Global urban climatology: a meta-analysis of air temperature trends (1960\u20132009)

Alvin C G Varquez,Manabu Kanda

doi:10.1038/s41612-018-0042-8

Alvin C G Varquez, Manabu Kanda

Open Access

https://doi.org/10.1038/s41612-018-0042-8

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Abstract

Air temperature trends (1960–2009) based on stations in cities, minus those based on global surface temperature datasets, are defined herein as urban heat island (UHI) trends. Urban climate was examined globally by comparing UHI trends with indices of geophysical factors, including background climate, latitude, and diurnal temperature range (DTR) and indices of artificial factors, including anthropogenic heat emission (AHE) and population indices. Surprisingly, a better relationship was found between UHI trends and DTR—an integrated geophysical index representing thermal inertia—than with the indices of artificial factors. Thus, while an increase in sensible heat (mechanism 1) triggers UHI formation, this study infers that large thermal inertia (mechanism 2) contributes significantly on UHI. The correlation of UHI trends with other indices can be explained by both mechanisms.

Highlights

Local climate modifications caused by urbanisation and global climate change can lead to unfavourable environmental conditions such as poor air ventilation, urban warming, flash floods, and health-related issues such as heat stroke and water/air-borne diseases
UHI is generally estimated from the spatial difference between urban and rural temperatures
In this study, UHIs were estimated using the trends of long-term temperature records.[15]

Summary

Introduction

Local climate modifications caused by urbanisation and global climate change can lead to unfavourable environmental conditions such as poor air ventilation, urban warming, flash floods, and health-related issues such as heat stroke and water/air-borne diseases. In the recent Intergovernmental Panel on Climate Change Fifth Assessment Report, it was predicted that an increasing percentage of the world’s population will be exposed to the direct impacts of climate change in urban areas. A recent study found the accumulated total costs resulting from the impact of global and local climate change on all cities since 2000 were about 2.6 times the costs without urban-weather-related effects.[1] It is necessary to separate and quantify the effects of urbanisation and global climate change on warming in cities and explain differences in the mechanisms underlying the two factors. There is a wide gap between urban climate and global climate change studies

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