While climate change predominantly affects the environment, it directly and indirectly impacts health. Climate change is expected to exacerbate health problems that already pose a major burden to vulnerable populations. A recent international study in the Lancet says that many more people will be exposed to extreme weather events over the next century than previously thought—“a potentially catastrophic risk to human health” that could undo 50 years of global health gains.

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 – clean air, safe drinking water, sufficient food and secure shelter.

Negative imacts of climate change on health:

• 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.
• 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 over 500 000 children aged under 5 years, every year. In extreme cases, water scarcity leads to drought and famine. By the late 21st century, climate change is likely to increase the frequency and intensity of drought at regional and global scale.
• 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.
• Changes in climate are likely to lengthen the transmission seasons of important vector-borne diseases and to alter their geographic range.
• More heat can mean longer allergy seasons and more respiratory disease. More rain increases mold, fungi, and indoor air pollutants.
• 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. The Aedesmosquito 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.

Indian examples:

• The floods in Mumbai (2005) and Kerala (2018) were followed by outbreaks of leptospirosis or rat fever.
• Air pollution associated with climate change is a major risk factor for an increase in asthma and respiratory problems, especially among children in urban areas.
• The melting of glaciers result in the formation of glacial lakes, which may burst to cause flash floods that could be detrimental to people living in the Himalayan and sub-Himalayan region.

Way forward:
Without adequate investment in health sector resilience, recent development gains are at risk. Many countries and development institutions have recognized the importance of building climate resilience into the health sector. 121 of 184 (66%) Nationally Determined Contributions (NDCs) include references to climate change’s impacts on health, driven by strong support for action in many developing countries (90% of African states, 69% of Asian states, 82% of Latin American states). Readiness to tackle health issues due to climate change holds the key. The health sector must take a lead in these efforts specifically by systematically strengthening its response capacity by establishing an integrated environmental and health surveillance and early warning system. With the ability to anticipate the impact of climate change, health system must be prepared for an effective and rapid response to health emergencies, including disasters.