Why some parts of Chennai felt hotter than others this summer


heat island effect
Increasing urban temperatures are a factor of the heat island effect that can be felt in cities. Pic: Faiz Binjai (CC BY 2.0)

The summer of 2019 was not kind to the residents of Chennai. Heatwaves through the last three months and acute water scarcity has made the lives of residents miserable and desperate for some relief through rains. But why is the summer becoming increasingly brutal with each passing year?

Rising annual temperatures have been a concern across the globe, and various studies indicate that Chennai is no exception to this trend. The nature of urban spaces also contributes significantly to this increase in temperature. Construction activity, pollution and loss of green cover all play a role in the hotness of summer, thus affecting the city and residents in various ways. 

Urban heat islands

The phenomenon of Urban Heat Islands (UHI) is now often heard of in Indian cities. An urban heat island is identified as an urban area that faces significantly higher temperatures than the surrounding rural or semi-rural areas, caused primarily by human activity. The most common among such activities are the ones alluded to above: increased construction, vehicular and greenhouse emissions, and felling of trees to facilitate development work. So which of these has been most prominent in Chennai?

Chennai has experienced the Urban Heat Island effect due to increased concretization. A study conducted by researchers at Anna University’s Center for Climate Change and Adaptation identified pockets of the city that had high temperatures as a result. The study covered a period between 1991 – 2008 and found that the intensity of heat islands had risen between 1-2 degrees over the time period. 

The research also found that temperatures during the day in the construction-heavy centres of the city were 3-4 degrees higher than surrounding outskirts which had greater tree cover and fewer buildings. Notably, the commercial hub of T Nagar and the industrial area of Ennore which is home to a thermal power plant registered higher temperatures. 

What amplifies the heat island effect in construction zones is the increase in paving and use of materials such as concrete, that radiate heat into the atmosphere. The paving should ideally be offset by vegetation and tree cover to mitigate the effects. But city-based organisation Care Earth Trust found that there has in fact been a decline in tree cover in the city, particularly in the aftermath of Cyclone Vardah of 2016. Only 15% of the city has tree cover, with concentration in a few areas such as Adyar and Anna Nagar. The minimum tree cover requirement for a city the size of Chennai is 33% of its area.

Educating the public

The Environmentalist Foundation of India (EFI), spearheaded by Arun Krishnamurthy, which works on conservation of environment in the city, has recently started spreading awareness about the rise in temperatures and the various ways in which it affects residents. The aim is to explain ‘the heat island effect’ as one of the reasons behind searing temperatures in summer and the measures to be undertaken to cope with the changing ‘new normal’. 

We started focusing on heat islands within the city especially close to water bodies that we work on. That led to identifying several heat pockets like Madhya Kailash, Avadi, parts of Mount Road within the city owing to a large number of air conditioners, vehicular exhaust, increased glass facades, larger area of concrete around buildings and fewer trees,” says Arun.

The rise in temperature also has a ripple effect on other ecosystems in the city. During their work, EFI has come to understand that the rise also affects water bodies. “The increased concretization of earthen surfaces, reduced water-land interaction has had an impact on greater ground water extraction, thereby adding more pressure on neighbourhood lakes and ponds.” 

Impact on the body

Spike in mercury in the city has an undeniable effect on the human body over time. While we apparently adapt to temperatures over 40 degrees and they seem to grow more bearable, the human body does undergo changes.

“Over time, the human body tries to adapt to changes. But there is only so much that the body can withstand. With high levels of humidity in Chennai, even temperatures over 35 degrees can have an impact. This is especially true for the vulnerable population who do not have access to proper shelter from the heat and those who undertake strenuous physical work at high temperatures,” says Dr Shri of Apollo Hospitals. 

Arun also states that increasing exposure to air conditioning alters the body’s response to these changes. “The body’s ability to adapt to natural temperatures or external conditions have become a major challenge, as most middle income and higher income group citizens are in the constant care of conditioned spaces. This leads to stimulated behaviour and body adaption; the less we are exposed to natural conditions, the more the chances of natural adaptation issues.”

With unchecked urbanisation, pollution on the rise and decline in green cover, the searing temperatures seen by Chennai is only set to be on the rise. Mindful planning to climate-proof the city must include strategies to green the city, reduce vehicular emissions and an action plan to protect the city’s most vulnerable. Overall, a concerted push towards sustainable living is imperative.

Steps to beat the heat

Staying adequately hydrated is the most important step in handling high temperatures as the body loses water. In addition,

  • Avoid going out directly during midday if possible
  • Use an umbrella and sunscreen to minimise the effects of heat
  • Regulate your diet: eliminate spicy foods and consume food that cools the body
  • Wear suitable attire such as cotton clothes
  • Increasing green cover around homes wherever possible to reduce the heat trapping effect of buildings
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About Aruna Natarajan 183 Articles
Aruna is an Associate Editor at Citizen Matters. She has a BA in Economics and a PG Diploma in Journalism. She has also worked in a think-tank on waste management policy and with a non-profit in sport for development. She writes on civic issues, governance, waste, commute and urban policy. She tweets at @aruna_n29.