Enhancing urban heat island assessment: a comparative study of high resolution bias-corrected UKCP18 climate simulations

Urban Heat Island (UHI) assessments increasingly require high spatial resolution, as nighttime UHI intensities frequently surpass daytime peaks and exacerbate heat-related risks. Existing projections indicate that under a Test Reference Year (TRY) scenario, up to 93% of summer hours by the 2080s could be classified as discomfort hours. It underscores the urgency of accurately modeling future UHI intensities. Concurrently, global climate policies aim to cap warming at 1.5 °C and 2 °C above pre-industrial levels, making it critical to evaluate UHI effects under these thresholds. This study addresses both demands by employing high-resolution (2.2 km) bias-corrected UKCP18 climate simulations to capture nocturnal and monthly temperature variations in urban contexts more effectively than the commonly used 5 km resolution.

We examine diurnal temperature ranges, nighttime minimum temperatures (tasmin), and overall UHI intensities across major UK cities. Uniquely, our analysis applies a bias-correction framework under both 1.5 °C and 2 °C warming scenarios. This approach enables precise alignment of model outputs with observational data and previously documented London UHI benchmarks. By integrating high-resolution observations with the latest climate ensemble projections, this approach offers robust insights into evolving nighttime thermal conditions, which is a critical component of future UHI dynamics. Consequently, the refined understanding of spatiotemporal variability at these warming thresholds provides essential evidence for policymakers, urban planners, and developers. It also facilitates the design of targeted interventions to mitigate escalating nighttime heat stress within rapidly warming urban areas.