Beyond the thermometer: Bengaluru’s race to modernise ignored climate — now its residents are paying the price

“It is scorching hot. If I get tired or feel unwell, I cannot rest anywhere, as there is no place for us to take a break,” said Nagalakshmi, a sanitation worker with the Bruhat Bengaluru Mahanagara Palike (BBMP). Her words echo the reality faced by hundreds like her, caught in the throes of a city transformed by heat.

Once lauded as India’s Garden City — famed for its tree-lined avenues, sprawling parks and placid lakes that kept its weather temperate — Bengaluru now finds itself in the grip of a crisis. Since 1975, the city’s mean air temperature has risen by 0.23 degrees per decade.

The city’s climate has changed dramatically over the past few decades. According to TV Ramachandra, coordinator of the Energy and Wetlands Research Group at the Indian Institute of Science, “What was 19°C in the 1990s became 21°C in 2000. Today, it’s about 36-37°C. That is the change.”

Rapid, unplanned urban sprawl, the disappearance of waterbodies and relentless paving of open spaces are among the primary drivers of this shift. Bengaluru’s green cover has plummeted from 68 per cent in 1973 to just 6 per cent today.

More than 79 per cent of its waterbodies have either vanished or been encroached upon. As Anup Naik, founder-director of the urban planning studio Urban Frame, puts it, “Everything is becoming a hard surface now. Bengaluru’s first bus stand was originally a lake bed.”

Those worst affected — workers like Nagalakshmi — played no part in causing this transformation but are left to suffer its full impact.

Down To Earth (DTE) travelled to Bengaluru to investigate how one of India’s fastest-growing tech hubs is coping with extreme heat. In this six-part series, we explore the effects of rising temperatures — driven by vanishing green cover and disappearing lakes — on the city’s most vulnerable residents.

Rising heat in Bengaluru

Bengaluru, home to over 14 million people and widely recognised as India’s Silicon Valley, lies in the tropical savanna zone, with distinct wet and dry seasons. Once praised for its blend of technology, culture and greenery, the city is now infamous for not just its traffic but also its heat intensity. The warming has been most severe in the last decade, nearing 0.5°C per decade — a symptom of vanishing blue-green infrastructure.

“The city has experienced unplanned, irresponsible urbanisation,” Ramachandra told DTE. “Glass-façade buildings are unsuitable for tropical cities like Bengaluru, Chennai and Hyderabad. Wherever high-rises cluster, temperatures are 2-3°C higher than surrounding areas.”

Delhi-based think tank Centre for Science and Environment (CSE) has conducted a decadal analysis in which the surface temperatures were mapped, said Nimish Gupta, deputy programme manager for CSE. “Areas consistently crossing 41°C were marked as ‘heat centres’ and those with six or more years of recurrence were termed ‘heat-stressed zones’,” he said. 

These heat zones define the daily hardships of workers like Nagalakshmi, who walks 6-7 km a day under a relentless sun, sweeping streets with little shade or respite. “There’s no place to rest,” she said. “Even if we want to take a break, we hesitate to drink too much water — there are no toilets nearby.”

The works have written to BBMP officials for help, said Appan, head of the sanitation workers’ union. “The parks, which could offer some relief, are open only from 6 am to 10 am. Earlier there were more trees. Now, there are hardly any.”

Other workers like Hooliyamma have found their own coping mechanisms. “I tie a scarf over my head because of the intense sunlight. There are no parks. We can’t do much work in this heat.”

Today, over 85 per cent of the city is covered in built-up surfaces. With fewer permeable areas, Bengaluru’s ability to retain water and moderate heat has drastically diminished.

“A porous landscape retains moisture and cools the microclimate,” said Ramachandra. “Our studies show areas with lakes and vegetation are at least 2°C cooler. Unfortunately, some urban forest patches have been enclosed by influential elites. We must reclaim and convert them into green public spaces. The High Court has issued orders to remove encroachments.”

Urban heat island effect

Another contributor to Bengaluru’s rising temperatures is the urban heat island (UHI) effect. Mitashi Singh, programme manager at CSE, explained: “In UHI, city centres become hotter than surrounding rural areas due to dense construction, roads, parked vehicles and minimal greenery. Solar radiation is trapped in hard surfaces and keeps circulating, instead of escaping back into the atmosphere.”

Naik agreed that urban design plays a central role. “City planning often ignores basic ideas like building orientation and heat gain. High-density developments result in greater energy use and more air conditioning only worsens local heat levels. It’s a vicious cycle,” he added.

Recognising the crisis, BBMP has initiated lake rejuvenation projects. Nithya, executive engineer in BBMP’s Lakes Division, said their efforts include removing encroachments, redirecting sewage, desilting lake beds, developing wetlands and planting native species.

“We have 202 lakes within BBMP limits. Of these, 183 are live and 19 are disused. Development caused many to fall into disuse. But now, lake and tree restoration efforts have increased,” she said.

Predicting heat with AI

At ARTPARK (AI & Robotics Technology Park) in IISc, scientists are working on models to anticipate extreme heat. Computational scientist Vybhav GR and his team are developing tools that offer heat forecasts at the taluk (sub-district) level, helping cities better prepare for workers like Nagalakshmi.

“AI can analyse data in ways humans can’t. But the challenge is the availability of reliable, consistent climate data,” said Ravi Shankar Nanjundiah, professor ay IISc and chairman, Centre for Atmospheric & Oceanic Sciences.

The system allows users to select a state, district and sub-district, with a 10-day lead time, said Vybhav. “For each taluk, it shows the daily heat risk. It also includes information on infrastructure — like cooling centres — that can aid mitigation,” he added.

Bhaskar Rajakumar, programme director for health initiatives at ARTPARK, noted that factoring in socio-economic vulnerabilities, health risks and exposure levels can make alerts more targeted and life-saving.

Yet, while researchers draft forecasts and policies from air-conditioned labs, workers like Nagalakshmi continue their duties in “heatzones.”

“We need a proper place to rest during our breaks — especially since we work outdoors, under direct heat,” she said.

After another long, sweltering day, Nagalakshmi returns home. She lies down on the bare floor — the only surface in her house that offers a trace of coolness. 

For now, that is her only moment of rest.