ИСТИНА

According to IPCC 6th Assessment Report, the global surface temperature will continue to increase until at least mid-century under all emissions scenarios. Global warming comes with increasing frequency of extreme weather events, in particular of heat waves (IPCC, 2021). The risks posed by extreme high temperatures are determined by changing climate but also depend on socioeconomic factors such as population density, urbanization level. We provide estimates of current and future population exposure to heat waves in Russian regions under the projection scenarios introduced by IPCC for the mid-21 century. Data from three CMIP6 models for scenarios SSP1-2.6 («soft») and SSP5-8.5 («hard»), which start in 2015 and assume different levels of radiation exposure by 2100, were used. Two indices were used, which together reflect the magnitude and duration of heat waves in summer: maximum daily temperatures (Tmax) and number of very warm days (Tx90), i.e. number of days with maximum temperature above the 90th percentile of observed temperature in the base period. We also used estimates of the population of Russian regions according to Rosstat data for 2020 and forecast figures for 2050. Changes in the exposure of the population to the effects of heat waves are associated with both climate change and population changes as a result of natural increase/decrease and migration. The impact of heat waves on the population was defined as the number of people living in regions subject to maximum daily temperatures above 30°C, multiplied by the number of very warm days. From our estimates, by the 2050, the area exposed to maximum daily temperatures above 30°C increases in Russia by 1.6–2.2 times from 12 to 18.7–26.7% covering most of European Russia and much of the southern Urals and Siberia. The aggregate population exposure increases by 1.8–2.5 times from 2.46 bln person-days in the current period to 4.49 and 6.05 bln person-days under the soft and hard scenarios respectively. Against the overall population decline, the growth in exposure is mainly driven by climate factor through the expansion of the exposed area to densely populated regions in the middle Russia, in southern Urals and Siberia. The projections show a stronger exposure to extreme temperatures for the Black Earth (Chernozem) region, the Lower Volga region, and especially for the Black Sea region, the Caucasus, and the Caspian Sea region where the absolute maximum summer temperatures exceed 35°C and 40°C.