Coupled impacts of climate change and urban morphology on building energy demand and outdoor thermal comfort in Harbin, China

The combined effects of climate change and the urban heat island intensify building energy demand and pose significant challenges to urban thermal resilience. This study develops an integrated framework combining a Coupled Model Intercomparison Project Phase 6 (CMIP6) model, a high-resolution Local Climate Zone (LCZ) map, and a calibrated Urban Weather Generator to quantify urban thermal microclimate and building energy demand in Harbin from 2025 to 2099. MIROC-ES2L was used to generate LCZ-specific weather files considering three Shared Socioeconomic Pathways (SSPs), including SSP126, SSP245, and SSP585. Results indicate pronounced warming and drying across all LCZs, with annual mean temperature rising by 4.5–4.7 °C and relative humidity decreasing by up to 12% under SSP585. Significant intra-urban heterogeneity is observed, as compact LCZs remain 1.6 °C warmer than natural LCZs. By the 2070s, cooling demand in compact LCZs increases by 11% while heating demand decreases by over 23%. Although total annual energy decreases, peak cooling surpasses peak heating by mid-century. Crucially, compact morphologies induce profound seasonal synergies and trade-offs. In winter, compact LCZs create a synergistic optimization that lowers both heating demand and pedestrian cold stress. Conversely, summer warming triggers a lose-lose scenario of surging cooling loads and severe outdoor heat stress, reaching approximately 2550 h annually in the most compact zone. Relying on conventional typical meteorological year data underestimates these future heat risks by a factor of 1.19. This framework provides a robust basis for morphology-sensitive climate adaptation and urban energy resilience planning.