The hidden health fallouts of a warming world

Climate change has is the single largest global health challenge in the 21st century. The Framework Convention on Climate Change (UNFCCC) defines climate change as "a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere beyond the natural variations." A multi-country study has suggested that climate change is responsible for four lakh additional deaths each year and will contribute to seven lakh annual deaths by 2030.

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As per the UN, the world has endured a "decade of deadly heat", with 2024 capping 10 years of unprecedented temperatures. It is almost certain that it will exceed the Paris Agreement threshold of 1.5 degrees above the preindustrial levels of temperature for the first time. The World Meteorological Organisation has warned that the new year is likely to be worse, with the greenhouse gas levels growing to record highs.

India also recorded its warmest year in 2024. It witnessed extreme weather on 255 of the 274 days of the year’s first nine months, according to the Centre for Science and Environment.

The detrimental climatic factors for human health include an increase in the frequency and intensity of heatwaves, precipitation, floods and droughts. The floods in Spain, hurricanes in the US, drought in the Amazon and floods across Africa are just a few examples. In West Asia, 1,300 Haj pilgrims died due to extreme heat in 2024.

High temperature is known to increase the 'ground level ozone' and 'climate altering pollutants' other than carbon dioxide. They exacerbate cardio-respiratory and allergic diseases and certain cancers. Between 2000-2004 and 2017-2021, heat-related deaths increased by 55 per cent in India. Due to heat exposure, it lost 167.2 billion potential labour hours in 2021, with income losses equivalent to 5.4 per cent of the GDP.

An increase in the transmission and spread of infectious diseases and changes in the distribution of water-, food- and vector-borne diseases have also been seen. A 2022 study published in the 'Nature Climate Change' found that nearly 60 per cent of the infectious diseases are aggravated by climate hazards.

A warmer climate causes water-borne diseases, including cholera, and diarrhoeal diseases like giardiasis, salmonellosis (including typhoid) and cryptosporidiosis. It is estimated that one-quarter of children’s deaths in South Asia are due to diarrhoeal diseases. As temperatures increase, bacterial survival time and proliferation increase. Further, contamination of water during floods makes things worse. A relationship has been observed between an increase in the sea-surface temperature and cholera epidemics.

Malaria, dengue, chikungunya and leptospirosis have become more common in India with a longer duration of infectivity in the last two decades. Chikungunya and dengue are influenced by climate change as both are transmitted by the same vector: Aedes aegypti.

In 2023, some six million cases of dengue were reported worldwide — more than ever before. Alarmingly, in 2024, this number exceeded 12 million. Mosquitoes are exothermic or cold-blooded. So, when the temperature rises, everything that their body does speeds up. They grow faster and replicate the dengue virus in their guts more effectively. Between 1951-1960 and 2012-2021, the number of months suitable for dengue transmission has risen by 1.7 per cent.

Changes in temperature, humidity and rainfall are altering the global malaria map. In Africa, on either side of the Equator, there has been an increase by several miles of areas that are suitable for breeding mosquitoes each year due to deforestation and changes in temperature and rainfall. It has populations with  low immunity to malaria.

The warming atmosphere has been melting glaciers and ice sheets. Experts fear that micro-organisms of yet unknown significance may get activated after staying dormant for thousands of years.

The increase in zoonotic diseases (diseases spread from animals to humans) is also threatening mankind. With changes in the forest cover due to human activity, there has been a migration of certain bird and mammal species which are hosts to an array of pathogenic organisms that can cause diseases in humans. They include tick-borne encephalitis, haemorrhagic fever brucellosis and leptospirosis.

Although low- and middle-income countries are responsible for only a small percentage of global greenhouse gas emissions, the adverse health effects fall disproportionately on them because of poor health infrastructure, lack of funds and overpopulation.

This is the reason that at the COP-29 (29th Conference of the Parties of the UNFCCC), held in November 2024, India and other developing countries objected to the $300-billion per year funding agreed upon to prevent climate change. It fell way short of the demand of $1.3 trillion to meet the Paris Agreement's goal of limiting the global temperature rise.

While the India has formulated the National Programme on Climate Change and Human Health and the National Action Plan on Climate Change, how can individuals help? One of the most impactful ways to do so is to eat less meat. Meat animals release methane and nitrous oxide, which have a much stronger effect on global warming than carbon dioxide. Air travel is responsible for one-sixth of all emissions globally. Using other modes of transport can, thus, be helpful. Clothes also account for sizeable emissions. Recycling clothes and having a smaller wardrobe is a good idea. Using heating devices not based on fossil fuels is easy. Reducing the use of plastics is another way to contribute to sustainable living.

It is important to increase awareness about climate change since everyone is affected by it and every small measure counts. We owe it to the coming generations to save the planet.