Abstract: While crop models are widely used to assess the change in crop productivity with climate change, their skill in assessing irrigation water demand or the risk of crop failure in large area impact assessments is relatively unknown. The objective of this study is to investigate which aspects of modeling crop water use (reference crop evapotranspiration (ET0), soil water extraction, soil evaporation, soil water balance and root growth) contributes most to the variability in estimates of maize crop water use and the risk of crop failure, and demonstrate the resulting uncertainty in a climate change impact study for Europe. The SIMPLACE crop modeling framework was used to couple the LINTUL5 crop model in factorial combinations of 2-3 different approaches for simulating the 5 aspects of crop water use, resulting in 51 modeling approaches. Using experiments in France and New Zeland, analysis of total sensitivity revealed that ET0 explained the most variability in both irrigated maize water use and rainfed grain yield levels, with soil evaporation also imporatant in the French experiment. In the European impact study, net irrigation requirement differed by 36% between the Penman and Hargreaves ET0 methods in the baseline period. Average EU grain yields were similar between models, but differences approached 1-2 tonnes in parts of France and Southern Europe. EU wide esimates of crop failure in the historical period ranged between 5.4 years for Priestley-Taylor to every 7.9 years for the Penman ET0 methods. While the uncertainty in absolute values between models was significant, estimates of relative changes were similar between models, confirming the utility of crop models in assessing climate change impacts. If ET0 estimates in crop models can be improved, through the use of appropriate methods, uncertainty in irrigation water demand as well as in yield estimates under drought can be reduced.

Abstract: Climate change impacts on food production, socioeconomic changes (population and income growth  in large parts of the world) and biofuel policies affecting demand quantities have risen scientific,  political and public interest in long-term forecasts on food security. Whereas first quantitative analyses  from global economic models are starting to appear (e.g. (von Lampe et al., under review)), similar  studies on smaller regional scales are not yet available. However, acknowledging that climate change  affects crop yields differently across scales and regions (e.g. (Reidsma et al., 2007)) and considering  the specific political setting given through the Common Agricultural Policy (CAP) in Europe, the  MACSUR project focuses on the impact of climate change and socioeconomic changes on European  agriculture and its contribution to global food security. We present a Europe-wide analysis of the  effect of selected climate and socioeconomic scenarios on food security in terms of food prices using  the Common Agricultural Policy Regionalised Impact modelling system (CAPRI). No Label