UK Climate Projections: Summer daytime and night-time urban heat island changes in England’s major cities

Y. T. Eunice Lo, Daniel M. Mitchell, Sylvia I. Bohnenstengel, Mat Collins, Ed Hawkins, Gabi Hegerl, Manoj Joshi, Peter A. Stott

Research output: Contribution to journalArticlepeer-review

Abstract

In the UK where 90% of residents are projected to live in urban areas by 2050, projecting changes in urban heat islands (UHIs) is essential to municipal adaptation. Increased summer temperatures are linked to increased mortality. Using the new regional UK Climate Projections, UKCP18-regional, we estimate the 1981–2079 trends in summer urban and rural near-surface air temperatures, and UHI intensities during day and at night in the 10 most populous built-up areas in England. Summer temperatures increase by 0.45–0.81°C per decade under RCP8.5, depending on the time of day and location. Night-time temperatures increase more in urban than rural areas, enhancing the night-time UHI by 0.01–0.05°C per decade in all cities. When these upward UHI signals emerge from 2008–2018 variability, positive summer night-time UHI intensities of up to 1.8°C are projected in most cities. However, we can prevent most of these upward night-time UHI signals from emerging by stabilising climate to the Paris Agreement target of 2°C above pre-industrial levels. In contrast, daytime UHI intensities decrease in nine cities, at rates between -0.004 and -0.05°C per decade, indicating a trend towards a reduced daytime UHI effect. These changes reflect different feedbacks over urban and rural areas and are specific to UKCP18-regional. Future research is important to better understand the drivers of these UHI intensity changes.
Original languageEnglish
JournalJournal of Climate
DOIs
Publication statusPublished - 4 Aug 2020

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