Devastating Health Impacts of Climate Change: 7 Critical Threats Destroying Lives in 2025

Rising temperatures and extreme events are reshaping risks to human well-being. Heatwaves, floods, storms and wildfires now come more often and hit harder. These trends matter for people, health systems, and the services communities rely on.

Billions already live in high-risk zones. Studies show vast populations face greater exposure to heat and air pollution, while water and food systems grow more fragile. By the 2030s, experts expect thousands of additional deaths each year from undernutrition, infectious disease and heat stress.

Low-income countries and parts of South Asia bear the heaviest burden despite low emissions. This unequal toll threatens progress toward universal care as shocks disrupt clinics, raise costs, and strain staff.

This report sets a future-focused agenda: it maps current signals, explains pathways that link environmental shifts to illness, highlights unequal burdens with an India lens, and points to policy and health-system actions to 2030 that can cut emissions and improve air quality and well-being.

Key Takeaways – Health Impacts of Climate Change

• Extreme weather and poor air quality are already increasing risks to people and public health.
• Billions live in high-exposure areas; projected additional deaths highlight urgency.
• Low-income regions, including many in India, face the worst outcomes despite low emissions.
• Health systems must adapt to withstand shocks and protect care delivery.
• Decisive policies can reduce emissions while improving air quality and economic outcomes.

Executive Overview: What the next decade means for human health

The coming decade will bring hotter summers, thicker smoke, and more frequent hazards that raise risks for people everywhere.

Ten of fifteen key indicators hit record levels in 2024, and recent data show people endured about 46 extra days of dangerous heat each year from 2019–2023. Older adults bore the brunt: heat-related deaths for those 65+ rose by 167% versus late 20th-century baselines.

Air quality and emissions remain a dual threat. Fossil-fuel PM2.5 contributed roughly 2.09 million of the 6.4 million PM2.5 deaths in 2021. Nearly all regions breathe unsafe air, with 90% of premature air-pollution deaths concentrated in low- and middle-income countries.

Water stress and drought widened threats to food supplies. Almost half of global land experienced at least one month of extreme drought in 2023, helping drive 151 million more people into food insecurity in 2022.

Health systems face rising caseloads from heart and lung disease, injuries, and climate-sensitive infections while coping with strained infrastructure.

• Near-term choices matter: faster decarbonization and targeted resilience can cut deaths and hospital visits.
• Immediate wins: early warnings, heat-action plans, and climate-informed surveillance save lives now.
• Equity first: developing countries need finance and tech transfer to reduce unequal harms.

The current trajectory of climate-health risks: Signals from today shaping tomorrow

Signals from recent years point to longer heat seasons, worse smoke episodes, and shifting disease zones. These trends already reshape risks for cities and rural districts across India.

Extreme heat and older adults

Prolonged heatwaves are amplifying illness and deaths. People experienced an average of 46 extra dangerous heat days between 2019–2023. Heat-related mortality for adults 65+ rose 167% versus 1990–1999.

Urban heat islands, crowded housing, and outdoor work make older adults and informal workers especially vulnerable.

Air pollution and fossil fuels

Fossil-fuel PM2.5 caused about 2.09 million of 6.4 million PM2.5 deaths in 2021.

This dual problem — warming plus pollution — drives more cardiopulmonary disease and premature deaths, while also raising local temperatures.

• Wildfires and smoke: fire danger rose in 124 countries, and short-term PM2.5 spikes worsen asthma, COPD, and cardiac events.
• Drought and food: nearly half of land faced extreme drought in 2023; an extra 151 million people faced food insecurity in 2022.
• Vector shifts: dengue and malaria suitability expanded, lengthening transmission seasons for Aedes and Anopheles mosquitoes.

These indicators are at record levels. Faster surveillance, targeted heat alerts, and clean-energy moves can cut pollution and save lives.

Climate change: Its impact on health — direct, indirect, and cascading effects

More frequent hazards are creating chains of harm that reach hospitals, homes, and livelihoods.

From storms to floods: Intense storms and river floods cause trauma, drowning, and damage to clinics. They interrupt emergency care, cold chains, and medicine supplies, raising short-term mortality and long-term service gaps.

Heat stress and noncommunicable disease risks

Severe heat waves raise the risk of heart attacks, strokes, kidney injury, and worsened lung disease. Urban heat islands amplify these effects, sending more older adults and outdoor workers to emergency wards.

Mental health and psychosocial harm

Acute disaster trauma and chronic anxiety from repeated shocks increase depression and PTSD. Displacement and lost livelihoods deepen stress and reduce access to mental health support.

