How much has urbanisation affected United Kingdom temperatures?

Ian L M Goddard,Simon F B Tett

doi:10.1002/asl.896

Abstract

This study aims to estimate the affect of urbanisation on daily maximum and minimum temperatures in the United Kingdom. Urban fractions were calculated for 10 km × 10 km areas surrounding meteorological weather stations. Using robust regression a linear relationship between urban fraction and temperature difference between station measurements and ERA‐Interim reanalysis temperatures was estimated. For an urban fraction of 1.0, the daily minimum 2‐m temperature was estimated to increase by 1.90 ± 0.88 K while the daily maximum temperature was not significantly affected by urbanisation. This result was then applied to the whole United Kingdom with a maximum T min urban heat island intensity (UHII) of about 1.7K in London and with many UK cities having T min UHIIs above one degree.This paper finds through the method of observation minus reanalysis that urbanisation has significantly increased the daily minimum 2‐m temperature in the United Kingdom by up to 1.70 K.

Highlights

The urban heat island intensity (UHII), which describes increased temperatures in urban areas, has long been known and attempts have been made to quantify it for many years (Mitchell, 1961; Oke, 1982)
This study aims to deal with the problem of park cool island (PCI) mitigation of the UHI and the issues of urban/rural classification by determining the degree of urbanisation of a given weather station, rather than having discrete classes
The results suggest that urbanisation has had no significant impact on daily maximum temperature across most of the annual cycle

Summary

Introduction

The urban heat island intensity (UHII), which describes increased temperatures in urban areas, has long been known and attempts have been made to quantify it for many years (Mitchell, 1961; Oke, 1982). The urban heat island (UHI) develops through changes to the surface energy balance due to anthropogenic modifications to the land surface. The importance of understanding how these changes will affect the global climate and the potential bias to land temperature records arising from urbanisation has piqued interest in this area of research. Due to the consequences of increasing temperatures in urban areas, such as increasing air pollution and mortality rates (Johnson et al, 2005; Stedman, 2004), many studies have attempted to quantify how temperatures in highly urbanised areas will be affected by increasing urbanisation.

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