Escaping Environmental Hazards? Human Mobility in Response to Air Pollution and Extreme Cold Events

Understanding the patterns of human mobility and how they relate to different environmental risks is key to developing effective adaptation strategies. To this end, this study applied large-scale mobile phone data to examine the differential mobility responses to and interaction between air pollution and extreme cold events and attempted to identify nonlinearities in the relationship between short-term movements and the two environmental hazards. The results revealed that extreme cold events had a strong influence on the mobility decisions of residents in the city of Chengdu, China. Residents were more likely to react to climate-related hazards in their daily mobility than air pollution, which is often characterized as a slow-onset, small-impact, and frequent concern. The findings from the estimation of an interaction term indicated an antagonistic effect; that is, the combined effect of air pollution and extreme cold events on short-term movements was significantly lower than expected from the sum of their individual effects. Using a piecewise regression approach, this study uncovered nonlinearities in mobility as a response to air pollution and cold events as the number of trips from hazardous places to less hazardous places increased more than proportional to the differentials in air quality and magnitude of cold events.