How does climate change affect human health?

Climate change brings with it an increase in malnutrition, mental health conditions, infectious disease spread and even death

Climate change is often thought of in terms of its effects on our physical environment: melting icecaps, rising sea levels, heat-waves and storms. But increasing evidence shows that the human impact – and in particular the impact on human health – will be a major challenge for scientists, politicians and ordinary people in years to come.

The precise extent of the impact is difficult to quantify exactly because there are so many different factors at play. But one thing is certain: climate change is having an effect, and as the planet warms up, that effect is only going to increase.

Illustration showing how rising greenhouse gas levels are triggering climate and environmental changes

Rising greenhouse gas levels are triggering climate and environmental changes that will affect human health in many ways.

1. Rising greenhouse gas levels

Which lead to:

2. Temperature rise

Which leads to:

3. Higher temperatures

4. Crop failure

5. Altered weather patterns

6. Injury

7. Homelessness

8. Ocean acidification

9. Marine ecosystem shift

10. Sea level rise 

These changes (from 3–10) in turn lead to:

11. Mass migration

12. Economic disruption

13. Malnutrition

14. Social unrest

15. Aquaculture failure

16. Infectious disease spread

17. Displacement




Illustration © Glen McBeth

Direct and indirect consequences

The first major health impact of climate change is the rise in rates of mortality and diseases caused by extreme weather events. These include floods, droughts, tsunamis, heat-waves and other disasters which kill thousands of people in both the developed and developing worlds. Over 280,000 people were killed by the Asian tsunami of 2004, for example, while the 2003 European heat-wave killed 15,000 people in France alone.

Disasters like these make the headlines, but the indirect health consequences of climate change are just as important. Higher temperatures pose major health risks to older people and raise the likelihood that those who work outside – such as farmers and builders – will suffer from heat exhaustion and heat stroke. Many killer diseases, including malaria and cholera, increase as temperature and rainfall increase. The mosquitos that carry the malaria virus, for example, thrive in hot and humid conditions – weather which climate change is likely to make more common.

Malnutrition and mental health

A third impact on human health is yet more indirect, and comes as a result of climate change’s effect on human society and economic development. Experts now think that climate change is raising rates of malnutrition and mental health, for example. The connection may not be obvious, so let’s take each issue in turn.

In the developing world, malnutrition is rising because crops are failing, and that’s happening because of extreme weather. Cycles of drought and flood in West Africa are making it harder and harder for subsistence farmers to grow enough food to feed their families. And when the rain does come, it washes the topsoil away, degrading the land, so it becomes even more difficult to cultivate crops in the future. As a result, people go hungry and children in particular suffer from malnourishment.

The impact of climate change on mental health is a relatively new field of enquiry, but it should not be underestimated. People who have survived droughts, floods, tropical storms and similar extreme weather events often lose their homes and their families. As a result, they can experience post-traumatic stress disorder, severe depression and other mental health problems. In developing countries, where the impacts of climate change are at their most severe, there is less access to mental health services, so symptoms go untreated and unchecked.


There are possible health benefits of climate change. Older people living in more temperate countries may be less at risk of dying from the cold during harsh winters, and farmers may find agricultural yields improve as a result of a longer summer.

However, the benefits are likely to accrue for small numbers of people in more affluent countries. The losers from climate change are expected to be the poor and vulnerable in the developing world.


Further reading

About this resource

This resource was first published in ‘Health and Climate Change’ in January 2009 and reviewed and updated in September 2014.

Ecology and environment, Health, infection and disease
Health and Climate Change
Education levels:
14–16, 16–19, Continuing professional development