Abstract
The outcomes of the 2015 Paris Agreement triggered a number of climate impact assessments, such as for floods and droughts, to focus on future time frames corresponding to the years of reaching specific levels of global warming. Yet, the links between the timing of the warming levels and the corresponding greenhouse gas concentration pathways to reach them remain poorly understood. To address this gap, we compared projected changes of annual mean, extreme high, and extreme low river discharges in Europe at 1.5 °C and 2 °C under Representative Concentration Pathways RCP8.5 and RCP4.5 from an ensemble of regional climate model (RCM) simulations. The statistical significance of the difference between the two scenarios for both warming levels was then evaluated. The results show that in the majority of Europe (>95% of the surface area for the annual mean discharge, >98% for high and low extremes), the changes projected in the two pathways were statistically indistinguishable. These results suggest that in studies of changes at global warming levels, the projections of the two pathways can be merged into a single ensemble without major loss of information. With regard to the uncertainty of the unified ensemble, the findings show that the projected changes of annual mean, extreme high, and extreme low river discharge were statistically significant in large portions of Europe.
Highlights
River runoff is associated with different types of natural hazards
The ensemble changes projected for QH100, QM, and QL15 at 1.5 ◦ C and 2.0 ◦ C were similar in the two pathways with projected changes generally more intense at 2 ◦ C than at 1.5 ◦ C
The variance of the projected changes was studied with the ANOVA methodology to investigate the statistical significance of the differences between the two scenarios
Summary
River runoff is associated with different types of natural hazards. High flow regimes are associated with floods, a major natural hazard with considerable human and socio-economic implications [1]. Changes in mean river discharge affect the long-term availability of water resources necessary for the sustainability of ecosystems and agricultural activities [3,4]. In view of global warming, the scientific community has put significant effort into studying how both mean and extreme river runoff values will change on the basis of climate projections, both at the global scale, such as in the Coupled Model Intercomparison Project 5 (CMIP5, [11]), and at the regional scale, such as in the Coordinated Regional Climate Downscaling Experiment (CORDEX, [12]), as well as to quantify the uncertainty in the projected changes [13].
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