earth-syst-dynam-discuss.net/5/1075/2014/ doi:10.5194/esdd-5-1075-2014 © Author(s) 2014. CC Attribution 3.0 License. This discussion paper is/has been under review for the journal Earth System Dynamics (ESD). Please refer to the corresponding final paper in ESD if available. Correspondence to: K. Frieler (katja.frieler@pik-potsdam.de) Published by Copernicus Publications on behalf of the European Geosciences Union. Abstract In order to achieve climate change mitigation, long-term decisions are required that must be reconciled with other societal goals that draw on the same resources. For example, ensuring food security for a growing population may require an expansion of crop land, thereby reducing natural carbon sinks or the area available for bio-energy 5 production. Here, we show that current impact-model uncertainties pose an important challenge to long-term mitigation planning and propose a new risk-assessment and decision framework that accounts for competing interests. Based on cross-sectorally consistent simulations generated within the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP) we discuss potential gains and lim-10 itations of additional irrigation and trade-offs of the expansion of agricultural land as two possible response measures to climate change and growing food demand. We de-scribe an illustrative example in which the combination of both measures may close the supply demand gap while leading to a loss of approximately half of all natural carbon sinks. 15 We highlight current limitations of available simulations and additional steps required for a comprehensive risk assessment.