Cumulative Intersection Risks of Aging and Climate Vulnerability: A Spatiotemporal Analysis Based on Global Public Databases

Abstract

Global population aging and climate change are creating mutually reinforcing, intersecting cumulative risks, yet their nonlinear amplification mechanisms have not been systematically quantified. This study integrates open data sources, including the World Bank World Development Indicators (WDI), Lancet Countdown, NASA Goddard Institute for Space Studies (GISS), and the International Disaster Database (EM-DAT). Taking 30 sample countries from 1990 to 2023 as research subjects, it constructs the Intersecting Cumulative Risk Index (ICRI) and conducts spatiotemporal overlay analysis on the rates of population aging and temperature anomalies. The heat-related mortality data adopted in this research are derived from model estimations of the Global Burden of Disease (GBD), rather than raw statistics from national vital registration systems; all analyses are performed based on such modeled data, and relevant inferences should be interpreted within this epistemological framework. The study's findings are as follows: (1) The proportion of the global population aged 65 and above keeps rising, with East Asian economies such as China and Japan experiencing far faster aging than high-income countries in comparable historical periods; (2) Heat-related mortality rises nonlinearly. Globally, heat deaths among people aged 65 and older in 2023 increased by approximately 167% compared with the 1990s. If only demographic shifts are considered (under the assumption of constant climatic conditions), around 65 percentage points of the growth can be attributed to population aging. The remaining excess growth of roughly 102 percentage points is provisionally estimated as the net effect of climate change superimposed on population aging—this decomposition is derived from the Lancet Countdown's modelled counterfactuals and should be interpreted as a structural breakdown rather than an independently identified causal attribution—this net effect covers both direct physiological impacts of rising temperatures and the intersecting cumulative amplification of aging and warming; (3) Countries with low Human Development Index (HDI) scores feature relatively mild population aging yet severe adaptation deficits. Disparities in air conditioning penetration lead to a 19-fold gap in the ratio of air conditioning-preventable deaths, generating institutional intersecting vulnerability; (4) Dimensions including gender, urban-rural divides, and living arrangements further amplify heterogeneous risks among elderly populations. This research suggests that population aging and climate vulnerability are not merely additive but may be mutually reinforced through three pathways: physiological-climatic coupling, socio-spatial accumulation, and economic-institutional accumulation. It provides empirical evidence for incorporating an elderly justice perspective into climate adaptation policies.