Khan et al. (2026) Projected bioclimatic shifts in Pakistan: A CMIP6 ensemble analysis under shared socioeconomic pathways

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2026
• Date: 2026-01-01
• Authors: Wisal Khan, Mohamad Hidayat bin Jamal, Mohd. Khairul Idlan Muhammad, Najeebullah Khan, Shamsuddin Shahid
• DOI: 10.1007/s00704-025-05901-5

Research Groups

• Department of Water & Environmental Engineering, Faculty of Civil Engineering, Universiti Teknologi Malaysia (UTM), Johor Bahru, Malaysia
• Public Health Engineering Department, Government of Khyber Pakhtunkhwa, Peshawar, Pakistan
• Faculty of Engineering Sciences and Technology, Water and Marine Sciences (LUAWMS), Lasbela University of Agriculture, Uthal, Balochistan, Pakistan
• Regional Climate Change Centre, National Centre for Meteorology, Jeddah, Kingdom of Saudi Arabia
• Environmental and Atmospheric Sciences Research Group, Scientific Research Center, Al-Ayen University, Nasiriyah, Thi-Qar, Iraq

Short Summary

This study develops a comprehensive framework to project hydroclimatic changes across Pakistan using 22 CMIP6 Global Climate Models under three Shared Socioeconomic Pathways. It reveals robust, spatially coherent warming (up to 5 °C) and intensified monsoonal precipitation (up to 300 mm) by the late 21st century, identifying northern regions as hot-wet risk zones and southern provinces as hot-dry stress zones.

Objective

• To evaluate and project hydroclimatic changes across Pakistan using a comprehensive, performance-driven framework based on 22 CMIP6 Global Climate Models (GCMs) under three Shared Socioeconomic Pathways (SSP1–2.6, SSP2–4.5, SSP5–8.5) for early (2021–2060) and late (2061–2100) 21st-century periods, providing a robust, high-resolution foundation for targeted climate adaptation planning.

Study Configuration

• Spatial Scale: Pakistan, approximately 881,913 square kilometers, with data processed on a 0.25° × 0.25° grid.
• Temporal Scale: Historical (1975–2015), Early century (2021–2060), Late century (2061–2100).

Methodology and Data

• Models used:
  • 22 CMIP6 Global Climate Models (GCMs), with ACCESS-ESM1-5, INM-CM5-0, and MPI-ESM1-2-LR identified as top performers.
  • Statistical downscaling and bias-correction techniques: LARS-WG, Quantile Mapping (QM), Statistical Downscaling Model (SDSM).
  • Multi-Model Ensembles (MMEs): Arithmetic Mean (AM), Median, Bayesian Model Averaging (BMA), Independence-Weighted Mean (IWM).
• Data sources:
  • CMIP6 GCM projections for maximum temperature, minimum temperature, and precipitation (1960–2100) under SSP1-2.6, SSP2-4.5, and SSP5-8.5.
  • ERA5 reanalysis data (hourly total precipitation and 2-meter temperature, 0.25° × 0.25° spatial resolution, 1960–2014) as a benchmark.

Main Results

• Model Performance: ACCESS-ESM1-5, INM-CM5-0, and MPI-ESM1-2-LR were identified as the top-performing CMIP6 GCMs for simulating precipitation and temperature in Pakistan, based on the Symmetrical Uncertainty (SU) metric against ERA5.
• Bias Correction: Quantile Mapping (QM) performed best for temperature (KGE ≈ 0.86–0.90, r ≈ 0.9, RMSE < 4.2 °C), while LARS-WG performed best for precipitation (KGE ≈ 0.04).
• Ensemble Aggregation: Arithmetic Mean, Bayesian Model Averaging, and Independence-Weighted Mean methods showed high agreement with ERA5 for temperature (r > 0.97, RMSE < 2 °C) and reasonable performance for precipitation.
• Temperature Projections:
  • Annual mean temperature (Bio-1) is projected to increase by 1.2–1.5 °C under SSP1-2.6 (early century) and up to 4–5 °C under SSP5-8.5 (late century).
  • Maximum (Bio-5) and minimum (Bio-6) temperatures are projected to rise by 5–6 °C in northern highlands (Gilgit-Baltistan, Khyber Pakhtunkhwa, Baluchistan) under SSP5-8.5 (late century).
  • Annual temperature range (Bio-7) is projected to contract by 3–4 °C in southern plains under SSP5-8.5 (late century).
  • Seasonal temperatures (Bio-8–Bio-11) indicate warming exceeding 6 °C in the wettest and warmest quarters under SSP5-8.5 (late century).
  • Mean Diurnal Temperature Range (Bio-2) is projected to decrease by 0.4–1.0 °C in southern and central Pakistan under SSP5-8.5 (late century).
  • Temperature Seasonality (Bio-4) is projected to decline significantly (40–60 units) in Punjab and Sindh under SSP5-8.5 (late century).
• Precipitation Projections:
  • Annual rainfall (Bio-12) and wettest-month precipitation (Bio-13) are projected to increase by up to 300 mm, particularly in Azad Kashmir and Punjab, under SSP5-8.5 (late century).
  • Arid provinces (Sindh and southwestern Baluchistan) show limited rainfall change but strong thermal amplification (> 4 °C).
  • Precipitation Seasonality (Bio-15) is projected to increase (5–10 units) in Azad Kashmir, Punjab, and Khyber Pakhtunkhwa under SSP5-8.5 (late century).
  • Precipitation of the Coldest Quarter (Bio-19) shows a northward intensification (up to 40 mm increase in Gilgit Baltistan) and southern drying (25–35 mm decrease in Azad Kashmir, Khyber Pakhtunkhwa, Punjab) under SSP5-8.5 (late century).
• Regional Risk Zones: Northern regions (Azad Kashmir, Khyber Pakhtunkhwa, Gilgit Baltistan, northern Punjab) are identified as hot-wet risk zones, while southern provinces (Sindh, southwestern Baluchistan) are identified as hot-dry stress zones.

Contributions

• Developed a comprehensive, performance-driven framework for evaluating and projecting hydroclimatic changes using CMIP6 GCMs, integrating performance-based model calibration, multi-method bias correction, and multi-model ensemble optimization.
• Provided high-resolution, spatially explicit projections of 19 bioclimatic indicators for Pakistan, addressing a significant research gap in translating broad climate projections into fine-scale insights across diverse landscapes.
• Identified specific regional climate change "hotspots" and dual trajectories of thermal amplification and hydroclimatic intensification (hot-wet risk zones in the north, hot-dry stress zones in the south), offering a robust foundation for targeted climate adaptation planning.
• Bridged the gap between statistical performance evaluation and spatial risk mapping by jointly examining thermal and hydrological dynamics under multiple Shared Socioeconomic Pathways (SSPs).

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Citation

@article{Khan2026Projected,
  author = {Khan, Wisal and Jamal, Mohamad Hidayat bin and Muhammad, Mohd. Khairul Idlan and Khan, Najeebullah and Shahid, Shamsuddin},
  title = {Projected bioclimatic shifts in Pakistan: A CMIP6 ensemble analysis under shared socioeconomic pathways},
  journal = {Theoretical and Applied Climatology},
  year = {2026},
  doi = {10.1007/s00704-025-05901-5},
  url = {https://doi.org/10.1007/s00704-025-05901-5}
}