Living in hothouse India: We have entered a new age of heat extremes. Concrete and glass-heavy urban buildings are a major hazard

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Context: India is searing. Large parts of the country are in the grips of unbearable heat and heatwaves. It’s not supposed to be like this in March and April. Such heat is usually expected in May and June – the year’s hottest months.

But this temperature anomaly is not unexpected.

In fact, various IPCC reports point to heatwaves becoming a major calamity in the coming years.

What is the situation wrt heatwaves in India?

March 2022 was the hottest March on record, and March-April has witnessed a record number of heatwaves.

Delhi has recorded eight heatwave days in April so far, and the maximum temperature in parts of the city has already hit 43-45°C, which is 5-7°C above normal.

Both temperatures and heatwaves have been increasing perceptibly since the 1980s. Each of the last four decades has been progressively warmer than the decade that preceded it.

The past decade (2011-20) was the hottest since records began in 1901, and 11 out of 15 warmest years were between 2007 and 2021.

Likewise, the heatwave days have also increased every decade since 1980.

In addition, the hotspots of intense heatwaves have expanded. They now engulf a large part of the country, hitting areas that were not prone to extreme heat events in the past, like Himachal Pradesh, Andhra Pradesh, Tamil Nadu and Karnataka.

In fact, there has been an alarming increase in severe heatwaves in southern India. The problem is that south India also experiences high humidity. This means that in the pre-monsoon period, when the humidity is usually high, a heatwave could push the “wetbulb” temperature (that measures the combined effect of temperature and humidity) beyond 35°C.

Few humans can tolerate it for a long time because their bodies can’t cool themselves.

According to the latest IPCC report, the intensity and frequency of heatwaves will increase with every increment of warming.

The report also points out that the Indian subcontinent will be hardest hit by deadly heatwaves.

What are the possible steps that need to be taken?

Mitigation is the best adaptation. Global warming needs to be limited to 1.5 °C. Several mitigation options – solar and wind energy, energy efficiency, the greening of urban infrastructure, demand-side management etc.

Building cities that cool themselves: The urban heat island effect increases the severity of heatwaves. City centres are now a few degrees warmer than the hinterlands because of the large amounts of heat emitted from our buildings, roads, factories and cars. To combat outside heat, more and more ACs are being installed, thereby unleashing a vicious cycle of spiralling heat island effect.

This cycle can be broken only by building cities that cool themselves. This means more open spaces, green areas and water bodies, and more energy-efficient green buildings.

Changing our laws: Most modern buildings are built with too much concrete, glass and poor shading and ventilation, making them prone to overheating. Therefore, our building bye-laws, urban planning guidelines and construction technologies must be radically changed to adapt to the rising heat.

A new heat code: India needs a new heat code. Many regions of the country now experience wet-bulb temperatures exceeding 31°C during certain parts of the year, which is dangerous for manual labour. However, we are not declaring such days as heatwaves because our guidelines are based on dry-bulb temperature. Therefore, we need a heat code that outlines the criteria for declaring heatwaves based on wet-bulb temperature. It should also prescribe SOPs for heatwave emergencies, such as work-hour limits and relief measures in public places and hospitals.

Way forward

Heatwave is theoretical discomfort for some of us who move from an airconditioned home to an air-conditioned car to an air-conditioned office.

But it is a matter of life and death for a poor person dependent on manual labour and living in a hothouse in an urban slum or a village.

India, therefore, needs a heat action plan that saves the majority from hot extremes.

Source: This post is based on the article “Living in hothouse India: We have entered a new age of heat extremes. Concrete and glass-heavy urban buildings are a major hazard” published in The Times of India on 24th Apr 22.

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