The World Health Organization (WHO) has reviewed its fact sheet on climate change and health.
In the last 130 years, the world has warmed by approximately 0.85 degree Celsius. Each of the last 3 decades has been successively warmer than any preceding decade since 1850.
Sea levels are rising, glaciers are melting and precipitation patterns are changing. Extreme weather events are becoming more intense and frequent.
Climate change affects social and environmental determinants of health – clean air, safe drinking water, sufficient food and secure shelter.
Effect of climate change on health
1. Extreme Heat:
Extreme high air temperatures contribute directly to deaths from cardiovascular and respiratory disease, particularly among elderly people. In the heat wave of summer 2003 in Europe for example, more than 70 000 excess deaths were recorded.
High temperatures also raise the levels of ozone and other pollutants in the air that exacerbate cardiovascular and respiratory disease.
Pollen and other aeroallergen levels are also higher in extreme heat. These can trigger asthma, which affects around 300 million people. Ongoing temperature increases are expected to increase this burden.
2. Natural disasters and variable rainfall patterns:
Globally, the number of reported weather-related natural disasters has more than tripled since the 1960s. Every year, these disasters result in over 60 000 deaths, mainly in developing countries.
Increasingly variable rainfall patterns are likely to affect the supply of fresh water. A lack of safe water can compromise hygiene and increase the risk of diarrhoeal disease, which kills approximately 760 000 children aged under 5, every year. In extreme cases, water scarcity leads to drought and famine.
Floods contaminate freshwater supplies, heighten the risk of water-borne diseases, and create breeding grounds for disease-carrying insects such as mosquitoes. They also cause drownings and physical injuries, damage homes and disrupt the supply of medical and health services.
Rising temperatures and variable precipitation are likely to decrease the production of staple foods in many of the poorest regions. This will increase the prevalence of malnutrition and undernutrition, which currently cause 3.1 million deaths every year.
3. Patterns of infection:
Changes in climate are likely to lengthen the transmission seasons of important vector-borne diseases and to alter their geographic range.
Malaria is strongly influenced by climate. Transmitted by Anopheles mosquitoes, malaria kills almost 600 000 people every year – mainly African children under 5 years old.
The Aedes mosquito vector of dengue is also highly sensitive to climate conditions, and studies suggest that climate change is likely to continue to increase exposure to dengue.
Measuring the health effects:
Climate change is expected to cause approximately 250 000 additional deaths per year between 2030 and 2050:
- 38 000 due to heat exposure in elderly people,
- 48 000 due to diarrhoea,
- 60 000 due to malaria, and
- 95 000 due to childhood undernutrition.
Who is at risk?
Although climate change affects everyone, some are more vulnerable than others:
- People living in small island developing states and other coastal regions, megacities, and mountainous and polar regions are particularly vulnerable.
- Children – in particular, children living in poor countries – are among the most vulnerable to the resulting health risks and will be exposed longer to the health consequences.
- The health effects are also expected to be more severe for elderly people and people with infirmities or pre-existing medical conditions.
- Areas with weak health infrastructure – mostly in developing countries – will be the least able to cope without assistance to prepare and respond.
Link to the fact sheet:
Link to WHO document ‘Global Health Risks: Mortality and burden of disease attributable to selected major risks’ (2009):
Link to WHO’s climate change and human health page: