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Abstract

The most recent IPCC reports highlighted that every degree counts when considering the impacts of global warming, especially for glacier evolution, and it has been recently confirmed by Rounce et al., 2023. Our study aims to simulate glacier evolution globally by 2100 and assess their impacts for downstream hydrology. We used the Open Global Glacier Model (https://oggm.org/) that permits to simulate the future of all glaciers individually in the 19 regions of the RGI inventory for the 21^st century, simulating surface mass balance and ice dynamics in a coherent global framework. Climate forcing are derived from CMIP6 simulations, and are grouped by different 2100 global warming targets. Results show 3 kinds of glacier and related hydrology behavior during the 21^st century: 1. regions where the maximum contribution of glaciers to river runoff, called peak water, is already reached, associated with a large decrease of glacier runoff and a low influence of the 2100 warming target; 2. regions where the peak water will probably be reached in the coming decades with generally a moderate influence of the climate scenario and a decrease of the monthly maximum glacier melt; 3. regions where the peak water will probably not be reached in the 21^st century with a large influence of the 2100 warming target and an increase of glacier contribution to river runoff during the whole 21^st century. Finally, results confirmed the importance of every half-degree of global warming but also highlighted very different behaviors between glacierized regions for downstream hydrology.