نوع مقاله : پژوهشی بنیادی
نویسندگان
1 گروه مهندسی و مدیریت منابع آب، مؤسسه آموزش عالی توسعه دانش، سنندج، ایران
2 گروه علوم و مهندسی محیط زیست، دانشکده منابع طبیعی، دانشگاه کردستان، سنندج، ایران
3 گروه مرتع و آبخیزداری، دانشکده منابع طبیعی، دانشگاه کردستان، سنندج، ایران
چکیده
کلیدواژه‌ها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Climate change is the most significant challenge facing humanity in the 21st century, as it exerts numerous negative impacts on all dimensions of human life, both in urban and rural environments; however, its consequences are more pronounced in urban settings. It is essential to study the impacts of climate change on all aspects of urban life, including the city's climatic aspects such as precipitation and temperature, so that by understanding these impacts and projecting them into the future, better managerial planning for the city can be provided. In this research, the effects of climate change on seasonal and annual precipitation, maximum temperature, and minimum temperature in the city of Arak were projected under the new IPCC climate scenarios, including SSP1-2.6, SSP2-4.5, and SSP5-8.5, for future decades up to the year 2100. To utilize the outputs of the CanESM5 general circulation model at regional and local scales, the SDSM model was employed for downscaling. The results indicate a decrease in precipitation across all seasons and on an annual scale; such that an average annual precipitation reduction of -13.3% per decade is projected, with the greatest reduction occurring in summer (-29.2%) and the least in spring (-12.0%). Maximum temperature shows a decrease in winter (-16.4%) and an increase in other seasons, with an annual average of +0.4%. Minimum temperature exhibits a gradual increase in all seasons, with an annual average of +0.14% and the greatest increase in spring (+19.9%). The findings of this study suggest that the city of Arak will become drier over the next seven decades and warmer in all seasons except winter. Urban managers in Arak should, from now on, consider long-term managerial planning for appropriate urban designs and the adoption of modern and green technologies to cope with severe drought and heat in the city.
Extended Abstract
Introduction
Climate change is one of the most critical global challenges of the 21st century, with significant social, economic, environmental, and health impacts. Urban areas are particularly vulnerable because of high population density, concentrated infrastructure and industries, complex transportation systems, and socioeconomic pressures. In Iran, these impacts are intensified by predominantly arid and semi-arid conditions, with rising temperatures and declining precipitation expected to increase water scarcity, heat stress, air pollution, and environmental degradation. Since more than 75% of the population lives in urban areas, understanding future climate conditions is essential for effective urban planning, climate adaptation, and sustainable development. This issue is particularly important in Arak, the capital of Markazi Province and an important industrial, historical, sporting, and tourism center in Iran. Located at approximately 1,718 m above sea level, Arak has a cold semi-arid continental climate, with cold winters, hot and dry summers, and average annual precipitation of about 346 mm. Its location among mountains and near the Meighan Wetland increases its sensitivity to changing climatic conditions. Therefore, this study projects seasonal and annual changes in precipitation, maximum temperature, and minimum temperature in Arak up to 2100 under the IPCC Sixth Assessment Report Shared Socioeconomic Pathways (SSPs), including SSP1-2.6, SSP2-4.5, and SSP5-8.5. These scenarios represent different levels of socioeconomic development, mitigation efforts, and future greenhouse gas emissions, providing a range of plausible climate futures for Arak.
Methodology
Daily observational data for precipitation and temperature were sourced from the Arak synoptic station, covering the baseline period 1979–2014. To bridge the scale mismatch between global climate models and local applications, outputs from the CanESM5 global circulation model were statistically downscaled using the Statistical Downscaling Model (SDSM). This hybrid approach combines regression-based methods with weather generators, calibrated against large-scale NCEP reanalysis predictors for the same period. SDSM is widely applied in regional climate studies, including in Iran, due to its efficiency in handling station-level data and capturing local variability. Model performance was rigorously evaluated using multiple metrics: mean absolute error (MAE), root mean square error (RMSE), mean absolute percentage error (MAPE), mean bias error (MBE), Nash-Sutcliffe efficiency (NSE), and Willmott's index of agreement (WAI). These indicators confirmed the model's robust simulation capabilities for precipitation and temperatures at seasonal and annual scales.
Results and Discussion
The downscaling model's evaluation across six metrics demonstrated high fidelity in reproducing historical patterns, affirming its reliability for multi-decadal projections. This accuracy is crucial given precipitation's inherent variability, which often poses greater modelling challenges than temperature. Projections reveal a consistent decline in precipitation across all seasons and scenarios, with winter decreases averaging -12.4% per decade, spring -12.0%, summer -29.2%, and autumn -21.1%. Annually, the reduction averages -13.3% per decade, aligning with broader Iranian trends of diminishing rainfall under CMIP6 ensembles, potentially intensifying aridity in central regions like Markazi Province. Temperature projections exhibit nuanced seasonal patterns. Winter maximum temperatures decline markedly at -16.4% per decade across scenarios, suggesting cooler daytime highs possibly linked to altered atmospheric circulation or aerosol effects. In contrast, maximum temperatures rise in spring (+2.6% per decade), summer (+6.4%), and autumn (+7.0%), with an annual increase of +0.4% per decade. Minimum temperatures warm uniformly: +3.5% (winter), +19.9% (spring), +6.2% (summer), and +15.8% (autumn) per decade, yielding +14.0% annually. This asymmetric warming stronger in minima indicates reduced diurnal ranges in most seasons, a common climate change signal that heightens nighttime heat stress. Seasonal interactions highlight vulnerabilities: summer experiences the sharpest precipitation drop alongside modest minimum temperature rises, potentially straining water resources during peak demand. Spring shows milder precipitation declines but the largest minimum temperature increases, risking earlier heat onset. The widest maximum-minimum divergence occurs in winter (~20 percentage points), while summer shows near-convergence (~0.2 points). Precipitation's greater stochasticity complicates precise decadal pinpointing of extremes, unlike temperature trends. These findings resonate with national projections: Iran may face 10–35% precipitation reductions and 2–5°C warming by century's end, with central urban areas like Arak particularly affected due to existing semi-aridity.
Conclusion
Over the next seven decades to 2100, Arak is projected to become progressively drier across all seasons, with cooler winter maxima but warmer conditions overall, especially in non-winter periods and nighttime minima. These shifts portend increased risks of water shortages, heatwaves, reduced agricultural viability, and heightened urban heat island effects in this industrial center. Proactive adaptation is essential. Urban authorities should priorities resilient infrastructure, such as enhanced water management systems, heat-resistant building designs, and expanded green spaces incorporating modern technologies like efficient irrigation and renewable energy. Sustainable development must balance physical expansion with demographic pressures, urban fabric preservation, and climatic variability, adhering to technical and environmental standards. By integrating these measures, Arak can mitigate extreme dryness and heat, fostering a more resilient future amid global climate challenges. Continued research, including multi-model ensembles, will refine these projections and inform policy.
کلیدواژه‌ها [English]
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