Wet-bulb temperatures reveal inequitable heat risk following climate change in Hong Kong

Rising temperatures will impact urban communities, which are growing as a proportion of the global population. However, the effects of increasing temperature may not be felt equally, with less wealthy neighbourhoods experiencing hotter thermal environments in some urban areas because of geographic location and tree cover. While relationships have been drawn between wealth inequality and temperature in urban areas, these rarely project into the future or combine humidity and air temperatures into 'wet-bulb temperature' at fine spatial resolution, which is more directly relevant to the human experienced environment. Here I present an analysis of present and future wet-bulb temperatures in Hong Kong, an economically developed subtropical city in South-East Asia. I couple census data with recently available 30 x 30 m resolution climate models to examine how the income of districts and their physical characteristics are correlated with human-experienced local temperatures. I uncover evidence of thermal inequity, with wealthier districts exhibiting cooler conditions than less wealthy districts. Projecting into the future using three different climate change scenarios I demonstrate that wet-bulb temperatures considered dangerous to human survival may be commonly experienced in Hong Kong by the end of the century. However, the wealthiest districts of Hong Kong are likely to have a thermal safety margin of at least 25-30 years more than the least wealthy districts before these dangerous temperatures are reached. Due to the high population density and economic importance of the region, these findings have significant implications for public health and urban planning as global temperatures continue to rise.