This study assesses the impact of climate change on global water scarcity using a large ensemble of global hydrological models (GHMs) forced by five global climate models (GCMs) and the latest greenhouse gas concentration scenarios (Representative Concentration Pathways). The results show that climate change is likely to exacerbate regional and global water scarcity significantly. Specifically, a global warming of 2°C above preindustrial levels will increase the number of people living under absolute water scarcity (<500 m³ per capita per year) by approximately 40% compared to the effect of population growth alone. The study also highlights large uncertainties in these estimates, with both GCMs and GHMs contributing to the spread. The uncertainties are particularly dominant in regions with declining water resources, suggesting potential for improved water resource projections through further development of hydrological models. The findings emphasize the need for adaptive strategies to address the increasing water scarcity challenges posed by climate change and population growth.This study assesses the impact of climate change on global water scarcity using a large ensemble of global hydrological models (GHMs) forced by five global climate models (GCMs) and the latest greenhouse gas concentration scenarios (Representative Concentration Pathways). The results show that climate change is likely to exacerbate regional and global water scarcity significantly. Specifically, a global warming of 2°C above preindustrial levels will increase the number of people living under absolute water scarcity (<500 m³ per capita per year) by approximately 40% compared to the effect of population growth alone. The study also highlights large uncertainties in these estimates, with both GCMs and GHMs contributing to the spread. The uncertainties are particularly dominant in regions with declining water resources, suggesting potential for improved water resource projections through further development of hydrological models. The findings emphasize the need for adaptive strategies to address the increasing water scarcity challenges posed by climate change and population growth.