IntroductionClimate-related disasters can cause loss of life, disease outbreaks, and medical emergencies1. They also damage infrastructure2; devastate economies3; ruin crops4; diminish economic growth5; and may destabilize governments6,7. In 2023 alone, the Emergency Events Database (EM-DAT) recorded 399 climate-related disasters affecting 93.1 million people, causing over 86,000 fatalities, and resulting in a total of US$202.7 billion in reported economic losses8. Climate extremes are expected to increase in both intensity and frequency9, which raises the question of how the associated disasters will impact societies differently, given their relative level of socioeconomic development.The risk of disaster arising from a hazard is a function of natural and social factors10,11. Climate hazards constitute the physical elements of risk, while societal aspects are represented by population and economic exposure, socioeconomic vulnerability, and response or adaptive capacity. Higher levels of economic and human development generally reduce the risk of adverse impacts from climate-related hazards12,13,14, and the associated fatality tolls are typically lower15. Conversely, people in low-income or low human development countries typically experience more severe impacts from climate-related hazards, such as floods16,17,18,19 and tropical cyclones20.Studies on disaster impacts that consider vulnerability, inequality, and hazard intensity typically rely on national-level indicators or country classifications14,16,17,18,19,21. However, climate-related hazards rarely impact entire countries; they more often affect specific regions, and their impacts depend on local geographic and human factors22. Using national-level indices for subnational events obscures within-country disparities, especially in large nations with internally diverse climates and socioeconomic development. Understanding how local socioeconomic conditions influence the extent to which people are impacted by climate-related hazards is essential23. People living in poverty face reduced access to resources, quality infrastructure, healthcare, and education24. These disparities are captured in the Human Development Index (HDI)25, a composite indicator that measures achievements in health, education, and income. Although the HDI is a commonly reported national statistic, differences in its underlying components (education, health, and income) within one country can be as large as differences between countries26. Recently, subnational Human Development Index (sHDI) data have become available27, enabling global-scale analyses based on regional estimates of socioeconomic vulnerability. Despite these advances, the integration of subnational socioeconomic heterogeneity with global multi-hazard disaster impact assessments remains in its infancy.In this work, we quantify how inequalities in subnational human development influence the impacts of climate-related disasters at the global scale. We analyze a sample of over 7000 climate-related disaster events documented by EM-DAT28 from 1990 to 2020 across 154 countries. We show that lower levels of human development are associated with disproportionately higher human losses and elevated relative economic losses. We further demonstrate that this development-impact gradient persists across most disaster types and hazard intensity levels, and that within-country inequalities amplify disaster risk. These findings provide a global perspective on how inequalities in human development relate to climate-related disaster impacts.ResultsOur analysis of 7061 climate-related disaster events from 1990 to 2020 reveals that floods, storms, and landslides account for 89% of the reported events, causing human and economic losses across regions with diverse socioeconomic conditions on all continents (Fig. 1a and Supplementary Table 1). Disasters associated with cold waves, heat waves, and wildfires are predominantly reported in mid and high latitude regions that tend to exhibit high or very high sHDI. In contrast, drought-related disasters are more frequently reported in low-latitude regions, typically characterized by lower levels of development (low or medium sHDI; see Fig. 1a and Supplementary Table 2). The heterogeneous structure of the EM-DAT sample and the geographic variability of reported impacts are reflected in the number of events and in the mix of disaster types across countries (Supplementary Figs. 1 and 2).Fig. 1: Climate-related disasters and intra-country deviation of human development in impacted regions.The alternative text for this image may have been generated using AI.Full size imagea Locations of climate-related disasters from the EM-DAT colored by sHDI group, shown separately for each disaster type between 1990 and 2020 (total n = 7061; per-type counts indicated in each panel). The four sHDI groups follow the United Nations Development Programme (UNDP) thresholds: low (sHDI