Health and climate change

Greatest challenge of this century

Climate changes threatens access to clean air, safe drinking water, nutritious food supply and safe shelter. It is already causing rising sea levels, more frequent and extreme weather events, heatwaves and droughts, forest fires and increased spread of mosquito-borne diseases like malaria.

A highly conservative estimate of 250 000 additional deaths each year due to climate change has been projected between 2030 and 2050: of these, 38 000 from heat exposure among the elderly; 48 000 from diarrhoea; 60 000 from malaria; and 95 000 from childhood undernutrition.

Taking action

Meeting the goals of the Paris Agreement could save about a million lives a year worldwide by 2050 through reductions in air pollution alone. The health benefits far outweigh the costs of meeting climate change goals, and the benefit-to-cost ratio is even higher in countries such as China and India. The same human activities that are destabilizing the Earth’s climate also contribute directly to poor health. The main driver of climate change is fossil fuel combustion – also a major contributor to air pollution which causes 7 million premature deaths worldwide every year.

The human cost

From the tropics to the arctic, climate and weather have powerful direct and indirect impacts on human life. The most disadvantaged, vulnerable and poor populations are expected to be disproportionately affected by climate change, with rising food and water insecurity, higher food prices, loss of income and livelihood opportunities, negative health effects, and population displacement (including forced migration).

Effects on nutrition

Climate variability and extremes are among the leading causes of severe food crises, and affect the nutrient quality of crops, dietary diversity of food produced and consumed, water and sanitation, patterns of health risks and disease, as well as changes in maternal care, child care and breastfeeding.
On the other end of the scale, the meat and dairy industries contribute to approximately 15% of greenhouse gas emissions and diets that are high in meat and dairy increase risks of cancer and cardiovascular disease. 

Rising sea levels

Rising sea levels are already causing population displacement, particularly in island states. More than half of the world's population now lives within 60 km of coastlines. Floods can directly cause injury and death and increase risks of diseases. Population displacement can increase tensions and potentially the risks of conflict. In 2017 WHO launched a Special Initiative on Climate Change and Health in Small Island Developing States. While these countries contribute very little to causes of climate change, they are among the most vulnerable to climate change impacts.

Water

More variable rainfall patterns are likely to compromise the supply of safe drinking water. Globally, water scarcity already affects 4 out of 10 people. A lack of safe drinking water increases the risk of diarrhoea (which kills approximately 2.2 million people every year), trachoma (an eye infection that can lead to blindness) and other illnesses. Water scarcity also means people are forced to transport water long distances and store supplies in their homes. This can increase the risk of household water contamination.

Air pollution

The most direct link between the drivers of climate change, and of poor health, is air pollution. Burning fossil fuels – for power, transportation and industry – is the main source of the carbon emissions driving climate change, and also a major contributor to air pollution, that kills 7 million people every year. Black carbon, produced by inefficient combustion in sources such as cookstoves and diesel engines, is the second greatest contributor to global warming. Over 90% of the urban population of the world breathes air that exceeds WHO’s guideline levels for outdoor air pollution.

Extreme heat

Heat stress can lead to increased death rates from heart and respiratory diseases, particularly in elderly or vulnerable populations.  With 1.5°C warming, 350 million more people could be exposed to deadly heat stress by 2050. Pollen and other aeroallergen levels are also higher in extreme heat. These can trigger asthma, which affects around 300 million people. Warmer climatic conditions also increase the risk of deadly water-borne and mosquito-borne diseases.

Cities can make a difference

Many of the necessary actions to reduce carbon emissions, improve health and increase resilience occur at the subnational level, particularly in cities.  Local authorities are often wholly or partly responsible for services including energy provision, transport, and water and sanitation and health.  Cities in particular are important drivers for climate and health action.

Positive co-benefits

Steps to reduce greenhouse gas emissions can have more immediate positive health effects. For example, promoting the safe use of public transportation and active movement - such as biking or walking as alternatives to using private vehicles - reduces carbon dioxide emissions and air pollution. It can also reduce traffic injuries and increase levels of physical activity which helps prevent diseases like diabetes, heart disease and cancer.