Exposure to dangerous levels of heat and humidity in cities across the world has exploded over the past three decades, according to new research. In a study of more than 13,000 cities, the number of people exposed to extremely hot and humid days in a given year (measured in “person-days”) tripled between 1983 and 2016.
It’s a symptom of two trends colliding: urban population growth and rising global average temperatures. Cities often reach higher temperatures than surrounding rural areas because they’re typically designed in a way that traps heat. So when people flock to urban centers, they’re also flocking to places where they could be at greater risk of heat-related illness and…