Surface urban heat growth and population exposure across global cities

Urban heat is a significant challenge, arising from the combined effect of global climate change and urban development. Many urban heat studies have been conducted on a city-by-city basis, with a primary focus on summer days. These studies often overlook the broader impact of background climate, seasonality, and diurnal cycle. To address these gaps, we explore Land Surface Temperature (LST) growth in over 1400 cities around the world from 2002 to 2021 using Aqua MODIS satellite. Results show that cities are generally getting warmer across the globe but at different rates. The highest rate of temperature change over the last two decades was found in cold climate cities, with a more rapid increase during winter. These cities are predominantly located in Eastern Europe, extending into parts of Western Asia. However, the lowest rate of change during the day was mostly seen in cities in India and northeastern China. We also quantify the annual rate of change in population exposure to extreme heat across cities, distinguishing the contributions of urban population growth and climate change to exposure trends. These findings provide new insights into identifying regions most vulnerable to global climate change and urban warming, as well as the key factors contributing to these vulnerabilities across the world.