Effectiveness of water-related adaptation decreases with increasing warming

Adaptation is central to address climate impacts. At present, we have a limited understanding of the effectiveness of adaptation to reduce risks in a warming world, because adaptation remains insufficiently addressed in climate impact projections. Where projections exist, these are assessed mostly in case study settings. The importance of water is apparent within the field of climate adaptation, with the majority of documented and projected adaptation related to water. Based on a meta-review of projections of adaptation, we assess the ability of different modeled water-related adaptation options to reduce climate risk at 1.5°C, 2°C, 3°C, and 4°C of warming and show that the effectiveness of the assessed options decreases with increasing warming across all world regions and options. Although adaptation benefits can be achieved for many regions, increasing maladaptive outcomes are projected at higher levels of warming. Our analysis highlights the urgent need to limit global warming by drastically reducing emissions to avoid catastrophic impacts.