Accelerated thermal shift in semi-arid urban environments: Urban heat island dynamics and seasonal energy balance disruption in Marrakesh, Morocco

Abstract

Rapidly urbanizing semi-arid regions face compounding thermal stress from global climate change and intensifying urban heat islands, yet their interactive effects on building energy demand remain poorly quantified. Here we present one of the first systematic coupling of projected UHI evolution under IPCC Representative Concentration Pathways with building energy performance for Moroccan semi arid city, addressing a critical knowledge gap for North African urban environments. Using an integrated modeling framework combining Meteonorm climate projections, the Urban Weather Generator, and EnergyPlus simulations across three morphologically distinct urban fabrics in Marrakesh traditional Old city, planned modern district, and informal settlement, we demonstrate fundamental thermal regime transitions dependent on emission trajectories. Total electricity consumption diverges dramatically by pathway: RCP 2.6 yields modest increases (+2.6% by 2090, reaching 125,773 Wh/m²), while RCP 8.5 produces a severe escalation of +19.2% (reaching 146,104 Wh/m²). Critically, cooling demand explodes by 40% (from 67,593 to 94,630 Wh/m²) under RCP 8.5, while heating collapses by 85% (from 4,170 to 632 Wh/m²), eliminating traditional winter energy advantages. The study reveals a stable UHI cooling penalty of approximately 1,077-1,088 Wh/m² in July across all zones under current conditions. However, under RCP 8.5, a seasonal inversion occurs: the winter cooling penalty increases by (+166% in January), while the summer differential paradoxically decreases by 16% as rural temperatures converge with extreme urban baselines. Despite these morphological differences, energy responses exhibit near-identical trajectories (<0.3% variation) under both current and projected climate conditions, indicating that morphological influence on total energy demand remains structurally limited for this controlled building envelope, independently of emission pathway. Carbon analysis confirms a near-perfect convergence where contemporary urban inhabitants (99.70 kgCO₂/m²/year) already experience total building electricity carbon footprints equivalent to future rural conditions under RCP 2.6 (99.10 kgCO₂/m²/year) by 2050. These findings establish that emission pathway selection, not urban design alone, determines infrastructure viability and thermal habitability in semi-arid cities.