PROJECTED CLIMATE CHANGE AND HYDROCLIMATIC EXTREMES BASED ON THE CMIP6 MULTI-MODEL ENSEMBLE: A CASE STUDY OF THE ARAL–SYR DARYA BASIN

Abstract

The Aral–Syr Darya Basin, a complex mountain–plain river system, is already experienc-ing strong climatic and anthropogenic stress affecting water security. This study analyzes observed climatic changes and provides a probabilistic assessment of future climate con-ditions in the region. The analysis is based on climate projections under the SSP3-7.0 and SSP5-8.5 scenarios from CMIP6 multi-model ensemble relative to the 1981–2010 baseline period. Changes in mean temperature, precipitation intensity (RX1day), maximum dura-tion of dry periods (CDD), and the number of extremely hot days (TX35) were examined. The results indicate substantial warming by the end of the 21st century, reaching +6.0–6.8 °C. The number of extremely hot days is projected to exceed 61 days per year. Total precipitation may increase by 17–20%, accompanied with greater irregularity with stronger rainfall events and longer dry intervals. A shift in peak precipitation from sum-mer to the winter-spring period was revealed, leading to “wet year–dry summer” dissoci-ation. These changes are expected to intensify water scarcity risks, particularly in arid lowlands, and accelerate desertification processes. The findings highlight the urgent need to strengthen transboundary water management cooperation within the Syr Darya Basin to support regional adaptation to climate change.