Drivers of urban heat in Hong Kong over the past 116 years

Abstract

Understanding how the urban heat island (UHI) effect changes over time and its drivers are essential to efforts in mitigating its impacts through future planning efforts. In Hong Kong, urbanization has occurred for >150 years, but historical analyses of UHI have been limited by the absence of suitable “rural” reference weather observations prior to the 1980's. Here, we used historical maps, meteorological observations from the Hong Kong Observatory, and climate model output from the 20th Century Reanalysis to examine the influence of historical drivers of urban heat from 1884 to 2000. Using the three drivers including total urbanized area, cumulative area of reclaimed land, and a proxy for past urban morphology, we developed linear models of the relationship between urbanization and UHI. Our analysis shows that UHI has a well-correlated positive and statistically significant relationship with all drivers of urban heat in Hong Kong. Historical temperature change in urban Hong Kong (1884–2000) was 0.95 °C, whereas regional climate change over the same period was 0.71 °C. Our results corroborate with historical understanding of Hong Kong's rapid, intensive urban development and furthers understanding on urbanization's effects on local microclimates on a century-long timescale.