Graphical representation of climate change impacts and associated uncertainty to enable better policy making in hydrological disaster management

The effects of climate change are felt differently on regional scales, necessitating region specific analysis. Prediction of climate change and its impacts is riddled with uncertainties, which is exacerbated when moving to finer scale analysis. Climate change impact predictions on regional scales, when used for policy making or in design procedure should consider the uncertainty in the projected result. Ignoring the uncertainty can lead to poor policy decisions and inadequate structures. A major limitation in combining uncertainties in policy action is in how the uncertainty is communicated by the scientific community to policy makers and stakeholders. Simple graphical approaches have been found to be effective in communicating research outcomes to the public. The present study proposes a graphical approach for reporting regional scale climate change impacts and their associated uncertainty from an ensemble projection of regional extreme events. The concept of risk, which combines the information of event magnitude, frequency and regional vulnerabilities, is used to convey the impacts of extreme events over a catchment. The risk is defined as an index to facilitate comparison between different magnitude events, across different time periods, and across multiple scenarios. The uncertainty is represented as the range of risk predicted for each event and a level of confidence is developed based on the ensemble prediction. The projected risks of multiple extreme events are plotted in comparison with calculated risk of historical events that occurred in the region, to enable a policy maker to relate the index with actual consequences.