Although global warming may bring some localized benefits, such as fewer winter deaths in temperate climates and increased food production in certain areas, the overall health effects of a changing climate are likely to be overwhelmingly negative. Climate change affects social and environmental determinants of health like clean air, safe drinking water, sufficient food and secure shelter. Moreover, 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 (UNEP, 2004, March). Noticeably high temperatures also raise the levels of ozone and other pollutants in the air that exacerbate cardiovascular and respiratory disease.
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 (WHO, 2017, July). Relating to the rising sea levels and increasingly extreme weather events particularly will destroy homes, medical facilities and other essential services. More than half of the world’s population lives within 60 km of the sea (Creel, 2003, September). And people may be forced to move, which in turn heightens the risk of a range of health effects, from mental disorders to communicable diseases. 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 diarrheal disease, which kills thousands children aged less than 5 years, every year. In extreme cases, water scarcity leads to drought and famine.
Floods are also increasing in frequency and intensity, and the frequency and intensity of extreme precipitation is expected to continue to increase throughout the current century. 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.
In addition, climatic conditions strongly affect water-borne diseases and diseases transmitted through insects, snails or other cold blooded animals. Changes in climate are likely to lengthen the transmission seasons of important vector-borne diseases and to alter their geographic range. For example, climate change is projected to widen significantly the area of China where the snail-borne disease schistosomiasis occurs (WHO, 2009). Malaria is strongly influenced by climate. Transmitted by Anopheles mosquitoes, malaria kills over 400 000 people every year – mainly African children under 5 years old (WHO, 2017, April).
To sum up, climate change normally affect all populations, but 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 that are among the most vulnerable to the resulting health risks and will be exposed longer to the health consequences.