Projecting the Future Bioclimatic Environment of Bratislava: A UTCI-Based Analysis Under Representative Concentration Pathway Scenarios

Abstract This article deals with a future projection of the bioclimatic environment in Bratislava, Slovakia, under ongoing climate change. Using Meteonorm-generated climate data of up to 2100, this research paper presents calculations of the Universal Thermal Climate Index (UTCI) for three Representative Concentration Pathway scenarios, i.e., RCP2.6, RCP4.5, and RCP8.5. The analysis of hourly UTCI values quantifies projected shifts in human thermal stress, with the linear regression revealing strong temporal trends (R² > 0.97, p < 0.05). The main conclusions point to a significant transformation of the city’s climate. Under the high-emissions RCP8.5 scenario, the annual duration of strong heat stress (UTCI ≥ +32°C) is projected to surge from a contemporary baseline of 66 hours to 936 by 2100. Concurrently, annual cold stress (UTCI ≤ 0°C) hours are expected to decrease from 851 to 312. The high degree of variability in the RCP8.5 scenario (CV = 61%) indicates increasing uncertainty in extreme conditions. This dual shift confirms the city’s thermal character will be fundamentally altered, thereby leading to prolonged, stressful summers and milder winters. These findings provide a quantitative evidence base for local policymakers to develop urgent public health and urban adaptation strategies and can further support architects and civil engineers in the future design of resilient buildings through simulation-based solutions.