How does climate change affect health?

Climate change affects health through multiple pathways: direct effects of extreme heat; increased frequency and intensity of floods, droughts and wildfires; expanding ranges of vector-borne diseases (dengue, malaria, Lyme disease); threats to food and water security causing undernutrition and diarrhoeal disease; air quality deterioration; mental health impacts (eco-anxiety, displacement, disaster trauma); and forced displacement. WHO calls it the single biggest health threat facing humanity.

How many deaths will climate change cause?

WHO estimates that between 2030 and 2050, climate change will cause approximately 250,000 additional deaths per year from malnutrition, malaria, diarrhoea and heat stress alone — a conservative estimate that excludes many pathways. By 2030, health damage costs from climate change are projected at $2-4 billion per year. The Lancet Countdown on Health and Climate Change tracks and updates these estimates annually.

What diseases spread with climate change?

Several diseases are becoming more prevalent or spreading to new areas with climate change: dengue (expanding into southern Europe, North America, higher altitudes); malaria (moving to higher altitudes in Africa and Asia); tick-borne diseases including Lyme disease and tick-borne encephalitis (expanding northward in Europe); West Nile virus; and Vibrio infections (expanding to northern seas as temperatures rise). Diarrhoeal diseases increase with flooding and temperature rise.

How does air pollution connect to climate change?

Air pollution and climate change share the same root cause: fossil fuel combustion. Burning coal, oil and gas releases both greenhouse gases (CO2, methane) and health-damaging pollutants (PM2.5, NOx, ozone). Air pollution kills approximately 7 million people per year — predominantly from cardiovascular and respiratory diseases. Transitioning to clean energy would simultaneously address climate change and air pollution, generating massive immediate health benefits — the "co-benefits" of climate action.

What is extreme heat and why is it dangerous?

Extreme heat kills directly through heatstroke — when the body's ability to regulate temperature fails — and indirectly by exacerbating cardiovascular and respiratory conditions. WHO projects heatwaves will become the leading climate-related cause of death. Older adults, outdoor workers, urban residents and people with chronic conditions face the greatest risks. Urban heat islands amplify the effect in cities. The 2023 summer saw record temperatures across Europe, the Middle East and North America, with thousands of excess deaths.

What is the Paris Agreement and what does it mean for health?

The Paris Agreement (2015) commits countries to limiting global warming to well below 2°C and pursuing efforts to limit it to 1.5°C above pre-industrial levels. The 1.5°C threshold is critical for health: at 2°C, the burden of climate-sensitive diseases escalates sharply — more dengue cases, more heat deaths, more coastal flooding, more food insecurity. WHO considers the Paris Agreement the most important public health treaty of our time, even though it was not designed as a health treaty.

What was the COP28 Climate and Health Declaration?

At COP28 in Dubai (December 2023), over 140 countries signed the Declaration on Climate and Health — the first time health had been so prominently placed in global climate negotiations. Countries committed to developing climate-resilient, low-carbon health systems; integrating health into national climate plans (NDCs); scaling up health financing for climate adaptation; and holding the fossil fuel industry accountable for health costs. WHO called it a historic breakthrough.

How does climate change affect mental health?

Climate change affects mental health through multiple pathways: eco-anxiety (distress about climate change itself, particularly in young people); trauma and PTSD from extreme weather events (floods, wildfires, heatwaves); grief from ecosystem loss and displacement; and chronic stress from economic and food insecurity driven by climate impacts. The mental health impacts of climate change are now recognised by WHO as a significant and growing public health concern requiring integration into climate adaptation plans.

What is One Health and why is it relevant to climate and health?

One Health recognises that human, animal and environmental health are interconnected. Climate change disrupts this nexus: warmer temperatures change animal and insect habitats, bringing wildlife, livestock and humans into new contact; melting permafrost may release ancient pathogens; ecosystem disruption increases zoonotic disease risk. The same climate-altered ecosystems that drive vector-borne disease also threaten the food systems and biodiversity that underpin human health. One Health is therefore essential for climate-resilient health systems.

What can health systems do about climate change?

Health systems are responsible for approximately 4.4% of global greenhouse gas emissions — equivalent to the aviation and shipping industries combined. Climate-resilient, low-carbon health systems require: transitioning to clean energy (solar-powered health centres); reducing pharmaceutical waste; reforming anaesthetic gas management; sustainable procurement; and building physical climate resilience (cooling systems, flood protection). WHO's Alliance for Transformative Action on Climate and Health (ATACH) supports countries in developing climate-smart health systems.

