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Explained: Is India at risk of wet-bulb events?

India is predicted to face above normal temperatures this year, causing concern about scorching heatwaves and wet-bulb events. Also, what are wet-bulb events?

Most of India is projected to experience heatwaves from March to May. (Sanjeev Verma/HT Photo)(HT_PRINT)

By Aisiri Amin

LAST PUBLISHED 30.03.2023  |  05:30 PM IST

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On 29 March, Peter Dynes, chief strategy officer at Mirrors for Earth's Energy Rebalancing (MEER), a project which aims to directly address the threat of Earth's rising temperatures, tweeted that this summer might push India closer to the limits of human survival. “Rising temperatures are forecast in the coming weeks after India experienced its hottest February on record. The region is at serious risk of wet-bulb if global temperatures continue to rise," Dynes tweeted.

Earlier this month, the Indian Meteorological Department (IMD) stated that the country experienced its warmest February this year since 1877. Furthermore, the monthly average minimum temperature over the Indian region was the fifth highest in the last month since 1901. 

The rise in temperature across the world is a worrying trend that seems to be getting worse. A recent study published in Scientific Data found that India has contributed to 0.08 degrees Celsius of global warming from the 1850s to 2021 and ranks the nation as the fifth largest contributor to global warming among the top 10 countries analysed.

Also read: How to defuse the climate change time bomb

As the summer season approaches, the heat seems to be getting worse. The IMD warned that the majority of northeast, eastern, central, and portions of northwest India are likely to experience a summer with “above normal" temperatures. Most of India is projected to experience heatwaves from March to May, as reported by News18

Talking to Bloomberg last month, M Ravichandran, the top bureaucrat at the country’s earth sciences ministry said that India is likely to witness more extreme weather events, including intense heat waves, heavy flooding and severe drought that will impact food and energy security. Could these warnings and figures be pointing towards a summer that India is not prepared to face?

Amidst all the increasing warnings, the possibility of India facing wet-bulb temperatures is worrying. In a November 2022 report, the World Bank warned that India could become one of the first places in the world where wet-bulb temperatures could increase beyond the survivability threshold of 35°C. “The question is, have we got inured to heat-led suffering?" said Abhas Jha, one of the report’s authors, speaking to Bloomberg. “Because it's not a sudden onset disaster, because it's a slow onset, we don't push back on it."

Wet-bulb temperature is the lowest temperature to which air can be cooled by evaporation at a constant pressure. It is measured by wrapping a wet cloth around the bulb of a thermometer and the measured temperature corresponds to the wet bulb temperature, according to A.M.Y. Razak in the book, Industrial Gas Turbines. In simpler words, it’s the wet-bulb temperature that tells us at what point (considered to be above 35°C) our bodies would be unable to cool themselves through sweating, thus increasing the risk of fatal heatstroke.

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The 2022 Lancet Countdown report found that in India there was a 55% increase in deaths due to extreme heat. Deaths due to unbearable heat has led to one of the worst weather disasters in the past. In his Twitter thread, Dynes pointed out that one of the most severe wet bulb events was in Chicago in 1995 which resulted in the death of more than 700 people, mostly elderly and poor.

As seen in 1995, it’s the vulnerable sections that are most at risk and need support. However, the action plans to address heat waves currently do not take into account the impact on most vulnerable communities. The Centre For Policy Research (CPR), conducted the "first critical review" of heat action plans at the city (9), district (13) and state (15) levels across 18 states, as reported by the Press Trust of India.

The CPR report titled, ‘How is India adapting to heatwaves?’ showed that nearly all HAPs, or heat action plans, are poor at identifying and targeting vulnerable groups. “Only two of the 37 HAPs explicitly carry out and present vulnerability assessments. This leaves the implementer with little data on where to direct their scarce resources and could lead to poor targeting," CPR said in a statement.

Although solutions proposed by most HAPs do not necessarily focus on vulnerable groups, there was a need to integrate vulnerability assessments and ensure a holistic risk assessment where feasible, the report said. Excluding vulnerable communities from action plans can have an adverse impact and cannot be considered a solution-focused approach, the report added.

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