Surface urban heat island effects intensify more rapidly in lower income countries

As urbanization proceeds globally in recent decades, a nuanced understanding of the differential impacts of the urban heat island (UHI) effect across income country groups is crucial. Through an analysis of ~5 million urban grids from 2003 to 2018, we discovered that the average surface urban heat island intensity (SUHII) increased at a rate of 0.021 °C annually. Despite the extensive areas of SUHII increase in higher-income countries, particularly the US and China, it is the low and lower-middle-income countries that exhibited a more pronounced net increase in intensity. Specifically, 27% of urban grids in low-income countries witnessed the most substantial net increase during the daytime, while 19% of urban grids in lower-middle-income countries led the surge at nighttime. Higher-income countries’ SUHII growth reflects their pace of urbanization, but the trend of intensifying urban heat expands faster in lower-income economies. Such findings underscore an impending UHI challenge for lower-middle and low-income nations, emphasizing the need for targeted mitigation and adaptation strategies.