Small Tropical Islands Also Exposed to Extreme Humid Heat by the End of the Century

Abstract Extreme humid heat is projected to increase markedly by the end of the century, particularly in the tropics. Yet, the case of small islands is ambiguous because the available studies are based on coarse global climate models (GCMs) that ignore them. Here, bias‐corrected GCMs at weather station sites are used to assess present and future extreme humid heat conditions on various tropical islands. Levels of humid heat are estimated with the Heat Index (HI) combining temperature and humidity. Extreme humid heat intensity is projected to reach particularly dangerous levels by the end of the century, with higher HI values for islands located closer to the equator. Longer humid heatwaves are also notably projected to increase in frequency, with more pronounced increases equatorward, because of the lower seasonal variability of HI. Such severe conditions threaten the lives of millions of island inhabitants across the tropics.