Water, inequality, and service continuity

Floodwaters contaminate drinking sources while droughts concentrate pollutants. Low-income families face higher out-of-pocket costs and greater barriers to care as services are disrupted.

Pathway	Direct effect	Service risk	Local example (India)
Storms & floods	Injury, drowning	Hospital damage, supply breaks	Coastal cyclone floods strain district hospitals
Heat waves	Cardiac, renal events	Surge in admissions, power loss	Plains heatwaves raise dehydration cases
Water shocks	Diarrheal disease rise	Contaminated water supplies	River-basin floods contaminate wells
Mental health	PTSD, anxiety	Interrupted counseling services	Post-disaster trauma clinics overwhelmed

• Resilience matters: backup power, flood-proof design, and evacuation planning keep care running.
• Community cooling centers, continuity plans for chronic patients, and inclusive social protection cut risks.
• Integrated risk assessments should guide local health planning and resource allocation.

Unequal burdens and India’s public health resilience in a warming world

Across India, families in informal settlements face far higher exposure to extreme heat, smoke, and flood risk than wealthier neighborhoods.

Vulnerable groups

Who is most at risk

Women, children, older adults, people with disabilities, and outdoor workers carry layered risks. Poor housing, limited cooling, and low access to care make outcomes worse.

Workforce and maternal risks

Informal and outdoor workers lack paid leave, cooling, and protective gear. Pregnant women and young children face higher odds of malnutrition, vector illnesses, and disrupted immunization after storms.

Priority investments for India

Key actions include heat and flood early warning, climate‑informed primary care protocols, and last‑mile messages in local languages.

• Integrate weather with disease surveillance and digitize registries.
• Climate‑proof PHCs and district hospitals with reliable power (including solar) and safe water.
• Train ASHAs and frontline workers for outreach, hydration advice, and referrals.

Targeting matters: map hotspots — slums, cyclone belts, and drought zones — to focus resources where they save the most lives. Partnering with UNDP and WHO initiatives helps scale resilient, low‑emission health systems across vulnerable regions and countries.

From risk to resilience: Health systems, emissions, and the path to low-carbon care

Health systems must cut their own emissions while boosting resilience to protect patients and staff. The sector now accounts for about 4.6% of global greenhouse gas emissions and rose 36% from 2016–2021. That footprint also drives air pollution and lost healthy life years.

The healthcare footprint: 4.6% of global emissions and rising

Facility operations, supply chains, and transport together create a sizeable carbon burden. In 2021, related pollution cost roughly 4.6 million DALYs globally.

Scopes 1–3: Where sector emissions come from

Scope 1 covers direct on-site fuels and anesthetic gases. Scope 2 covers purchased electricity and cooling. Scope 3 covers procurement, logistics, and waste. In India, big levers are facility energy use, cold chains, and procurement.

Decarbonizing care: energy efficiency, renewables, and low-carbon supply chains

Quick wins include energy audits, LED retrofits, efficient HVAC, and solar-plus-storage for critical loads. Tackling supply chains and switching high‑carbon anesthetics reduces emissions and pollution near hospitals.

Global initiatives and lessons for India

WHO’s ATACH and the NHS net‑zero program show practical steps: governance, supplier engagement, and tracking. Adapting these approaches can lower operating costs, cut emissions, and strengthen service continuity across Indian facilities.

Policy pathways to 2030: Integrating health into climate action

Embedding measurable health outcomes into national commitments will unlock finance and strengthen accountability. At COP28, 148 governments endorsed the Declaration on Climate and Health, yet only 32% of current NDCs mention the health sector. India can lead by adding clear targets for avoided hospitalizations, reduced emissions near facilities, and improved access to care in heat and flood events.

Embedding health in NDCs and adaptation plans

Governments should include health‑inclusive emissions targets, heat‑health action plans, and clean cooking and transport strategies within national and state plans. Measurable indicators—such as reduced outdoor-pollution exposures and emergency response times—help track progress and attract GCF and GEF funds.

Climate‑informed disease surveillance and early warning

Integrate meteorological data with health reporting. Digitize case reporting, expand lab networks, and enable real‑time alerts for heat, floods, air quality, and vectors. Interoperable systems should trigger hospital surge protocols and community outreach for high‑risk groups.

Financing adaptation and protecting vulnerable communities

Leverage MDBs and adaptation funds to finance resilient facilities, solar backup energy, and safe water systems. Deploy social protection to cushion shocks for low‑income households and support state and city pilots that scale successful models nationally.

• Co‑design policies with frontline workers, women’s groups, and disability advocates.
• Report annually on climate‑health indicators, investment flows, and avoided deaths.
• Use WHO’s ATACH and UNDP support to fast‑track implementation and workforce training.

