Warming Threatens Urban Vitality

Mobile phone data on 13 million people in Spain—more than a quarter of the population—show that hot days reduce individual mobility, thereby reducing social mixing and making city centers less vibrant. As the climate warms, heat could reshape society, increasing heat-related illness, shifting some physical and outdoor activities to evening and night hours, and altering daily movement patterns. Andrew Renninger and Carmen Cabrera focused on Spain, where heat waves are predicted to become more extensive and intense in the coming decades. Using aggregated, anonymous data from the Spanish Ministry for Transport and Sustainable Mobility, which collects location information via mobile phone usage for 27% of Spanish residents, the authors explored how heat changes movement. The authors find that mobility falls by as much as 10% on hot days and by 20% during hot afternoons. Extreme heat reduces mobility most for the elderly, with no significant gender differences. Lower-income people are less likely than affluent people to reduce mobility, likely because they are unable or unwilling to skip work or work remotely. This socioeconomic effect causes a reduction in social mixing between classes during hot weather. According to the authors, initiatives to install more air conditioning may help people endure heat, but they may not sustain urban dynamism, as people increasingly stay isolated inside during hot weather. Greening and shading of urban cores could help keep them livable and attractive as the climate warms.