Heat increases experienced racial segregation in the United States

Segregation on the basis of ethnic groups stands as a pervasive and persistent social challenge in many cities across the globe. Public spaces provide opportunities for diverse encounters but recent research suggests individuals adjust their time spent in such places to cope with extreme temperatures. We evaluate to what extent such adaptation affects racial segregation and thus shed light on a yet unexplored channel through which global warming might affect social welfare. We use large-scale foot traffic data for millions of places in 315 US cities between 2018 and 2020 to estimate an index of experienced isolation in daily visits between whites and other ethnic groups. We find that heat increases segregation. Results from panel regressions imply that a week with temperatures above 33{\deg}C in a city like Los Angeles induces an upward shift of visit isolation by 0.7 percentage points, which equals about 14% of the difference in the isolation index of Los Angeles to the more segregated city of Atlanta. The segregation-increasing effect is particularly strong for individuals living in lower-income areas and at places associated with leisure activities. Combining our estimates with climate model projections, we find that stringent mitigation policy can have significant co-benefits in terms of cushioning increases in racial segregation in the future.