The Climate-Health Divide: How Climate Change Will Rewire Health Care Across High-, Middle-, and Low-Income Settings

Background: Climate change is increasingly recognised not only as an environmental emergency but also as a structural determinant of health and health-system performance. Its clinical consequences will not be distributed evenly: high-income countries face rising heat mortality, infrastructure fragility, ageing-related vulnerability, and the need to decarbonise technologically intensive care; middle- and low-income countries face heterogeneous but often more compressed combinations of heat, infectious disease, food insecurity, water stress, displacement, conflict-related fragility, and limited fiscal capacity. Objective: This structured narrative review proposes a comparative framework for understanding how climate change will transform health care across high-, middle-, and low-income settings and identifies adaptation priorities that are resilient, equitable, and low-carbon. Methods: We synthesised major climate-health assessments, peer-reviewed epidemiological studies, modelling papers, systematic and scoping reviews, and health-system decarbonisation literature identified through targeted searches and reference chaining. Five climate-health pathways, specified a priori from established direct, indirect, and socially mediated pathway frameworks, were used to organise the review. Findings: Climate change will reshape health care through five interacting pathways: direct thermal injury and extreme-weather mortality; altered infectious disease ecology; food, water, and nutritional insecurity; mental, maternal-child, and occupational impacts; and damage to the infrastructure, workforce, supply chains, finances, and emissions profile of health systems. In high-income countries, climate stress exposes the limits of hospital-centred, carbon-intensive, just-in-time care. In middle-income countries, expanding coverage and technology coexist with uneven insurance, large informal workforces, and rapidly growing emissions. In low-income and fragile settings, the same hazards interact with undernutrition, weak surveillance, under-resourced primary care, and constrained finance to produce larger marginal health losses. Conclusions: The central contribution is the concept of the climate-health divide: the unequal conversion of shared climate hazards into clinical demand, service disruption, financial stress, and emissions-intensive responses. Climate resilience and healthcare decarbonisation should therefore be designed together rather than treated as separate agendas.