Quantifying and Communicating Uncertain Climate Change Hazards in Participatory Climate Change Adaptation Processes

Abstract. Participatory processes for identifying local climate change adaptation measures have to be performed all around the globe. It is therefore of utmost importance to investigate methods for the optimal design of such processes. A central aspect is how to address the epistemic uncertainties of future developments, in particular how to appropriately inform the stakeholders about the uncertain potential climate change hazards. In a participatory process on water-related adaptation in a biosphere reserve in Germany, we used the freely available output of a multi-model ensemble to quantify the wide range of potential future changes in (ground)water resources. We analyzed groundwater recharge and runoff computed according to the ISIMIP2b protocol by eight global hydrological models, each of which was driven by the output of four global climate models. To support participatory climate change adaptation processes, we propose to present uncertain local climate change hazards with percentile boxes rather than with boxplots or with simple averages and a verbal description of model agreement on the sign of change. This enables stakeholders to identify the future changes they wish to adapt to depending on the problem (e.g., resource scarcity vs. resource excess) and their risk aversion. Using or adapting our analysis and communication approach, flexible climate change risk management strategies can and should be developed worldwide in a participatory and transdisciplinary manner involving stakeholders and scientists.