Sridhara et al. (2026) Historical and future extremes of cauvery basin analysed using cmip6 models and ETCCDI indices

Identification

• Journal: Scientific Reports
• Year: 2026
• Date: 2026-03-12
• Authors: Shankarappa Sridhara, Hemareddy Thimmareddy, Mahesh Haroli, Santanu Kumar Bal, Bappa Das, Prakash Kumar Jha, P N S B S V Prasad V
• DOI: 10.1038/s41598-026-42818-z

Research Groups

• Centre for Climate Resilient Agriculture & All India Coordinated Research Project on Agrometeorology, Keladi Shivappa Nayaka University of Agricultural and Horticultural Sciences, Shivamogga, Karnataka, India
• ICAR- Central Research Institute for Dryland Agriculture, Hyderabad, Telangana, India
• ICAR-Central Coastal Agricultural Research Institute, Old Goa, Goa, India
• Department of Plant and Soil Sciences, Mississippi State University, Mississippi State, MS, USA
• Department of Agronomy, Kansas State University, Manhattan, KS, USA

Short Summary

This study validates and ranks 13 CMIP6 models against IMD observations using Multi-Criteria Decision-Making (MCDM) techniques to project historical (1951–2023) and future (2025–2100) extreme temperature and precipitation events in the Cauvery Basin, India, revealing significant increases in heat stress and alternating flood/drought risks under high-emission scenarios.

Objective

• To validate and rank 13 CMIP6 models against IMD gridded observations using Multi-Criteria Decision-Making (MCDM) techniques for projecting extreme temperature and precipitation events in the Cauvery Basin, and to analyze historical and future trends of these extremes using ETCCDI indices under SSP245 and SSP585 scenarios.

Study Configuration

• Spatial Scale: Cauvery River Basin, southern India (approximately 81,155 km²).
• Temporal Scale:
  • Historical: 1951–2023 (IMD data), 1951–2014 (CMIP6 validation).
  • Future: 2025–2100, divided into near future (2025–2050), mid-century (2051–2075), and far future (2076–2100).

Methodology and Data

• Models used:
  • 13 CMIP6 General Circulation Models (GCMs): ACCESS-CM2, ACCESS-ESM1-5, BCC-CSM2-MR, CanESM5, EC-Earth3, EC-Earth3-Veg, INM-CM4-8, INM-CM5-0, MPI-ESM1-2-HR, MPI-ESM1-2-LR, MRI-ESM2-0, NorESM2-LM, NorESM2-MM.
  • Multi-Criteria Decision-Making (MCDM) techniques for ranking: TOPSIS, VIKOR, PROMETHEE II, EDAS, SAW, AHP, ELECTRE, combined with Rank Sum Method.
  • Extreme Climate Change Detection and Indices (ETCCDI) for analyzing extremes.
  • Bias correction using Empirical Quantile Mapping (EQM).
• Data sources:
  • India Meteorological Department (IMD) gridded observations: Daily maximum temperature (Tmax) and minimum temperature (Tmin) at 1° × 1° resolution, daily precipitation at 0.25° × 0.25° resolution.
  • CMIP6 model outputs for historical and future (SSP245, SSP585) scenarios.

Main Results

• CMIP6 Model Performance: INM-CM5-0 was the top performer for precipitation, INM-CM4-8 for maximum temperature (Tmax), and ACCESS-CM2 for minimum temperature (Tmin). No single model excelled across all parameters and MCDM techniques.
• Historical Trends (1951–2023):
  • Temperature: Statistically significant increases in TXx (annual maximum daily maximum temperature) ranging from 34.5 °C to 37 °C, TNn (annual minimum daily minimum temperature) from 14 °C to 15 °C, and SU35 (summer days > 35 °C) historically 20–25 days per year. DTR (diurnal temperature range) averaged 9.5–10.5 °C with an increasing trend.
  • Precipitation: High interannual variability, with PRCPTOT (annual total precipitation) fluctuating between 769.27 mm and 1232.40 mm. RX5day (maximum 5-day precipitation) peaked at 214.32 mm. CDD (consecutive dry days) peaked at 101.78 days. SDII (simple daily intensity index) remained stable at 10–13 mm/day.
• Future Projections (2025–2100) under SSP245 and SSP585:
  • Temperature:
    • TXx is projected to rise by 1.5–2.0 °C under SSP245 and exceed 3.5 °C under SSP585 by 2076–2100.
    • SU35 is projected to exceed 50 days per year (SSP245, near future) and surpass 90 days per year (SSP585, far future).
    • TX90p and TN90p show substantial increases, indicating more warm days and nights.
    • DTR is projected to decline significantly, especially under SSP585 (slope = -0.065 °C/year in far future), indicating intensified heat stress.
  • Precipitation:
    • PRCPTOT is projected to rise significantly, particularly under SSP245 in the mid- and far future (slope = 8.71 mm/year).
    • RX5day could exceed 300 mm (far future).
    • R95p (very wet days precipitation) may approach 450 mm (far future).
    • SDII could rise to 16 mm/day (far future), indicating intensification of short-duration, high-intensity rainfall events.
    • CDD is expected to remain above 70 days in the near/mid-future, with a slight decrease in the far future under SSP585, pointing to alternating flood and drought risks.
• Mann-Kendall Trend Analysis: Confirms significant increasing trends for temperature extremes (TXx, TNn, SU35, TX90p) and a declining trend for DTR in the future, particularly under SSP585. Precipitation trends show increased variability, with increasing PRCPTOT, R95p, and SDII, but mixed or decreasing trends for RX5day and CDD depending on scenario and period.

Contributions

• First study to validate and rank 13 CMIP6 models for the Cauvery Basin using a comprehensive suite of Multi-Criteria Decision-Making (MCDM) techniques.
• Provides robust selection of best-performing CMIP6 models for precipitation, maximum temperature, and minimum temperature specifically for the Cauvery Basin.
• Offers detailed historical (1951–2023) and future (2025–2100) projections of 11 ETCCDI extreme temperature and precipitation indices under SSP245 and SSP585 scenarios for a critical water-stressed region in India.
• Quantifies the projected increases in heat stress (e.g., SU35 by >90 days per year under SSP585) and highlights the dual risk of intensified wet extremes (e.g., RX5day >300 mm) and persistent drought conditions (CDD >70 days).
• Emphasizes the critical role of emissions scenarios (SSP245 vs. SSP585) in shaping future climate risks and provides actionable insights for targeted adaptation strategies in agriculture and water management.

Funding

• Not Applicable

Citation

@article{Sridhara2026Historical,
  author = {Sridhara, Shankarappa and Thimmareddy, Hemareddy and Haroli, Mahesh and Bal, Santanu Kumar and Das, Bappa and Jha, Prakash Kumar and V, P N S B S V Prasad},
  title = {Historical and future extremes of cauvery basin analysed using cmip6 models and ETCCDI indices},
  journal = {Scientific Reports},
  year = {2026},
  doi = {10.1038/s41598-026-42818-z},
  url = {https://doi.org/10.1038/s41598-026-42818-z}
}