Changes in Temperature and Precipitation in Kazakhstan During XX–XXI-Centuries Based on Observational and CMIP6 Model Data

Observed and projected climate change is global in character, but its impacts vary considerably across regions, and continental interiors show enhanced sensitivity to changes in radiative forcing and atmospheric circulation. Over recent decades, Kazakhstan has warmed at a rate exceeding the global average. Based on observations from the national network of meteorological stations and on an ensemble of 33 CMIP6 climate models, the study examines the observed changes in temperature and precipitation over 1991–2024, as well as projected changes during the twenty-first century under the SSP2-4.5 and SSP5-8.5 scenarios. The focus is placed on the mean annual conditions, seasonal differentiation, and spatial variability across the five regions of Kazakhstan, defined according to the regional economic and agricultural zoning. Substantial warming was observed in the present-day climate over almost the entire territory of Kazakhstan, with the largest rise in the Caspian area and in Southern Kazakhstan. Higher rates of warming were recorded in spring and summer, whereas winter showed a slight cooling that is not statistically significant. While the warmest regions of the country experienced the strongest temperature rise, the coldest regions showed no significant warming, thereby increasing the thermal contrast across Kazakhstan. Precipitation changes during 1991–2024 are mostly statistically insignificant. A significant summer decrease was found only in the Almaty and Kyzylorda oblasts, whereas autumn precipitation increased significantly in the central and north-eastern parts of the country, by 21% and 26% relative to the respective regional means, and locally by up to 40%. In the 21st century, under the SSP2-4.5 and SSP5-8.5 scenarios, a steady warming is projected, reaching an average of 3.1 °C and 6.1 °C, respectively, by 2081–2100. The warming exhibits a zonal pattern, with the largest annual temperature rise in Northern Kazakhstan (up to 6.7 °C by 2081–2100 under SSP5-8.5) and the smallest in the Southern and Western regions (5.7–5.8 °C). For precipitation, the inter-model spread is large and the signal is mostly not robust. Under both scenarios, precipitation is projected to increase in winter and spring and to decrease in summer, but only the winter increase under SSP5-8.5 is robust over most of the country, as is the annual increase in the east. The summer decrease, strongest in the west, does not exceed the internal variability of the models. Although the models project an increase in precipitation, the climate is projected to become more arid according to the De Martonne index, because the effect of warming exceeds the precipitation gain by a factor of two to four. By 2081–2100, 33% (SSP2-4.5) and 49% (SSP5-8.5) of the territory of Kazakhstan are projected to move into a drier class of the De Martonne aridity index, whereas continentality is projected to change little. The five regions of Kazakhstan differ in both observed and expected changes. The Western region, already the driest region and the one with the strongest observed warming (+0.89 °C between 1991 and 2007 and 2008–2024), loses summer precipitation by the end of the century (−17%) and is the only region projected to cross into the arid class, with implications for water supply and irrigation. The Northern region, the country’s grain belt, is projected to warm most in winter (+7.7 °C) and to shift to the semi-arid class as early as 2041–2060 under SSP5-8.5. The Eastern region is projected to gain the most precipitation (+14%) but loses most aridity index. The Central and Southern regions remain semi-arid, the Southern region is the only one in which the projected drying is not robust.