Conclusion

Act now, protecting human health this decade requires rapid emissions cuts paired with scaled resilience that shields communities and services.

Evidence shows decarbonization and practical resilience steps deliver cleaner air, fewer deaths, and lower costs. For India, priorities include heat‑health preparedness, clean‑air action, safe water access, food and nutrition security, and climate‑ready care at every level.

Focus equity: direct resources to the most exposed people and ensure access to care and social protection. Measure exposure, avoided hospitalizations, and resilience gains to guide investment.

Align ministries, states, cities, and communities—and partner with WHO, UNDP, and ATACH—to turn near‑term wins into lasting climate‑health security.

FAQ

What are the main ways a warming planet affects human well-being?

Rising temperatures increase heat-related illness and worsen heart and lung disease. More frequent storms and floods cause injuries, displace communities, and disrupt health services. Shifts in rainfall and drought drive food and water insecurity, raising malnutrition risk. Air pollution from fossil fuels and wildfires worsens respiratory disease and contributes to millions of premature deaths worldwide.

Which groups face the greatest risks from environmental shifts?

Older adults, young children, pregnant people, outdoor workers, and low-income communities face higher exposure and lower capacity to cope. People with chronic illnesses, Indigenous communities, and those in informal settlements also have limited access to care and recovery resources.

How do air pollution and fossil fuel use interact with health outcomes?

Burning fossil fuels emits fine particles (PM2.5) and gases that inflame airways and raise heart disease risk. Wildfire smoke adds episodic spikes in dangerous particles. Together, these sources drive respiratory illness, stroke, and premature death while also producing greenhouse gases that worsen warming.

Can extreme heat increase death rates? Who is most affected?

Yes. Heat waves drive spikes in heatstroke, dehydration, and cardiovascular events. Older adults and people with heart or lung conditions face the highest mortality risk. Outdoor laborers and those without cooling or reliable electricity are also highly vulnerable.

How do floods and storms harm health systems?

Floods and storms cause immediate injuries and fatalities, damage hospitals and clinics, interrupt power and supply chains, and make it harder for patients to reach care. Disrupted water and sanitation raise infectious disease risks, while long rebuild times strain services.

What is the link between drought, water stress, and nutrition?

Prolonged drought reduces crop yields and livestock productivity, shrinking food availability and raising prices. Reduced water for hygiene and irrigation increases diarrheal disease and limits safe food preparation, driving higher malnutrition, especially among children.

Are vector-borne diseases changing with shifting weather patterns?

Yes. Warmer temperatures and altered rainfall can expand the season and range for mosquitoes and ticks, increasing transmission windows for diseases like dengue, malaria, and Lyme disease. This creates new risks in regions previously less affected.

What mental health effects arise from climate-related events?

Disasters and prolonged environmental stress cause trauma, anxiety, depression, and grief. Loss of homes, livelihoods, and social networks can produce long-term psychosocial harm, especially where mental health services are scarce.

How unequal are the health burdens between countries?

Low- and middle-income nations bear disproportionate harm due to greater exposure, limited health infrastructure, and fewer financial resources. Many developing countries face higher disease burdens, food insecurity, and challenges adapting health systems.

What role can health systems play in cutting emissions?

Health systems can reduce their carbon footprint through energy efficiency, switching to renewable power, adopting low-carbon procurement and supply chains, and improving waste management. These steps lower operational emissions while often saving money.

What are scopes 1, 2, and 3 emissions in healthcare?

Scope 1 covers direct emissions from facilities and vehicles. Scope 2 covers purchased electricity and heat. Scope 3 includes upstream and downstream supply-chain emissions, like pharmaceuticals, medical devices, and patient and staff travel—often the largest share.

Are there proven programs that guide health-sector decarbonization?

Yes. National and international initiatives—such as the NHS net zero program and global health coalitions—offer roadmaps for emissions measurement, efficiency upgrades, renewable procurement, and resilient facility design. Lessons from these efforts can inform local strategies.

How can health be integrated into national climate plans by 2030?

Governments can embed health priorities in Nationally Determined Contributions and adaptation plans, fund climate-informed surveillance and early warning systems, strengthen primary care, and finance community-level resilience measures to protect vulnerable populations.

What actions can individuals take to protect themselves and their communities?

Stay informed about heat and air quality alerts, prepare emergency kits, support local early warning systems, get vaccinated where recommended, reduce exposure during smoke events, and advocate for stronger public-health planning and cleaner local energy.

How important is financing for protecting health in vulnerable regions?

Critical. Adequate funding supports early warning systems, resilient clinics, clean energy in facilities, and social protections that reduce exposure. International finance and targeted domestic investment help developing countries build capacity and save lives.