Projected changes in precipitation and air temperature over the Volga River Basin from bias-corrected CMIP6 outputs

This paper investigates future changes in annual mean precipitation and air temperature across the Volga River basin, which serve as significant drivers of climate-induced changes in the Volga River's discharge, the primary input to the Caspian Sea. The thirteen Global Climate Models (GCMs) outputs under four Shared Socioeconomic Pathways (SSPs) scenarios (SSP1–2.6, SSP2–4.5, SSP3–7.0, and SSP5–8.5) from the sixth phase of Coupled Model Intercomparison Project (CMIP6) are used for this study. In the historical period (1950-2014), using comprehensive rating metrics and Taylor diagram, the GCMs are ranked according to their ability to capture the temporal and spatial variability of precipitation and air temperature. The Multi-Model Ensemble (MME) is generated, and bias-correction techniques are utilized to reduce the uncertainties and correct the biases in CMIP6 outputs. Bias-correction techniques are assessed in the historical period and the average of proper methods utilized for future projections (2015-2100). In the 21st century, future projections show that the Volga River basin could mainly experience a temperature increase of 0.4°C to 7.5°C, alongside a precipitation rise of 0.7% to 37%, depending on the scenarios considered. Comparison of future projections with an observational dataset from 2015 to 2017 indicates that the SSP2–4.5 is more likely scenario to represent the future climate of the Volga River basin.