Climate impact response functions as impact tools in the tolerable windows approach

A critical issue for policymakers in defining mitigation strategies for climate change is the availability of appropriate evaluation tools. The development of climate impact response functions (CIRFs) is our reaction to this challenge. CIRFs depict the response of selected climate-sensitive impact sectors across a wide range of plausible futures. They consist of a limited number of climate-change-related dimensions and sensitivities of sector-specific impact models. The concept of CIRFs is defined and the procedure to develop them is presented. The use of climate change scenarios derived from various GCM experiments and the adopted impact assessment models are explained. The CIRFs presented here consider climate change impacts on natural vegetation, crop production, and water availability. They are part of the ICLIPS integrated assessment framework based on the tolerable windows approach. CIRFs can be applied both in 'forward' and in 'inverse' mode. In the latter, they help to translate thresholds for climate impacts perceived by stakeholders (so-called impact guardrails) into constraints for climate variables (so-called climate windows). This enables the results of detailed impact models to be incorporated into intertemporally optimizing integrated assessment models, such as the ICLIPS model.