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The sun never seems to take a break in Chennai, Tamil Nadu. It scorches the city, located less than 1,500 kilometres from the equator, and its residents throughout the year, making merely earning a livelihood a trial by fire.
Delayed sea breezes and rising night temperatures makes matters worse, as they keep the city from cooling down after sundown. Humidity joins the deadly concoction as a silent killer.
No one — not those at sea, shore or interior — is spared.
“We leave our nets in the summer. If we leave our nets, they will get decomposed. If the sun is too bright, the net would break. And we won’t be able to catch fish,” said Karnan, a fisherman who spends most of the day at sea.
Devi, a fish vendor on the beach, complained of the merciless heat during work hours. “I couldn’t take the heat, my head was spinning. I was feeling dizzy and was having trouble breathing. I can’t handle this heat.”
“If I can’t drive in the hot sun, I have to drive in the evening and continue through the night. There’s an option to drive all night, but I’m not sure if I can keep doing it for 10 years,” shared Senthil, a local auto driver.
Down To Earth travelled to Chennai to understand how the city and its citizens are adapting to this dangerous combination of heat and humidity. In this six-part series, DTE takes a closer look at how Chennai’s population, especially the coastal communities are adjusting to these scorching and perspiring summers and what steps are being taken to help the city’s residents survive the heat index.
Located on India’s southeastern coast, Chennai is a bustling city with a population exceeding 12 million. It’s unsurprising that the city is categorised as ‘warm-humid’, given that temperatures frequently rise above 40 degrees Celsius and humidity cling to the skin tighter than passengers in a packed Metropolitan Transport Corporation (Chennai) bus during peak hours.
According to Mitashi Singh, programme manager at Delhi-based think tank Centre for Science and Environment, said, “Nearly all days in the summer months in Chennai were falling under ‘extreme caution’ or ‘danger’ levels of heat index.”
When the heat index climbs above 41°C, it enters a hazardous zone for humans. In the relentless summer of 2023, Chennai didn’t just slip into it, but stayed there for 31 brutal days.
“Heat is not the only parameter here, it is also the thermal discomfort,” said Sudha Ramen from the Tamil Nadu State Planning Commission. “Unlike other disasters like floods and cyclones, which Chennai has also been susceptible to, heat is considered to be a silent disaster. So, not much attention was given to it.”
It is known that vulnerable communities are getting exposed to high levels of heat, which could alter a lot of their biological functions, making them more susceptible to health ailments, she added.
“Heat stress impact is most for people working in open areas, like construction or fishing. These people are not working under thermal neutralities,” said Lakshmi Kumar TV, associate professor at Jawaharlal Nehru University. According to studies, by 2060, work performance will decline by almost 35 per cent, he added.
Coastal communities, who make ends meet in the periphery, are central to Chennai’s urban fabric and play an important role in its identity. Extreme heat and humidity affects every part of the fishing economy — from catching and storing to sale of the fish and well-being of workers.
“In summers, our nets decompose and get damaged when left in the sun for too long. We can’t catch fish using that and are forced to change the net. Each new net costs around Rs 20,000 to Rs 30,000,” said Karnan, a local fisherman.
The city's fisherfolk spend up to 10 days at sea and have no respite from the blazing sun and heat reflecting off the waves. As they scan the waters, the glare strains their eyes, causing vision impairment, headaches and exhaustion. Their hands are always on the nets, even as the heat pushes their bodies to the limit.
“Throughout the day, fisherfolk are exposed to sun and heatstroke directly through sea waves, which reflect sunlight,” Bharathi, founder of South India Fishermen Welfare Sangam in Chennai, told DTE. “There is no speedboat with facilities to rest or protect from heat.”
“We always feel dehydrated and want to drink water,” said Karnan. “We usually drink kanji (fermented carrot drink) to cool ourselves down, mixing it with curd. It cools the body down and helps get good sleep. It also helps with the way our eyes itch when we go out in the seas during the summer,” Karnan shared, adding, “The heat gets to our heads sometimes. But what can we do? It’s the job.”
While the sea brings in the day’s catch, it’s the women who carry it into the city by working long hours in open markets with little to no shade.
Surrounded by metal and concrete over their heads in the form sheets and under their feet in the form of tarred roads, they endure heat that clings to the skin and refuses to let go.
One of these women, Devi, a fish vendor explained the presence of heat in her daily routine and added how the breeze has changed over the years.
“The wind circulation was better and made a lot of difference. We have been selling fish for 40 years, the heat has been manageable and we had systems in place,” she recollected.
"We never got this sick as well. Now, we go home, do our chores and only return to set up the shop at around 4pm. But now it even the heat at this hour is becoming difficult to manage. How can the fish survive in these conditions?”
