Response of water cycle over drylands to a warming future

The synergistic relationship among various hydrological elements within the water cycle remains unclear because existing studies have mainly focused on the response of a single water cycle element to global warming in drylands or on a single hotspot region. To address this knowledge gap, we leveraged Coupled Model Intercomparison Project Phase 6–based multi-model projections (2021‒2100) of the atmospheric and moisture budget to investigate the response of the full water cycle process to global warming in global drylands. The results reveal that the global dryland water cycle will accelerate within the projected period. Notably, the multi-model median responses regarding the annual precipitation (P; 6.71 (3.12‒10.07) mm/K), evapotranspiration (E; 5.46 (3.08‒8.59) mm/K), precipitation minus evapotranspiration (P−E; 0.05 (−1.33–1.21) mm/K) and runoff (R; 2.48 (0.19–3.07) mm/K) exhibit evidently increasing trends. Conversely, the total soil moisture is projected to decrease at a rate of −0.64 (−8.85–3.59) mm/K, which will exacerbate drought risk and reduce agricultural yields. We observe that global warming will exert varying effects on the water cycle. Regionally, it is expected to strengthen in East Asia’s drylands but weaken in South Africa’s. Seasonally, the P−E projection indicates that the global drylands will experience an intensified water cycle in the wet season (by 1.84 (−4.5–7.1) mm/K) but a slight decrease in the dry season (by −0.79 (−3.8–1.2) mm/K). Further, a moisture-budget decomposition reveals that the thermodynamic term, −32.1 (−35.82 to −23.9) mm/K, negatively contributes to precipitation mainly due to enhanced moisture divergence, whereas the dynamic term, 5.11 (1.54‒7.36) mm/K, partially offset these effects. Our findings are of great significance for adapting to future global dryland water cycle changes and sustainable management of water resources.