Hamdouni et al. (2026) Evaluation of CMIP6-based climate projections in Northern Morocco: A bias corrected assessment of temperature and precipitation trends in three mediterranean watersheds

Identification

• Journal: Environmental Challenges
• Year: 2026
• Date: 2026-02-11
• Authors: Yassir El Hamdouni, Hamza BRIAK, El Mahdi EL KHALKI, Mohamed Beroho, Abdellatif MOUSSAID, Abdelali Gourfi, Ismail Bouizrou, Mourad Aqnouy, Khadija Aboumaria
• DOI: 10.1016/j.envc.2026.101430

Research Groups

• Department of Earth Sciences, Faculty of Sciences and Techniques of Tangier (FST), Abdelmalek Essaadi University (UAE), Morocco
• Center for Sustainable Soil Sciences (C3S), College of Agriculture and Environmental Sciences (CAES), University Mohammed VI Polytechnic (UM6P), Ben Guerir, Morocco
• International Water Research Institute, Mohammed VI Polytechnic University (UM6P), Benguerir, Morocco
• Geosciences Research and Development Laboratory, Department of Earth Sciences and Environment, Faculty of Sciences and Techniques of Al Hoceima (FSTH), Abdelmalek Essaadi University, Tetouan, Morocco
• Ecole Nationale Supérieure de l’Administration, Rabat, Morocco
• Functional Ecology and Environmental Engineering Laboratory, Faculty of Sciences and Techniques, Sidi Mohamed Ben Abdellah University, Fez, Morocco
• Geosciences and Technologies Research Team, Faculty of Sciences and Techniques, Moulay Ismaïl University of Meknes, Errachidia, Morocco

Short Summary

This study evaluates historical and future climate trends in three Northern Moroccan watersheds using bias-corrected CMIP6 models, projecting a significant temperature increase (2.5–3.5 °C by 2100) and a substantial precipitation decline (up to 30%) under high-emission scenarios, with the Oued Laou watershed identified as most vulnerable to aridification.

Objective

• To evaluate the skill of high-resolution CMIP6 models (MPI-ESM1-2-HR and GFDL-ESM4) in simulating localized precipitation and temperature regimes across Northern Morocco’s complex topography.
• To quantify the magnitude of future climate trends (2015–2100) under three Shared Socioeconomic Pathways (SSP2.6, SSP4.5, and SSP8.5) using the Quantile Delta Mapping (QDM) technique to ensure statistical consistency.
• To validate model performance against recent observational data (2015–2022) to establish a reliable climate baseline for future water resource management and adaptation planning in the region.

Study Configuration

• Spatial Scale: Three strategic Mediterranean watersheds in Northern Morocco: Oued Laou (928 km²), Kalaya (38 km²), and 9 Avril (240 km²).
• Temporal Scale: Historical period (1987–2014), Validation period (2015–2019/2022), Future projection period (2015–2100).

Methodology and Data

• Models used:
  • CMIP6 Global Climate Models (GCMs): MPI-ESM1-2-HR (horizontal resolution ~0.65° or ~67 km) and GFDL-ESM4 (horizontal resolution ~1° or ~100 km).
  • Bias correction method: Quantile Delta Mapping (QDM), including Quantile Mapping (QM) for historical calibration and Synchronized Quantile Mapping for validation.
  • Statistical analysis: Mann-Kendall test for trend detection and Sen’s Slope estimator for trend magnitude.
  • Performance metrics: Pearson correlation coefficient (r), Mean Ratio (β), Coefficient of Variation Ratio (γ), Kling-Gupta Efficiency (KGE), Nash-Sutcliffe Efficiency (NSE), Root Mean Square Error (RMSE), and Percentage Bias (PBIAS).
• Data sources:
  • High-quality daily observational climate data (precipitation and temperature) from the Loukkos Hydraulic Basin Agency (LHBA).
  • CMIP6 raw model outputs from the Copernicus Climate Data Store (CDS).
  • Shared Socioeconomic Pathways (SSPs): SSP2.6, SSP4.5, and SSP8.5.

Main Results

• Historical Trends (1987–2014):
  • Temperature: Significant warming trends were observed in the 9 Avril and Oued Laou watersheds (p < 0.05), particularly in summer and autumn. Oued Laou showed the highest annual warming rate of +0.046 °C/year, reaching +0.048 °C/year in summer. Kalaya watershed showed non-significant warming.
  • Precipitation: No statistically significant monotonic trends were detected across any watershed (p > 0.05), but Sen’s slope indicated drying magnitudes, with Oued Laou showing an annual decrease of -1.42 mm/year and -1.55 mm/year in winter.
• Model Validation (2015–2019/2022):
  • Temperature: Bias-corrected CMIP6 simulations showed exceptional agreement with observations, with average Kling-Gupta Efficiency (KGE) scores of 0.880, correlation coefficients (r) > 0.96, and low Root Mean Square Error (RMSE < 1.54 °C).
  • Precipitation: Models captured regional variability with moderate KGE scores (0.469 to 0.538). Oued Laou and Kalaya had low PBIAS (-0.94% and -2.60%), while 9 Avril showed overestimation (PBIAS = +20.95%).
• Future Projections (2015–2100):
  • Temperature: Consistent and significant increases across all SSPs. Projected rise of 2.5–3.5 °C by 2100 for Oued Laou. Under SSP8.5, annual warming rates reached up to +0.059 °C/year (Oued Laou), +0.052 °C/year (Kalaya), and +0.054 °C/year (9 Avril).
  • Precipitation: A general decline is projected. Under the high-emission SSP8.5 scenario, a statistically significant drying trend is expected, with Oued Laou projected to experience a 20–30% decline in annual precipitation by 2100 (-2.12 mm/year).
• Watershed Sensitivity: The Oued Laou watershed was identified as the most sensitive to future aridification.

Contributions

• Provides a critical high-resolution, station-based, and bias-corrected climate dataset for temperature and precipitation in three strategic Northern Moroccan watersheds, addressing a significant knowledge gap in the region.
• Demonstrates the effectiveness of the Quantile Delta Mapping (QDM) method in correcting GCM biases while preserving the climate change signal, enhancing the reliability of future projections for local impact assessments.
• Offers robust climate projections under various SSP scenarios, which are vital inputs for hydrological modeling and the development of climate-resilient management strategies for water and agriculture in Northern Morocco.
• Highlights the differential vulnerability of specific watersheds (e.g., Oued Laou as a hotspot for aridification), providing targeted information for regional adaptation planning.

Funding

Not specified in the paper.

Citation

@article{Hamdouni2026Evaluation,
  author = {Hamdouni, Yassir El and BRIAK, Hamza and KHALKI, El Mahdi EL and Beroho, Mohamed and MOUSSAID, Abdellatif and Gourfi, Abdelali and Bouizrou, Ismail and Aqnouy, Mourad and Aboumaria, Khadija},
  title = {Evaluation of CMIP6-based climate projections in Northern Morocco: A bias corrected assessment of temperature and precipitation trends in three mediterranean watersheds},
  journal = {Environmental Challenges},
  year = {2026},
  doi = {10.1016/j.envc.2026.101430},
  url = {https://doi.org/10.1016/j.envc.2026.101430}
}