Multi-Model Projection of Climate Extremes under 1.5°C–4°C Global Warming Levels across Iran

Abstract

This study investigates the spatial and temporal patterns of climate extremes in Iran and projects future changes using data from seven General Circulation Models (GCMs) that participated in the Coupled Model Intercomparison Project phase 6 (CMIP6). We assess the impacts of climate change under the SSP2-4.5 and SSP5-8.5 emission scenarios, considering global warming levels of 1.5°C, 2°C, 3°C, and 4°C above preindustrial levels. Gridded observations are derived from ground measurements, using the SYMAP algorithm at a 1/8° latitude–longitude resolution. Subsequently, statistical downscaling of GCMs is performed using the Multivariate Bias Correction (MBC) and Bias Correction Constructed Analogues with Quantile Mapping Reordering (BCCAQ) approaches. Projected changes in extreme temperature and precipitation events are evaluated using the CLIMDEX indices. The findings indicate consistent rises in annual temperatures across Iran, with temperature indices such as warm spell duration and the monthly minimum value of daily temperature exhibiting substantial increases, about twofold by the +4.0°C period. Additionally, the study highlights a potential intensification in precipitation extremes (Rx1day, Rx5day, R90p, R95p), suggesting a heightened risk of more frequent and severe floods, particularly in the western, northern, and northwestern regions. These insights underline the critical need for region-specific adaptation strategies to address the risks associated with climate change in Iran.