On this page
- The short answer: what causes climate change
- The main causes of climate change
- Burning fossil fuels
- Industry and cement
- Agriculture and land use — including deforestation
- Transport and buildings
- The health sector’s own emissions
- How each cause reaches our health
- Who is affected first and worst
- What would slow it down
- Frequently asked questions
Key points
- Climate change at global level is driven mainly by increased greenhouse gases in the atmosphere, largely from human activities — especially burning fossil fuels — together with land-use change, and alongside natural factors that have always affected climate.
- Greenhouse gases trap heat.
- WHO reports that 3.6 billion people live in areas highly susceptible to climate change, and that low-income countries and small island developing states endure the harshest impacts despite contributing minimally to emissions.
Direct answer: Climate change at global level is driven mainly by increased greenhouse gases in the atmosphere, largely from human activities — especially burning fossil fuels — together with land-use change, and alongside natural factors that have always affected climate.
The short answer: what causes climate change
Greenhouse gases trap heat. Human activities have raised their concentration in the atmosphere, strengthening the greenhouse effect and warming the planet. Natural factors still matter, but they do not explain the recent pattern alone.
The main causes of climate change
Burning fossil fuels
Energy, transport, industry and buildings that burn coal, oil or gas release carbon dioxide. This is the largest human-caused source in global assessments, because fossil fuels have powered most modern energy systems.
Industry and cement
Industrial processes release greenhouse gases directly, and cement production releases carbon dioxide as limestone is heated.
Agriculture and land use — including deforestation
Farming releases methane and nitrous oxide. Clearing forests removes trees that would otherwise store carbon, and the cleared land is often used for farming or development — so land-use change both releases stored carbon and reduces future storage.
Transport and buildings
Vehicles, shipping, aviation and the energy used to heat, cool and light buildings add carbon dioxide and other greenhouse gases.
The health sector’s own emissions
The health sector itself is a significant contributor to carbon dioxide emissions, according to the WHO compendium on climate change and health — a point health systems themselves are working to address.
How each cause reaches our health
| Cause | Pathway | Population-level health effect (WHO fact sheet) |
|---|---|---|
| Burning fossil fuels | Heat, air pollution | Heat stress; air quality worsens as temperatures rise |
| Land-use change, deforestation | Food and water systems | Food and water insecurity as rainfall and temperature patterns shift |
| Agriculture, waste | Water and food-borne routes | Changing patterns of water- and food-borne disease at population level |
| All causes together | Extreme weather, displacement | Floods, storms, droughts and displacement, with health effects on affected populations |
These are population-level pathways from the WHO climate and health fact sheet. Disease-outcome detail is outside this article’s scope.
Who is affected first and worst
The effects are uneven. WHO reports that 3.6 billion people live in areas highly susceptible to climate change, and that low-income countries and small island developing states endure the harshest impacts despite contributing minimally to emissions. Climate change is expected to cause about 250,000 additional deaths per year between 2030 and 2050 from undernutrition, malaria, diarrhoea and heat stress, with direct health damage costs of US$2–4 billion per year by 2030 (WHO fact sheet).
What would slow it down
WHO’s response, in plain words: cut emissions while improving health — cleaner energy, transport and food systems that also improve health; climate-resilient health systems that keep working through extreme weather; and holding warming to the 1.5°C goal. These are population-level actions, not personal advice.
Frequently asked questions
Is climate change already affecting health?
Yes — heatwaves, floods, and food and water stress are already increasing, according to WHO.
Do natural factors still matter?
Yes. Volcanic activity, changes in the Sun’s output and Earth’s orbit affect climate over long timescales. But models with only natural factors do not match the observed long-term warming; models that include human-caused greenhouse gases do.
Is this article about personal actions?
No. It explains global causes only, following the scientific consensus, with no personal advice.