Chennai’s sea breeze has traditionally served as a natural cooling system, providing respite from the city's warmth. In the summer, the area lacks large-scale weather systems, with the sea breeze circulation being the sole influencing factor. Yet, recent observations suggest a change in its patterns.
“In recent scenarios, 10-15 storey buildings are raised on seashore areas which makes the case much worse by not letting the sea wind / breeze enter the interiors of the city,“ Bharathi observed. Thus, people a bit away from the coast or deep inland cannot experience the wind, he added. This leads to intense hear and heat strokes, the expert noted.
In summers, the westerlies block the sea breeze from blowing into the city, thus closing the tiny window of comfort during the afternoons, said Lakshmi Kumar TV.
The city is choked with vehicular exhaust, he added. The black carbon aerosols from the exhaust absorb solar radiation, become warm and warm the surrounding regions as well, the professor explained.
The evenings are also hot, the locals told DTE. Even at 6pm, Devi showed how the bottom of her feet were burning. The heat is so severe that they get ulcers in the stomach, leading to a host of illnesses. This is also the reason why typhoids and other diseases keep spreading during this time.
Exposure to intense heat also increases the chances of fish catch getting rotten. Fisherfolk like Karnan have to, thus, scheme out ways to keep catch fresh and ready for sale. Ice boxes are a common feature at the shore and at the beach markets, especially during these summer months.
Chennai has seen a 70.35 per cent expansion in urban areas, mainly towards the suburban periphery between 1991 and 2016.
“We find that the built area environment has subsequently increased because of the push factor, urbanisation and the industrial requirement. Consequently, the urban heat island effect has become a more significant concern for Chennai,” said Ramen.
In the city’s burning streets, another kind of heat trap awaits. Behind the wheel of a metal box, auto drivers navigate traffic, fumes and rising temperatures.
Auto-drivers DTE spoke to talked about their dilemma regarding the best time to drive. Senthil, who has been driving an auto for 10 years, said, “It is difficult to drive in the hot sun. There is no other way. I have to find a place to sit and relax. Then I can drive," adding that driving all night for a long period isn't feasible for him.
His routine and earnings have been disrupted due to the extreme heat.
CSE’s Mitashi Singh explained how water vapour in coastal cities add to the misery. She said, “In coastal cities like Chennai, where the humidity levels are already high, the air traps more water vapour. And when there is more water vapour in the air, it heats up faster. It's a greenhouse gas after all.”
The Centre for Science and Environment conducted a heat index analysis in 2023. This was for the summer months which included a total of 153 days. The heat index is the combination of temperature and the relative humidity which actually tells you the ‘feels like’ temperature, said Nimish Gupta, deputy programme manager, CSE.
“Chennai was one of the worst-hit among the nine cities analysed, where all 153 days were under some form of heat stress. And of these, around 60 per cent of the days were under the danger category, wherein the heat index was between 38°C and 52°C.”
In the evening, the sun sets on Chennai’s horizon but the heat still hovers over it.
The city's concrete jungle traps heat during the day and slowly releases it into the night air, raising temperatures long after the sun sets.
Hot nights are as dangerous as midday peak temperatures. People get little chance to recover from the daytime onslaught of heat if temperatures remain high overnight, exerting prolonged stress on the body.
A study published in the Lancet Planetary Health noted that the risk of death from excessively hot nights would increase nearly six-fold between 2016 and 2100.
In the last two decades, Tamil Nadu has experienced a significant rise in night-time temperatures, with a 59 per cent increase in regions where temperatures range between 24-26°C. Chennai is notably affected, showing the largest change in night-time land surface temperature. Between 2001 and 2023, the average night-time temperature in Chennai increased by 1.5°C, rising from 23°C to 24.5°C.
“The urban heat island effect assessment shows that Chennai's night-time temperature is higher, with an approximate increase of 1.5 degrees over the past decade or two,” informed Ramen.
Senthil's home is covered by galvanised iron sheets that absorb heat. He told us that he often goes to the beach to sleep rather than enjoy the privacy of his own house.
Urbanisation cannot be controlled, but building designs can be influenced through use of sustainable materials, implementation of cool roof systems and the adoption of energy-efficient measures to lower greenhouse gas emissions. To help vulnerable communities manage heat and take preventive steps, hospitals have been provided with advisories.
The Department of Health has established a specialised unit known as One Health Labs, which focuses on the intersection of health and climate change. This initiative not only addresses human health but also considers the well-being of other living organisms.
Additionally, the Green Climate Company has been formed, featuring a flagship program dedicated to the climate change mission in Tamil Nadu.
Regarding heat, a significant action taken by the government was to designate heat as a disaster specific to the state. This designation allowed the use of the state’s disaster reserve fund to implement heat-related measures effectively. Additionally, families of those who die due to heat will receive an ex gratia payment of around Rs 4 lakh.