The Growing Threat of Global Urban Heat Island Effects in Lower-Middle- and Low-Income Countries

Abstract Urbanization has undergone significant growth in recent decades, but we still lack information regarding the disparity caused by the urban heat island (UHI) effect associated with urban development. Upon analyzing 4,832,660 urban grids worldwide from 2003 to 2018, we found that there is an uneven distribution in the growth of surface urban heat island intensity (SUHII) across countries in four distinct economic levels. The SUHII gradually decreased after 2006 and 2004 in high and upper-middle income groups, respectively. However, increasing trend was observed in the low and lower-middle income groups. Specifically, during the daytime, 27% of low-income regions exhibit a largest-scale net increasing trend, while the lower-middle-income group has the largest area (19.10%) with a net increasing trend during the nighttime. The growth rate of SUHII in high- and upper-middle-income country urban areas is close to the average urbanization level of these countries, but the growth rate of SUHII in lower-middle- and low-income country cities is much faster. Our findings highlight that urban areas in lower-middle- and low-income countries face more urgent UHI issues and require targeted interventions for mitigation. High- and upper-middle-income countries need shoulder greater responsibility in mitigating the UHI effects by offering technical expertise and guidance to economically disadvantaged nations.