Cai et al. (2026) Global water cycle changes in a warming climate: Projection from CMIP6 multi-model ensemble mean

Identification

• Journal: Atmospheric Research
• Year: 2026
• Date: 2026-02-12
• Authors: Yinan Cai, Z. J. Chen, Qingping Sun, Yi Du
• DOI: 10.1016/j.atmosres.2026.108864

Research Groups

• National Supercomputing Center in Shenzhen, Shenzhen, China
• State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
• College of Marine Science, University of Chinese Academy of Sciences, Beijing, China
• Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
• Department of Ocean Science and Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Hong Kong University of Science and Technology, Kowloon, Hong Kong, China

Short Summary

This study projects a robust and progressively intensifying global hydrological cycle throughout the 21st century under warming climate scenarios (SSP2-4.5 and SSP5-8.5) using CMIP6 models, revealing a pronounced land–ocean asymmetry with greater precipitation increases over land and enhanced ocean-to-land moisture transport.

Objective

• To quantify projected changes in key global hydrological components (evaporation, precipitation, total column water vapor, and ocean-to-land moisture transport) under medium-emission (SSP2-4.5) and high-emission (SSP5-8.5) scenarios using a multi-model ensemble from CMIP6.
• To systematically quantify historical baselines and future changes across land and ocean domains, and evaluate their sensitivities to emission pathways across three future time horizons.

Study Configuration

• Spatial Scale: Global, with differentiation between land and ocean domains, and analysis of regional patterns (e.g., Northern Hemisphere high latitudes, equatorial Pacific, Sahel region). Data interpolated to a 1° × 1° horizontal resolution.
• Temporal Scale: Historical period (1850–2014) and future projections (2015–2100) categorized into near-term (2021–2040), mid-term (2041–2060), and long-term (2081–2100) periods, relative to a 1995–2014 baseline.

Methodology and Data

• Models used: Multi-model ensemble from Coupled Model Intercomparison Project Phase 6 (CMIP6), including 16 models for E, P, TCWV, and T, and a 5-model subset for IVT (e.g., ACCESS-CM2, CanESM5, CESM2, CNRM-CM6-1, GFDL-ESM4, HadGEM3-GC31-LL, IPSL-CM6A-LR, MIROC6, MPI-ESM1-2-HR, MRI-ESM2-0, NESM3, NORESM2-MM, UKESM1-0-LL).
• Data sources: CMIP6 simulations (historical, SSP2-4.5, SSP5-8.5) obtained from the Earth System Grid Federation (ESGF) data portal. ERA5 (fifth-generation ECMWF reanalysis) used as a reference dataset for model evaluation.

Main Results

• The global hydrological cycle is projected to intensify robustly throughout the 21st century, with substantially stronger changes under the high-emission SSP5-8.5 scenario.
• Total Column Water Vapor (TCWV) increases by 5.5% (2021–2040) and 16.8% (2081–2100) under SSP2-4.5, and by 6.3% and 34.8% under SSP5-8.5, relative to 1995–2014. Global mean TCWV enhancement is approximately 7.78% per kelvin of warming under SSP5-8.5 (2081–2100).
• A pronounced land–ocean asymmetry emerges: terrestrial precipitation increases are approximately 1.10–1.40 times greater than oceanic rates, indicating stronger land amplification. Global mean precipitation is projected to rise by approximately 1.55% per kelvin of warming.
• Ocean-to-land moisture transport rises by 6.2% under SSP2-4.5 and 13.5% under SSP5-8.5 by the end of the century (2081–2100), contributing significantly to enhanced land precipitation.
• Global mean evaporation is projected to increase at a rate of approximately 1.58% per kelvin of warming during 2081–2100 under SSP5-8.5.
• Spatial patterns show global warming, with largest increases over Northern Hemisphere high latitudes (north of 60°N), reaching approximately 10 K under SSP5-8.5 (2081–2100). Precipitation intensification hotspots include the equatorial Pacific, western Indian Ocean, and Sahel region, while some regions (e.g., southeastern Pacific, mid-latitude Atlantic) experience drying.

Contributions

• Provides a comprehensive, component-linked structural perspective on how the global water cycle reorganizes under warming, explicitly quantifying evaporation components and oceanic precipitation in future projections, which are not always reported as dedicated ocean-only terms in existing syntheses like IPCC AR6.
• Consolidates the quantitative sensitivity of the global water cycle to different emission pathways (SSP2-4.5 and SSP5-8.5) and across multiple future time horizons.
• Highlights the robust land–ocean asymmetry in hydrological responses and the increasing importance of atmospheric moisture redistribution in shaping continental water availability.
• Offers critical insights to support climate adaptation strategies by quantifying the magnitude of future intensification, its land–ocean asymmetry, and temporal evolution.

Funding

• National Key Research and Development Program of China (2023YFB3002400)
• National Natural Science Foundation of China (42106021, 42175043)
• Youth Innovation Promotion Association CAS (2022347)

Citation

@article{Cai2026Global,
  author = {Cai, Yinan and Chen, Z. J. and Sun, Qingping and Du, Yi},
  title = {Global water cycle changes in a warming climate: Projection from CMIP6 multi-model ensemble mean},
  journal = {Atmospheric Research},
  year = {2026},
  doi = {10.1016/j.atmosres.2026.108864},
  url = {https://doi.org/10.1016/j.atmosres.2026.108864}
}