Regional variation in the role of humidity on city-level heat-related mortality

The rising humid heat is regarded as a severe threat to human survivability, but the proper integration of humid heat into heat-health alerts is still being explored. Using state-of-the-art epidemiological and climatological datasets, we examined the association between multiple heat stress indicators (HSIs) and daily human mortality in 739 cities worldwide. Notable differences were observed in the long-term trends and timing of heat events detected by HSIs. Air temperature (Tair) predicts heat-related mortality well in cities with a robust negative Tair-relative humidity correlation (CT-RH). However, in cities with near-zero or weak positive CT-RH, HSIs considering humidity provide enhanced predictive power compared to Tair. Furthermore, the magnitude and timing of heat-related mortality measured by HSIs could differ largely from those associated with Tair in many cities. Our findings provide important insights into specific regions where humans are vulnerable to humid heat and can facilitate the further enhancement of heat-health alert systems.

Significance Statement: Climate change has intensified the frequency, duration, and severity of lethal heat stress in recent years, a trend expected to exacerbate further. Despite the increasing focus on humid heat, there remains a gap in understanding how to effectively integrate humid heat into heat-health alert systems across regions with diverse climatic conditions. Addressing this gap, our study utilizes extensive epidemiological and climatological datasets to discern locations where incorporating humidity largely improves the predictive capacity for heat-related mortality compared to relying solely on air temperature. These findings offer crucial insights for enhancing heat-health alert systems in the face of ongoing climate change.

Description

MCC Collaborative Research Network Authors - INSA: Joana Madureira (Environmental Health Department, National Institute of Health, Porto, Portugal); Susana das Neves Pereira da Silva (Department of Epidemiology, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisbon, Portugal).

Keywords

Climate Change Humidity Heat Stress Urban Climate Mortality MCC Collaborative Research Network Multi-Country Multi-City Estados de Saúde e de Doença Determinantes da Saúde e da Doença Avaliação do Risco