannual variations were highly dependent on the model and on the site. Importantly, the maize models generally showed the same response to climatic factors with minimal versus detailed information inputs. The maize models were generally similar in predicting shorter crop life cycle and reduced yields as temperature increased above ambient at each site.  The models varied in their CO₂ effects on yield and evapotranspiration, although the general trend was small yield increase and evapotranspiration decrease with rising CO₂. The ability of ensemble modeling to simulate the response of maize to CO₂, temperature and water will be discussed.