Global evaluation of the "dry gets drier, and wet gets wetter" paradigm from a terrestrial water storage change perspective

The "dry gets drier, and wet gets wetter" (DDWW) paradigm hasbeen widely used to summarize the expected trends of the global hydrologiccycle under climate change. However, the paradigm is largely conditioned bychoice of different metrics and datasets used and is still comprehensivelyunexplored from the perspective of terrestrial water storage anomalies (TWSAs).Considering the essential role of TWSAs in wetting and drying of the landsystem, here we built upon a large ensemble of TWSA datasets, includingsatellite-based products, global hydrological models, land surface models,and global climate models to evaluate the DDWW hypothesis during thehistorical (1985-2014) and future (2071-2100) periods under variousscenarios with a 0.05 significance level (for trend estimates). We find that11.01 %-40.84 % (range by various datasets) of global land confirms theDDWW paradigm, while 10.21 %-35.43 % of the area shows the oppositepattern during the historical period. In the future, the DDWW paradigm isstill challenged, with the percentage supporting the pattern lower than18 % and both the DDWW-validated and DDWW-opposed proportion increasingalong with the intensification of emission scenarios. We show that thedifferent choices of data sources can reasonably influence the test resultsup to a 4-fold difference. Our findings will provide insights andimplications for global wetting and drying trends from the perspective ofTWSA under climate change.