دانشگاه کاشان مهندسی اکوسیستم بیابان 2538-6336 15 51 2026 08 23 Assessment of Climate Variables under CMIP6 Future Climate Scenarios in a Semi-Arid Region of Northwestern Iran Assessment of Climate Variables under CMIP6 Future Climate Scenarios in a Semi-Arid Region of Northwestern Iran 1 17 115623 ‎10.22052/deej.2026.258580.1140 FA Raoof Mostafazadeh Department of Natural Resources, Faculty of Agriculture and Natural Resources, Member of Water Management Research Center, University of Mohaghegh Ardabili, Ardabil, Iran Ali Nasiri Khiavi Ardabil Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Ardabil, Iran Shahnaz Mirzaei Department of Watershed Management, Faculty of Range and Watershed Management, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran Journal Article 2026 04 30 Climate change, largely driven by anthropogenic activities, has intensified the frequency and severity of extreme weather events, including floods, droughts, hailstorms, heatwaves, and anomalous cold spells. This study evaluates the performance of three CMIP6 models (ACCESS-CM2, MIROC6, and NESM3) in simulating daily precipitation and temperature for the flood-prone Gharesou watershed in Ardabil, Iran. The models were validated against observed data from 1984–2014 using statistical metrics, including Root Mean Square Error (RMSE), Percent Bias (PBIAS), and the Nash-Sutcliffe Efficiency (NSE). Following validation, future projections were downscaled and bias-corrected under SSP1-2.6, SSP2-4.5, and SSP3-7.0 scenarios using the delta change method. Based on the superior performance in PBIAS and NSE metrics across all stations—with minor exceptions in specific precipitation and maximum temperature parameters at the Ardabil and Namin stations—the ACCESS-CM2 model was selected for long-term projections. The results indicate a general downward trend in monthly precipitation, with localized exceptions during the June–August period in Ardabil, March–August at the Airport station, and July in Namin and Nir. A comparative analysis between observed and projected mean annual precipitation under the SSP1-2.6 scenario reveals site-specific variations: declines of 31.07 mm, 37.60 mm, and 116.69 mm at the Ardabil, Namin, and Nir stations, respectively, alongside a marginal increase of 1.44 mm at the Ardabil airport station. Furthermore, all scenarios project a consistent rise in mean annual maximum and minimum temperatures. Specifically, the projected increase in maximum temperature ranges from 1.2 °C (SSP2-4.5, Ardabil) to 2.05 °C (SSP1-2.6, Namin), while minimum temperatures are expected to rise by 3.65 °C (SSP2-4.5, Namin) to 7.75 °C (SSP1-2.6, Ardabil airport). These forecasts, characterized by decreasing precipitation and significant warming, underscore the likelihood of imminent climate-driven extremes. Consequently, these findings provide a critical foundation for water resource managers to develop targeted risk mitigation strategies and enhance environmental and hydrological resilience in the region. Climate change, largely driven by anthropogenic activities, has intensified the frequency and severity of extreme weather events, including floods, droughts, hailstorms, heatwaves, and anomalous cold spells. This study evaluates the performance of three CMIP6 models (ACCESS-CM2, MIROC6, and NESM3) in simulating daily precipitation and temperature for the flood-prone Gharesou watershed in Ardabil, Iran. The models were validated against observed data from 1984–2014 using statistical metrics, including Root Mean Square Error (RMSE), Percent Bias (PBIAS), and the Nash-Sutcliffe Efficiency (NSE). Following validation, future projections were downscaled and bias-corrected under SSP1-2.6, SSP2-4.5, and SSP3-7.0 scenarios using the delta change method. Based on the superior performance in PBIAS and NSE metrics across all stations—with minor exceptions in specific precipitation and maximum temperature parameters at the Ardabil and Namin stations—the ACCESS-CM2 model was selected for long-term projections. The results indicate a general downward trend in monthly precipitation, with localized exceptions during the June–August period in Ardabil, March–August at the Airport station, and July in Namin and Nir. A comparative analysis between observed and projected mean annual precipitation under the SSP1-2.6 scenario reveals site-specific variations: declines of 31.07 mm, 37.60 mm, and 116.69 mm at the Ardabil, Namin, and Nir stations, respectively, alongside a marginal increase of 1.44 mm at the Ardabil airport station. Furthermore, all scenarios project a consistent rise in mean annual maximum and minimum temperatures. Specifically, the projected increase in maximum temperature ranges from 1.2 °C (SSP2-4.5, Ardabil) to 2.05 °C (SSP1-2.6, Namin), while minimum temperatures are expected to rise by 3.65 °C (SSP2-4.5, Namin) to 7.75 °C (SSP1-2.6, Ardabil airport). These forecasts, characterized by decreasing precipitation and significant warming, underscore the likelihood of imminent climate-driven extremes. Consequently, these findings provide a critical foundation for water resource managers to develop targeted risk mitigation strategies and enhance environmental and hydrological resilience in the region. https://deej.kashanu.ac.ir/article_115623_50a176c519b97aa5a1c8f034e13bb3f8.pdf