Urban expansion, diurnal land-surface temperature, and population exposure to hot surfaces across Iraq, 2000–2020

Abstract

Iraq is pursuing urban and economic development while facing intensifying heat, water stress, and climate vulnerability. Yet national evidence that jointly tracks urban expansion, daytime and nighttime surface-temperature dynamics, settlement context, and population exposure remains limited. This study integrates Global Human Settlement Layer built-up, population, and settlement datasets with MODIS Terra land-surface temperature (LST) data to assess changes across Iraq from 2000 to 2020. Built-up surface increased by 495.8 km², with the largest absolute additions occurring in Erbil (57.1 km²), Sulaymaniyah (52.4 km²), and Baghdad (47.9 km²). The framework separately evaluates daytime and nighttime summer LST, compares recent thermal conditions among settlement classes, and identifies residents in populated cells at or above the national 90th percentile of recent LST. The results indicate a weak national daytime warming trend (+0.35 °C decade⁻¹; p = 0.401) and a stronger nighttime trend (+0.75 °C decade⁻¹; p < 0.001), alongside substantially greater population exposure to high nighttime than daytime temperatures. Overall, the study provides a transparent and reproducible national framework for identifying where urban development, diurnal surface warming, and population exposure coincide, thereby supporting spatially targeted climate adaptation and sustainable urban planning in Iraq.