Is Bengaluru losing its cool?

Experts cite multiple reasons for the rise in temperature of the tech capital, including the impact of El Niño, the heat-island effect resulting from diminishing green cover and encroachments on water bodies, concretisation, and the prevalence of glass facade buildings.

After reaching 36.6°C on March 30, the hottest it's been in that month in the past five years, Bengalureans are feeling the heat. On April 2, it reached 37.2°C, and met department officials said the mercury may continue to rise.

The worry now in the IT capital of India, already facing a water crisis in some areas, is whether the temperature will surpass the highest of 39.2°C recorded in April 2016 or touch 40°C, possibly for the first time in Bengaluru's history.

Experts cite several reasons for the rise in the temperature of the tech capital, including the impact of El Niño, the heat-island effect, concretisation, and glass facade buildings.

Harsh summer

Bengaluru, situated at more than 3,000 feet above sea level, boasts its pleasant weather as its major USP, which attracts a young, talented workforce from across the globe. However, this time, the summer has been harsh - there's been no rain for more than 130 days, borewells are running dry, and water supply is reduced and restricted.

Also, read: First floods, now dry days: Decoding tech hub Bengaluru’s water woes

The sale of air-conditioners, once considered a luxury, has increased. Cases of food and water-borne diseases and heat-related illnesses are on the rise, and citizens are sweating it out. With schools breaking for summer holidays, those with the option of working from home have left the city.

"Bengaluru has changed a lot, and this summer is one of the worst. I had to rent out an AC from a startup, which I never thought of doing before. It's been a long time since I've seen rain," said Shahana Sheriff, a techie in East Bengaluru.

El Niño Impact

The met department said the main cause of rising temperatures this summer is the El Niño, a phenomenon characterised by the periodic warming of sea surface temperatures across the east-central equatorial Pacific that disrupts the usual supply of moisture and causes severe drought in some places and rains and floods in others.

"In February, the average temperature in Bengaluru was 1.3°C higher than normal and 1.6°C higher than last year," A Prasad, a scientist at the India Meteorological Department in Bengaluru, told Moneycontrol. "We did not experience any rain in February either. This can be attributed to El Niño, leading to severe heat, especially in peninsular India. In Bengaluru, light rainfall is expected on April 9 or 10."

What went wrong?

When Kempe Gowda, the founder of Bengaluru, embarked on the task of building his envisioned capital in the 1530s, his mother advised him: "Keregalam kattu, marangalam nedu," which translates to "Build lakes, plant trees."

Gowda heeded his mother's advice, created lakes, and increased greenery by planting trees throughout the region.

Bengaluru was a sleepy town, known as the Pensioner's Paradise, where people didn't even use fans. Everything changed after the IT boom in the 1990s and the city transformed into India's Silicon Valley, becoming the tech and startup capital. The lakes and gardens turned into a concrete jungle due to rapid urbanisation, giving way to tech parks, apartment complexes, and infrastructure projects.

"Bengaluru's rising temperature can be primarily attributed to unplanned and irresponsible urbanisation," TV Ramachandra, head of the Centre for Ecological Studies at the Indian Institute of Science, told Moneycontrol. "The loss of our natural heat sinks such as vegetation and water bodies has contributed to this."

In the 1800s, Bengaluru had 1,452 water bodies covering 740 square km. Today, there are only 193, he said. "Over the past 80 years, there has been a drastic decline in green cover, from 68 percent to a mere 8 percent, while the paved surfaces have increased to 86 percent. This extensive paving reflects radiation and adds to the temperature, unlike water bodies and vegetation, which act as heat sinks," said Ramachandra.

Also, read: How Bengaluru transformed from a pensioner’s paradise to a ‘swalpa adjust maadi’ city

Aditya Gowda, a private weather blogger who runs the Karnataka Weather handle on social media site X, said, "Whenever we experience El Niño, temperatures soar. For example, in 2016, we had severe temperatures, with Bengaluru recording its highest-ever temperature of 39.2°C in April. This situation repeats itself due to rapid urbanisation, resulting in the urban heat-island effect."

Heat-island effect

Another reason, according to experts, is the heat-island effect, where urban areas are warmer than their surrounding rural areas, mainly due to massive tree felling over the years.

Harini Nagendra, director of the Centre for Climate Change and Sustainability at Azim Premji University, told Moneycontrol: "When we pour so much concrete into the city, it increases the urban heat-island effect because concrete and cement absorb a lot of heat, whereas trees would have substantially cooled the city. In our research, we found that having trees on roadsides can lower the ambient air temperature by about five to seven degrees and the road surface temperature by 25 to 30 degrees."

