Amplified Global Seasonality in Water Availability over Land in Recent Decades

Climate warming is intensifying seasonal water cycle patterns, with significant consequences for societies and ecosystems. However, the changes in seasonal precipitation minus evapotranspiration (P 2 E) over recent decades, and the factors contributing to these changes, remain poorly understood}despite a documented decline in annual water availability (annual P 2 E). In this study, we used multiple observational datasets to quantify global seasonal P 2 E shifts from 2000 to 2020. Our findings reveal a significant increasing trend (0.15 mm month²¹ yr²¹, p, 0.01) in seasonal range in P 2 E, primarily driven by a significant global decrease in minimum P 2 E values, which affected more than 64% of the land areas. This decline was particularly pronounced in both hemispheres, while contrasting trends in maximum P 2 E between the hemispheres masked any clear global trend. The reduction in minimum P 2 E was largely attributed to increased evapotranspiration (76%), highlighting its critical role in amplifying seasonal P 2 E. Climate models are generally able to capture the seasonal variations of P 2 E, especially at longer time scales, despite existing spatial disparities. Therefore, using suitable climate models to project future P 2 E seasonality can provide usable information for future adaptation in a warming world. This study underscores the growing imbalance in global seasonal water availability with climate warming.