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With just a week to go for the originally scheduled reopening of schools in Tamil Nadu on June 1, the State has decided to heed the warnings on oppressive summer temperatures and postponed the date to June 7. Minister Anbil Mahesh Poyyamozhi had earlier said the schools would reopen as scheduled, while some demanded that the long spell of high temperatures should lead to a postponement.

At the heart of the issue is the severe heat felt across several districts of the State including Chennai, raising the question of exposure of the population, especially children and outdoor workers, to dangerous “wet bulb” temperatures.

According to the European Centre for Medium Range Weather Forecasts, wet bulb temperature is “the temperature recorded by a thermometer with its bulb covered by a wet cloth or wick. The greater the difference between the dry-bulb and wet-bulb temperature, the lower the humidity.”

Amidst the on-going heatwave, Minister Mahesh Poyyamozhi needs to seek scientific consensus on reopening schools on June 1

As humidity rises and so does ambient temperature, the difference between wet and dry bulb temperatures shrinks, sometimes touching dangerous levels. By scientific accounts, exposure to a wet bulb temperature of 31 degrees C can be harmful to the human body, affecting brain, heart and kidney function. At high levels of exposure to 35 degrees C wet bulb temperature, people are almost certain to die. That is because the body is unable to adjust to the heat through sweating, as the high humidity reduces or prevents evaporation.

It is a cause for worry that the Indian subcontinent, and the Indo-Gangetic Plain in particular, are on course to become hotter over time due to climate change – caused by release of high levels of carbon dioxide through human activity. While 2022 also caused severe heat stress in north India, temperatures in the current year are challenging, and threatening to become hazardous due to the impending onset of an El Nino. According to US climate scientist James Hansen and his colleagues, 2024 could well become the hottest year known to humanity, with disastrous consequences in several countries.

Also Read: Can Tamil Nadu coast survive deadly wet bulb temperature?

So what can we do?
Although Tamil Nadu has a better record at development than other States, and has a formal approach to climate action, it has been slow to act on emerging environmental threats.

The State has a Heatwave Action Plan (HAP) dating back to 2019, and the DMK government announced expensive projects like sponge parks and green commons for Chennai, but these are in slow-baking mode. For instance, Sholinganallur, a real-estate focused suburb on the IT Corridor, is scheduled to get two sponge parks and seven ponds. This is partly explained by the history of real estate developers occupying large marshes and reed beds that existed in the area. Pallikaranai, another massive marsh, has shrunk by 90% over time affecting the micro-climate and preventing flood water drainage.

Tamil Nadu’s 2019 HAP prescribes some fundamental protocols to be followed. It says, “The Greater Chennai Corporation, other Corporations in Tamil Nadu, the Municipalities, Town Panchayats, and Village Panchayats, may have to promote establishment of Bio Shields in their area and increase the green cover.” Educational institutions, including private ones, are also advised to do the same. A big tree planting campaign in built-up parts of Chennai and other cities needs to be pursued sincerely

Ahmedabad for instance, is credited with implementing an effective HAP, after a devastating heatwave with the mercury touching 46.8 degrees C in 2010 that killed over 1,340 people in a week. Cool roofs, which bring down temperatures by up to 3 degrees C (proven to reduce it even by 7 degrees C in Madrid, Spain), are one of the components of that plan, which has been modified in several iterations.

Make TN’s heat action plan work
Tamil Nadu’s HAP
calls for modification of existing buildings and walkways by giving them coatings to ward off intense heat. Even with such measures, the heat radiated by concrete structures is intense, raising demand for air-conditioning and putting staggering pressure on power availability. Passive cooling by painting buildings white is advocated for areas facing severe heat stress, and is a proven ancient intervention in the Mediterranean. Tamil Nadu could also look at newer passive cooling technologies that use nano materials embedded in film that reflect heat while themselves remaining cool. Such materials have been piloted for passive refrigeration among vegetable vendors in Karnataka.

Chennai’s large network of temple tanks have generally been neglected as water reservoirs, though the problem during some past years since 2015 has been an excess of water and flooding. A heat wave and drought would cripple Chennai’s competitiveness no less. If a massive drain infrastructure could be created in less than a year – it may still suffer maintenance deficits – a heat action plan can also achieve rapid progress.

According to the European Centre for Medium Range Weather Forecasts, wet bulb temperature is “the temperature recorded by a thermometer with its bulb covered by a wet cloth or wick. The greater the difference between the dry-bulb and wet-bulb temperature, the lower the humidity.”

Chief Minister M.K. Stalin could task the climate change department in the State with a time-bound implementation of the HAP in all high-stress areas, particularly heavily built-up cities and towns. An annual report on the HAP’s progress should be presented in the State Assembly.

Also Read: Power tariff hike should spur decentralised rooftop solar power in Tamil Nadu

While the El Nino of 2023 is yet to assert itself, it is widely expected to do so later this year, with a cascading impact in 2024. This is the clearest warning that weather scientists can give to political leaders and administrators, who generally tend to discount future disaster impacts and focus only on the present.

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