There is some impact of global warming, but more significantly, the urban heat-island effect is due to the loss of lakes, wetlands, and trees, all of which used to cool the city, she said.

"To mitigate this effect, we need to restore the lakes and wetlands, plant more trees, and ensure there is much more vegetation overall. We need much less concrete and much more vegetation," she added.

Dattatreya Devare, a trustee of the Bangalore Environment Trust who has filed multiple public interest litigation petitions (PILs) against the felling of trees for the metro and other projects, said: "For various infrastructure projects like the metro, suburban rail, and road widening, we have lost a lot of trees. Despite some compensatory plantation happening after our PILs, it's not adequate, especially along the roads...  They should prioritise planting along the roads to mitigate the heat-island effect."

Revive lakes, promote rainwater harvesting

IISc professor Ramachandra said groundwater scarcity due to over-exploitation has led to the drying up of lakes, increasing the heat problem. He said these lakes can be revived.

"For example, Sarakki Lake, which was rejuvenated three years ago, saw groundwater levels increase by 320 feet within a year. Today, while most parts of Bengaluru face higher temperatures and water crises, Sarakki Lake has good water quality and a stable groundwater table. As a result of the surrounding greenery and clean water, the temperature at Sarakki Lake is at least three to four degrees lower than in other parts of Bengaluru."

He also emphasised that areas with more vegetation and water bodies tend to have a more moderate microclimate.

"The mini forest in the IISc campus significantly reduces the temperature compared to the rest of the city. The groundwater table is 10 to 15 feet, and the temperature is at least four degrees lower than that of the city within the campus itself," he said.

Sandeep Anirudhan, a sustainability activist, said: "Bengaluru should implement an emergency green plan to restore its green cover. There's an urgent need to declare a climate emergency and enact emergency legislation to increase the greenery. This crisis is a result of misgovernance. Currently, there's a lack of planning. We need to appoint proficient ecologists and urban planners with a strong environmental ethos to devise a new master plan."

Also, read: Why India’s tech hub just cannot manage rain

Gowda highlighted that despite receiving 100 cm of rainfall last year, only 8 percent was harvested in Bengaluru due to inadequate rainwater harvesting measures. Bengaluru typically gets 107.7 cm of rainfall annually.

"This inefficiency is unsustainable. With advancing technology, we've regressed in our environmental management. Rainwater harvesting must be made compulsory to mitigate water crises," he said.

Glass facades

Ramachandra said glass facade buildings in the city absorb more radiation, leading to higher electricity consumption for cooling purposes.

"In a normal building, electricity consumption ranges from 750 to 1,200 units per person per year. However, in glass facade buildings, this consumption increases significantly to between 14,000 and 70,000 units per person per year," he said.

Higher electricity consumption leads to increased emissions and greenhouse gases, which worsen global warming and contribute to changes in climate, he said. Elangovan K, a member of the citizen group Whitefield Rising, agreed.

"The architectural trends such as excessive use of glass facades and reliance on air-conditioning increase heat issues. We need to rethink building designs to prioritise natural cooling methods suitable for our tropical climate rather than simply copy European designs. Without addressing these issues, we cannot effectively combat rising temperatures and environmental degradation," he said.

He expressed concern over compensatory reforestation practices, saying when trees are cut down for projects like road widening, it's essential that the compensatory efforts occur close to the affected area.

Anirudhan asked: "When Bengaluru was known as the Garden City, why did we prioritise constructing glass and steel buildings over structures that could coexist harmoniously with greenery?"

Decongest the city

Ramachandra said decentralising development and shifting major installations away from the city centre could alleviate the strain on Bengaluru's resources and prevent further environmental degradation.

"It's crucial for the community to recognise the severity of the situation and take proactive measures before the consequences become dire," he said.

Private weather blogger Gowda said Bengaluru cannot accommodate a population of more than 10 million. The current population is estimated at 16 million.

"With the current population density, the existing green cover is insufficient. Without trees, plants, or greenery, concrete generates more heat, and more than a crore (10 million) vehicles are running on roads. Transitioning to public transportation and revitalising lakes while conserving water are essential. Moreover, many IT parks have encroached on the city's lakes," he said.

The heat that Bengalureans now face is in stark contrast to the heavy rainfall some three years ago that led to waterlogging in some areas. Experts blamed the flooding on poor urban planning that allowed buildings to come up and obstruct the city's natural waterways.

While the city may eventually get some relief from the heat, the weather office said most parts of the country are in for above-normal maximum temperatures during April-June.

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