Chen et al. (2026) Persistent river heatwaves are emerging worldwide under climate change

Identification

• Journal: Nature Communications
• Year: 2026
• Date: 2026-01-06
• Authors: Yiling Chen, Zhiying Su, R. Iestyn Woolway, Niko Wanders, Sijia Wu, Ziwei Huang, Manhui Luo
• DOI: 10.1038/s41467-025-66868-5

Research Groups

• Guangdong Provincial Key Laboratory of Urbanization and Geo-Simulation, School of Geography and Planning, Sun Yat-sen University, Guangzhou, China
• School of Ocean Sciences, Bangor University, Bangor, UK
• Department of Physical Geography, Utrecht University, Utrecht, the Netherlands

Short Summary

This study provides a global assessment of persistent river heatwaves, projecting a significant increase in their intensity and duration by the end of the 21st century under climate change, with nearly half of the world's rivers experiencing year-round heatwave states under high-emission scenarios. It also quantifies the substantial and disproportionate future population exposure to these events, particularly in vulnerable low-income regions.

Objective

• To provide a comprehensive global assessment of river heatwaves and explore their future changes under different Representative Concentration Pathways (RCPs).
• To estimate future population exposure to river heatwaves by integrating projected population data under different Shared Socioeconomic Pathways (SSPs).

Study Configuration

• Spatial Scale: Global, at a 5 arc-minute resolution (approximately 10 km at the equator).
• Temporal Scale: Historical period from 1976 to 2005, and future projections from 2006 to 2099.

Methodology and Data

• Models used:
  • Global hydrological and water temperature models: PCR-GLOBWB, DynWat.
  • Earth System Models (ESMs) from ISI-MIP: GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR, MIROC-ESM-CHEM, NorESM1-M.
• Data sources:
  • FutureStreams dataset (global weekly average streamflow and water temperature).
  • E2O reanalysis dataset (weekly river water temperature for bias correction).
  • WATCH Forcing Data (WFD) dataset (for bias correction of ESMs).
  • Global Self-consistent, Hierarchical, High-resolution Geography Database (GSHHG) (river polygons).
  • HydroBASINS dataset (watershed boundary data).
  • Köppen-Geiger climate classification maps.
  • US National Center for Atmospheric Research (NCAR) (future population counts based on SSPs).
  • United States Geological Survey (USGS) (in situ measurements for regional validation).
  • Representative Concentration Pathways (RCPs): RCP 2.6, RCP 4.5, RCP 6.0, RCP 8.5.
  • Shared Socioeconomic Pathways (SSPs): SSP1, SSP2, SSP4, SSP5 (combined with RCPs).
  • River heatwave definition: Weekly average temperature exceeding the 90th percentile threshold for the same calendar week over the 1976–2005 baseline period.

Main Results

• River heatwaves are projected to become significantly more intense and persistent globally by the end of the 21st century.
• Under the high-emission scenario (RCP 8.5) for 2070–2099, the average intensity of river heatwaves is projected to increase by approximately 4.2-fold to 2.69 °C, and the average duration by approximately 95-fold to 216.35 weeks, relative to the 1976–2005 baseline.
• Nearly half (49.20%) of global rivers are projected to reach a year-round heatwave state by 2070–2099 under RCP 8.5.
• Tropical rivers, such as those in the Amazon and Congo basins, are particularly vulnerable, with projected increases in heatwave duration by 358-fold and 318-fold, respectively, and intensity increases of 8-fold and 9-fold.
• Global annual population exposure to river heatwaves is projected to reach 16.8 billion person-weeks by the end of the century under SSP5-RCP8.5.
• Low-income countries, particularly in Sub-Saharan Africa and India, are expected to face a disproportionately heavier burden of population exposure to river heatwaves.
• Reducing greenhouse gas emissions (e.g., RCP 2.6) can substantially mitigate the intensification of river heatwaves and reduce population exposure.

Contributions

• Provides the first comprehensive global assessment of river heatwaves, including their historical trends and future projections under various climate change scenarios.
• Quantifies the projected increases in river heatwave intensity, duration, and frequency, highlighting the emergence of persistent year-round heatwave states in major river basins.
• Integrates climate and socioeconomic pathways to estimate future population exposure to river heatwaves globally, identifying hotspots and regional disparities, particularly the disproportionate burden on low-income regions.
• Emphasizes the critical need for targeted mitigation of greenhouse gas emissions and regional adaptation strategies to protect river ecosystems and human communities.

Funding

• National Natural Science Foundation of China (No. 42371028)
• UKRI Natural Environment Research Council (NERC) Independent Research Fellowship (No. NE/T011246/1)

Citation

@article{Chen2026Persistent,
  author = {Chen, Yiling and Su, Zhiying and Woolway, R. Iestyn and Wanders, Niko and Wu, Sijia and Huang, Ziwei and Luo, Manhui},
  title = {Persistent river heatwaves are emerging worldwide under climate change},
  journal = {Nature Communications},
  year = {2026},
  doi = {10.1038/s41467-025-66868-5},
  url = {https://doi.org/10.1038/s41467-025-66868-5}
}