How does GMJ News cover climate and health?

GMJ News tracks the Lancet Countdown on Health and Climate Change annual report, IPCC assessment report health chapters, COP climate and health outcomes, heatwave health impacts, and the expansion of climate-sensitive diseases. Georgia faces specific climate-health risks — including heatwaves in the lowlands, vector expansion and impacts on agricultural and water systems — that are priorities for PHIG and the Georgian Medical Journal.

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Climate Change and Health

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

Summary Statistics Glossary GMJ news FAQ Documents Organizations Research

WHO calls climate change the single biggest health threat facing humanity: between 2030 and 2050 it is conservatively projected to cause about 250,000 additional deaths a year from undernutrition, malaria, diarrhoea and heat stress alone, with health damage costs of US$ 2–4 billion a year by 2030. The mechanisms are already visible — deadlier heatwaves, expanding ranges of dengue and malaria vectors, floods and droughts undermining food and water security, and air pollution from the same fossil fuels driving warming. The COP28 Declaration on Climate and Health, endorsed by over 140 countries, finally put health at the centre of climate negotiations; GMJ News covers the science and the accountability.

Primary sources: WHO fact sheet — Climate change and health · WHO health topic — Climate change

Key messages

Greatest health threat

WHO calls climate change the single biggest health threat facing humanity. Between 2030 and 2050 it is projected to cause approximately 250,000 additional deaths per year from malnutrition, malaria, diarrhoea and heat stress alone.

Air pollution

Air pollution — driven by the same fossil fuels causing climate change — kills approximately 7 million people per year. Eliminating fossil fuel combustion would address both crises simultaneously.

Disease range expansion

Rising temperatures are expanding the geographic range of vector-borne diseases: dengue now threatens parts of Europe, malaria is moving to higher altitudes, and tick-borne diseases are expanding northward.

Food and water security

Climate change threatens food and water security through droughts, floods and agricultural disruption — with cascading effects on undernutrition, diarrhoeal disease and conflict, all major health determinants.

Extreme heat

Heatwaves are becoming more frequent, intense and prolonged. Heat kills directly (heatstroke) and indirectly (exacerbating cardiovascular and respiratory disease). Outdoor workers and older adults face the highest risks.

COP28 Health Declaration

The COP28 Declaration on Climate and Health, endorsed by over 140 countries in Dubai in 2023, placed health at the centre of climate negotiations for the first time — a historic shift in global climate governance.

Key statistics

250K

additional deaths/yr by 2030-50

WHO

deaths/year from air pollution

WHO

$2-4B

health damage costs/year by 2030

WHO

140+

countries signed COP28 Health Declaration

COP28 2023

4B+

people at risk from dengue expansion

WHO

1.5 C

Paris Agreement limit (critical health threshold)

IPCC

Global average surface temperature anomaly (°C above pre-industrial baseline) 1950-2023 — NASA/NOAA

Source: NASA Goddard Institute for Space Studies (GISS) / NOAA Global Surface Temperature Analysis.

Glossary of key terms

Climate-sensitive disease
WHO/IPCCA disease whose transmission, distribution, seasonality or severity is significantly affected by climatic variables (temperature, rainfall, humidity). Examples: malaria, dengue, diarrhoeal diseases, vector-borne encephalitis, heat-related illness.

Paris Agreement
UNFCCCThe 2015 international climate treaty targeting limiting global warming to well below 2°C above pre-industrial levels, and pursuing efforts to limit it to 1.5°C. The 1.5°C threshold is considered a critical public health inflection point — above it, health risks escalate sharply.

Urban heat island
WHOThe phenomenon whereby urban areas are significantly warmer than surrounding rural areas due to heat-absorbing surfaces, reduced vegetation and waste heat from human activity. Amplifies health risks during heatwaves, particularly for outdoor workers and older adults.

One Health
WHO/FAO/UNEP/OIEAn integrated approach recognising that human, animal and environmental health are interconnected. Climate change — by altering ecosystems, species distributions and agricultural systems — makes One Health approaches essential for managing emerging and vector-borne disease risks.

Loss and damage
UNFCCC/COP27A UNFCCC framework established at COP27 (2022) to address unavoidable climate impacts in vulnerable countries that cannot be prevented by mitigation or adapted to. Includes health system damage, displacement and economic losses.

Co-benefits
WHO/IPCCThe additional health benefits of climate action beyond climate change mitigation itself. Actions that reduce fossil fuel combustion simultaneously reduce air pollution, improve cardiovascular and respiratory health, and encourage active transport — generating substantial immediate health gains.