June 2023 was declared as the hottest June ever and the first week of July was identified as the hottest week recorded in human history. The World Meteorological Organisation (WMO) attributed this to continuing climate change compounded by the early advent of an El Nino weather pattern. As record temperatures were recorded, the WMO warned of “potentially devastating impacts on ecosystems and the environment” and said, “This is worrying news for the planet.” North India and north-eastern US experienced flooding from torrential rainfall, while southern parts of both countries and much of Europe sizzled in heat waves. As the pendulum of extreme weather events swings wildly in the ticking clock of climate change, it is not just ‘global warming’ that we see but ‘global harming’ too.
Climate change endangers human health and wellbeing through many adverse effects, which will be especially harsh on the poor and vulnerable sections of the population. Heat results in water and electrolyte loss from the body, dangerous to all but much more so to young children and the elderly. Heat exhaustion, heat stroke, circulatory failure, and death are effects of escalating severity. Brain strokes can result in paralysis or death. Heart attacks too are precipitated by heat stress. The kidneys can be damaged and can fail. Lung disease is exacerbated as hot air damages the lung tissues and the risk of pulmonary embolism increases as blood clots formed in leg veins dislodge and reach the lungs. Congenital cataracts and severe vision damage in older adults are reported adverse ocular effects of rising temperatures.
As the weather gets warmer, insect vectors of viral, bacterial, and parasitic transmission proliferate. Mosquitos, which spread malaria, dengue and chikungunya, can breed at higher altitudes and for longer periods of the year, increasing their territorial span and stretching the calendar of these infections. As floods contaminate drinking water sources and droughts limit the availability of potable water, waterborne infections will increase. Cholera is a dreaded threat during floods. Typhoid infections increase by 5-10% for every 1°C rise in temperature. Deforestation, a cause of climate change, also opens the road for zoonotic pathogen transmission.
Global warming triggers and prolongs wildfires in forests. Inhalation of chemicals and their smoke results in inflammation, increased oxidative stress, blood clotting, abnormalities of blood lipid and sugar profiles, gene mutations, raised blood pressure, heart attacks, and strokes. Particulate matter (PM 2.5), ozone, carbon monoxide, nitrogen dioxide, and polycyclic aromatic compounds increase the risk of cardiovascular and metabolic disorders, while benzene and formaldehyde exposure leads to cancers.
Fossil fuel combustion is a common cause of climate change and air pollution. As the carbon dioxide dome created by such combustion descends closer to the earth’s surface, pollutants are trapped closer to the ground and their density increases in the air we breathe. Wildfires contribute to air pollution, which injures heart, blood vessels, lungs, and brain. While people at all ages are affected, air pollution’s effects on pregnancy outcomes and child development heighten concerns about the intergenerational impact of climate change.
Mental health is also affected by climate change. As global warming and extreme weather events increase, mental health is affected by anxiety, anger, fear, or depression. Displacement and forced migration (of climate refugees) also undermine mental health. Worry, even at present, about what the future might hold as a consequence of climate change has been identified as a specific mental health disorder (solastalgia).
Deviations from temperature and precipitation patterns have been correlated with a significant rise in conflict. A study published in 2014 reported that a 1°C rise in temperature increased the frequency of interpersonal conflict by 2.4%, while intergroup conflict increased by 11.3%. As water insecurity, food insecurity, and displacement increase, conflicts will escalate.
Climate change poses a serious threat to nutrition, health, and wellbeing via its effects on agriculture and food systems. Global warming affects the quantity of crop yields and their nutrient quality. Both staples and non-staples are affected. Even now, in most parts of south Asia and sub-Saharan Africa, rice and wheat are grown at the highest limits of their temperature tolerance. For every 1°C further rise in the temperature, there would be a 10% fall in their production in these regions. Nutrient-rich crops will be more susceptible to droughts, pests, diseases, and temperature fluctuations. Fruits and vegetables will ripen and rot early. The shortage of water and fodder for cattle will affect dairy production.
The nutrient quality of crops will decrease due to higher carbon dioxide levels in the atmosphere and soil degradation. The protein, zinc, and iron content of staples will be reduced. A study from Columbia University’s Data Sciences Center, published in 2018, projected that unchecked climate change can result in the India of 2050 having 49.6 million new zinc deficient people, 38.2 million new protein deficient people, while 106.1 million children and 396 million women would become iron deficient. A switch to climate resilient crops, like millets and sorghum, would reduce that danger. At higher temperatures, arsenic levels in rice increase.
We need climate-smart agriculture too. Why should a health-harming, water- and pesticide-intensive crop like tobacco be grown extensively on arable land, instead of nutrient-rich crops? Should millions of litres of drinking water be used to produce sugar-sweetened commercial beverages? Ultra-processed packaged foods not only divert fresh produce from healthy diets but also add to global warming by having long supply chains, which burn up fossil fuels.
As sea levels rise with global warming, coastal agriculture will be damaged. The increasing salinity of water has affected agriculture and fishing in Sunderbans. Across India’s coastline of over 7,000 km, fish yield is being affected by climate change. It has been reported that the marine fish catch has fallen since 1996 at an annual rate of 1.22 metric tonnes. Ocean warming will impact fish diversity, distribution, abundance, and phenology.
Extreme weather events like torrential rain and floods disrupt health services, while epidemic outbreaks divert attention from other health needs. We must combine measures for mitigation and adaptation if we have to limit the harm to health from climate change. Hastened energy transition from fossil fuels to renewables must be coupled with heat action plans and investment in climate-resilient food and health systems.
The author is Cardiologist, epidemiologist, and distinguished professor of public health, PHFI