Increasing Hourly Population Exposure to Moderate Cold Under Climate Warming

Abstract Although the human health risk from cold stress may be greater than from heat stress, population cold exposure has received little attention compared to heat exposure in the context of climate warming. A particular puzzle is that while the number of cold days has markedly decreased under climate warming, the cold-related influenza positivity rate has substantially increased. Here we reveal global hourly population exposure for different cold categories based on observations and climate model simulations from 1979 to 2100, and explore the potential link between population cold exposure and influenza positivity rate. Our results show that the number of cold hours did not decrease uniformly across all categories under climate warming, but shifted from extreme cold to moderate cold. Global hourly population cold exposure increased substantially from 1979 to 2023 (2.05 × 10 10 person-hours yr −1 ), and this trend is expected to persist in the near term with continued population growth. The number of influenza positives and the influenza positivity rate were significantly correlated with hourly population cold exposure. These findings imply a current risk of population cold exposure and emphasize the need for increased attention to this risk.