Recent urbanization increases exposure to humid-heat extreme events over populated regions of China

Abstract

Extreme-heat research has largely focused on dry heat, while humid heat, which presents a major societal impact, especially on human health, remains relatively understudied. Previous studies have revealed that a wet-bulb temperature (TW) of 35 °C marks our upper physiological limit, and much lower values also have serious health impacts. Our evaluations from observations showed that the daily maximum TW values over China have been scarcely reported above 35 °C, but humid-heat extreme days of TW above 30 °C have been reported each year during the past four decades, being mainly centered over the highly populated regions, including East China, South China, and the Sichuan basin. Further analyses indicated that the recent rapid urbanization process in China has amplified the societal impacts of humid-heat extremes, and land exposure to humid heat over urban regions is expected to increase at a faster rate than other regions of China. This suggests increasing risks of humid-heat extremes on human health in big cities of densely populated regions due to rapid urbanization. As indicated here, the population of China has become increasingly exposed to such extremes, with a strong increasing tendency of about 3100 persons per day per year since 2000.

摘要

目前对于高温的研究主要侧重于干热, 针对湿热的研究相对较少, 但它通常会造成更大的社会影响, 尤其对人体健康的威胁. 已有研究证实, 当环境湿球温度超过35 °C时, 它会破坏人体正常生理代谢, 进而威胁人体健康. 本研究指出在过去四十年, 中国区域日最高湿球温度几乎没有超过35 °C, 但部分地区日最高湿球温度超过了30 °C, 主要集中在中国的人口密集区, 包括华东, 华南和四川盆地等. 进一步分析发现, 中国区域近期的快速城市化加剧了极端湿热事件的社会影响, 城市地区暴露于极端湿热事件的范围的增加速率明显大于其他地区, 这也意味着快速城市化使得人口密集区暴露于极端湿热事件的风险明显增加. 初步估算指出, 自2000年以来, 中国区域暴露于极端湿热事件的人口数以每年每天约3100人次的速率显著增加.