The scientific community has established a clear connection between the planet’s changing climate and increasing human mortality. Researchers are investigating the numerous direct and indirect pathways through which climate change results in loss of life. Understanding these mechanisms reveals a multifaceted global health challenge.
Direct Health Impacts from Extreme Weather and Temperature
Climate change causes death through the increased frequency and intensity of extreme weather events. Heatwaves are becoming more common and severe, leading to a surge in heat-related fatalities. During these events, the body’s core temperature can rise to dangerous levels, causing heatstroke. This condition, where the body’s temperature regulation system fails, can lead to organ damage and death.
Extreme heat also places strain on the cardiovascular system. The body works harder to cool itself by pumping more blood to the skin, which can be overwhelming for individuals with pre-existing heart conditions. This stress can trigger fatal heart attacks and strokes. Research attributes 37% of heat-related deaths to human-induced climate change, with fatalities among those over 65 rising by 70% in two decades.
Severe storms like hurricanes and cyclones, intensified by a warming climate, are another direct cause of mortality. Drowning is a primary cause of death during these events, as storm surges and extreme rainfall lead to widespread flooding. The force of these storms also generates flying debris and causes building collapses, resulting in physical trauma. Downed power lines in flooded areas create electrocution hazards.
Wildfires, fueled by hotter and drier conditions, are also a direct threat to human life. The most immediate dangers are severe burns and smoke inhalation, which can cause asphyxiation. The smoke from these fires contains a mix of particulate matter and gases that can be deadly, especially for those with respiratory conditions. The chaos of evacuations can also lead to fatal accidents.
Indirect Health Consequences
The health impacts of climate change extend beyond immediate weather disasters, creating consequences that increase mortality over time. Worsening air quality is a major contributor, as higher temperatures accelerate the formation of ground-level ozone, a harmful air pollutant. This, combined with increased particulate matter from fossil fuels and wildfires, leads to a higher incidence of chronic respiratory and cardiovascular diseases.
This long-term exposure to polluted air exacerbates conditions like asthma and chronic obstructive pulmonary disease (COPD), leading to more frequent and severe attacks that can be fatal. The fine particulate matter, known as PM2.5, is dangerous as it can penetrate deep into the lungs and enter the bloodstream. This infiltration contributes to the development of heart disease, stroke, and lung cancer.
Rising global temperatures and altered rainfall patterns are also expanding the geographic range of disease-carrying vectors like mosquitoes and ticks. As temperatures warm, these vectors can survive and reproduce in regions that were previously too cold. This expansion is leading to an increase in deaths from vector-borne illnesses that were once confined to specific tropical and subtropical areas.
Diseases such as malaria and dengue fever, transmitted by mosquitoes, are now appearing at higher elevations and latitudes. Ticks carrying Lyme disease and other pathogens are also expanding their habitats. The introduction of these diseases into new regions means that local populations and healthcare systems are often ill-equipped to diagnose and treat them, leading to higher mortality rates than in areas where the diseases are endemic.
Impacts on Food and Water Systems
Climate change threatens the systems that provide food and water, leading to loss of life through malnutrition and disease. Shifting weather patterns, including prolonged droughts and erratic rainfall, directly impact agricultural productivity. These changes cause widespread crop failures and reduce livestock viability, diminishing food supplies and leading to food insecurity.
This decline in agricultural output results in malnutrition, a primary driver of mortality, especially in children. Chronic hunger weakens the immune system, making individuals more susceptible to deadly infectious diseases. In severe cases, the complete collapse of local food systems leads to famine and starvation. In 2020, 98 million more people experienced food insecurity compared to the average from 1981–2010.
The availability and safety of drinking water are also compromised by climate change. Extended droughts deplete rivers, lakes, and groundwater reserves, leading to water scarcity. In these conditions, people may rely on unsafe water sources or suffer from fatal dehydration.
Increased rainfall intensity and flooding can overwhelm sanitation systems and contaminate water supplies with pathogens. This contamination leads to outbreaks of waterborne diseases like cholera, dysentery, and typhoid fever. These illnesses cause severe diarrhea and dehydration and can be deadly, particularly in areas with limited medical care. The World Health Organization expects that between 2030 and 2050, climate change will cause approximately 250,000 additional deaths per year from these combined factors.
Vulnerable Populations and Disproportionate Risks
While climate change is a global phenomenon, its deadliest impacts are not distributed equally. Certain populations face a higher risk of death due to a combination of geographic, demographic, and socioeconomic factors. These groups are more susceptible to the previously outlined health threats because of an intersection of multiple risk factors.
Geographic location is a primary determinant of risk. Communities in low-lying coastal areas face mortality from sea-level rise and more intense storm surges. People living in arid or semi-arid regions are vulnerable to death from heat stress and malnutrition caused by drought. In the Arctic, melting ice and changing ecosystems disrupt traditional food sources, threatening the survival of Indigenous populations.
Demographic characteristics also play a role in susceptibility. The elderly are more physiologically vulnerable to extreme heat and have a higher prevalence of pre-existing conditions like heart and lung disease. Infants and young children have developing immune systems and are more susceptible to malnutrition and diarrheal diseases. Pregnant women also face heightened risks.
Socioeconomic status is a multiplier of risk. Individuals living in poverty often lack access to robust housing, healthcare, and critical infrastructure like air conditioning, making them more vulnerable during extreme weather events. Outdoor workers, such as farmers and construction laborers, have a much higher exposure to extreme heat and air pollution. This lack of resources and greater exposure means the world’s most disadvantaged communities bear the heaviest burden of climate-related mortality.