Al-Hussein et al. (2026) Assessment of meteorological drought based on CMIP6 multi-model ensemble projections in Iraq

Identification

• Journal: Climatic Change
• Year: 2026
• Date: 2026-01-29
• Authors: Asaad A. M. Al-Hussein, Safa Khalil, Bushra M. Ali
• DOI: 10.1007/s10584-026-04123-6

Research Groups

Department of Sensing and Nano-Photonics, Laser and Photonics Center, University of Al-Hamdaniya, Nineveh, 41006, Iraq

Short Summary

This study assesses historical and future meteorological drought in Iraq using CMIP6 multi-model ensemble projections under SSP1-2.6 and SSP5-8.5 scenarios, revealing a significant increase in drought frequency and severity, particularly under the high-emission SSP5-8.5 scenario by the late 21st century.

Objective

• To analyze precipitation and temperature trends via the Mann‒Kendall test and Sen’s slope estimator.
• To analyze the spatiotemporal variance in historical meteorological drought trends.
• To predict future meteorological drought trends via the standardized precipitation index (SPI) and reconnaissance drought index (RDI).
• To bridge the gap in assessing future meteorological drought conditions in Iraq under climate change using CMIP6 multi-model ensemble outputs and Common Socioeconomic Pathways (SSP1-2.6 and SSP5-8.5) emission scenarios.

Study Configuration

• Spatial Scale: Iraq, covering 438,314 km², using data from 18 climate stations distributed across Iraqi governorates. Spatial resolution of 0.25º × 0.25º (approximately 25 km × 25 km).
• Temporal Scale: Historical period (1995–2014), Near Future (2040–2059), and Far Future (2080–2100).

Methodology and Data

• Models used: Coupled Model Intercomparison Project Phase 6 (CMIP6) multi-model ensemble projections. Drought Indices Calculator (DrinC) software for SPI and RDI calculation. Mann‒Kendall test and Sen’s slope estimator for trend analysis. Hargreaves and Samani (1985) method for potential evapotranspiration (PET) calculation.
• Data sources: Climate Change Knowledge Portal (CCKP) website (https://climateknowledgeportal.worldbank.org/country/iraq), providing bias-adjusted and spatially approximated gridded data derived from global climate models (GCMs) of CMIP6.

Main Results

• The CMIP6 multi-model ensemble demonstrated high accuracy in simulating precipitation and temperature, with correlation coefficients (R) ranging from 0.98 to 1.0 and Nash–Sutcliffe efficiency (NSE) values above 0.89.
• Under the SSP1-2.6 scenario, precipitation is projected to slightly increase (2.91% in the near future, 1.81% in the far future). Under the SSP5-8.5 scenario, precipitation is projected to decrease significantly (2% in the near future, 8.73% in the far future).
• Both minimum and maximum temperatures are projected to increase under all scenarios. Under SSP1-2.6, maximum temperatures increase by 1.7 °C and minimum temperatures by 1.52 °C. Under SSP5-8.5, maximum temperatures increase by 4.19 °C and minimum temperatures by 4.09 °C by the far future.
• Historically, Iraq experienced "nearly normal" drought conditions. Under the SSP1-2.6 scenario, conditions are expected to remain "nearly normal" to "moderately wet".
• Under the SSP5-8.5 scenario, drought conditions are projected to worsen from "near-normal" in the near future to "severe drought" across most of Iraq in the far future, particularly in the northern and northwestern regions.
• The SPI and RDI showed similar drought patterns and high correlation (0.84 to 0.99), indicating precipitation variability as the primary driver of meteorological drought.
• The empirical cumulative distribution function (ECDF) shows that the probability of severe drought (SPI/RDI < -0.5) increases from 0% historically and under SSP1-2.6 to 50% in 2040–2059 and 100% in 2080–2100 under the SSP5-8.5 scenario.

Contributions

This study addresses a critical gap in the assessment of future meteorological drought conditions in Iraq under climate change. It provides a comprehensive multi-scenario framework using the latest CMIP6 multi-model ensemble projections and two widely used drought indices (SPI and RDI) for spatiotemporal analysis of historical and future drought trends. The findings offer valuable, updated insights for climate and water resource experts and decision-makers to develop effective mitigation and adaptation strategies for Iraq.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Citation

@article{AlHussein2026Assessment,
  author = {Al-Hussein, Asaad A. M. and Khalil, Safa and Ali, Bushra M.},
  title = {Assessment of meteorological drought based on CMIP6 multi-model ensemble projections in Iraq},
  journal = {Climatic Change},
  year = {2026},
  doi = {10.1007/s10584-026-04123-6},
  url = {https://doi.org/10.1007/s10584-026-04123-6}
}