Escalating Future Climate Extremes Across the Black Sea Basin Driven by Kilometer-Scale Scenario Simulations

The Black Sea Basin (BSB) serves as a focal point for examining the impacts of climate change on extremes due to its complex topography. Coarse-resolution regional climate models remain limited in resolving the processes governing short-duration extremes over complex terrain, motivating recent modeling efforts that demonstrate the need for high-resolution simulations using convection-permitting models (CPMs) to obtain realistic results in such topography. In this study, we performed climate simulations at the convection-permitting scale (3 km) for 2005–2014 and 2061–2070 periods over the BSB, by downscaling the CMIP6 MPI-ESM1.2-HR model’s outputs under the Shared Socioeconomic Pathways 3–7.0 (SSP3-7.0) scenario using the WRF model. The validation of historical simulation shows that the model reproduces near-surface temperatures with a significant reduction in bias (~ 2 °C) compared to low-resolution MPI-ESM1.2-HR at high-elevation sites. Extreme daily and sub-daily precipitation is realistically represented, with events exceeding 50 mm/3 h and 100 mm/day are simulated in agreement with gridded observations. Future projections indicate an increase in daily maximum temperatures up to 7 °C in March, accelerating snowmelt over the Upper Euphrates Basin. The resulting decline in spring snow cover enhances snow–albedo feedback in the highlands, intensifying the frequency of extremely warm days and amplifying heatwave duration to ~ 55 days per year. In terms of precipitation, we identified a basin-wide intensification of extremes, with daily maximums exceeding 500 mm in Georgia and Romania, and sub-daily totals reaching up to 100 mm/3 h across the basin. Notably, the Istanbul metropolitan area emerges as a hotspot, where daily maximum precipitation is projected to more than double in the future, consistent with recently observed extreme events in the city. Overall, this study highlights the added value of convection-permitting simulations in capturing fine-scale climate processes and extremes, providing more robust and consistent projections for climate risk assessment, adaptation planning, and infrastructure resilience across the BSB.