In his best-selling 2020 novel, The Ministry for the Future, science fiction writer Kim Stanley Robinson opens with a deadly heatwave in India which kills millions of people.

The sky blazes like an "atomic bomb", the heat from it is a "slap in the face", the eyes sting and "everything was tan and beige and a brilliant, unbearable white". Water doesn't help because it is "hot as a bath… worse than the air". People die "faster than ever".

Mr Robinson's dystopian tale about global heating might be a horror fantasy of sorts, but it is also a chilling warning. Earlier this week, 12 people died from heatstroke and many others were admitted to hospital after attending a government-sponsored event in an open ground under a blazing sun in Navi Mumbai in India's Maharashtra state.

India is one of the countries most exposed and vulnerable to heat. Hot days and hot night events have risen significantly, and are projected to increase between two and four-fold by 2050. Heatwaves are also predicted to arrive earlier, stay longer and become more frequent.

The weather office has predicted above-average temperatures and heatwaves until the end of May. Average temperatures in India have risen by around 0.7% between 1901 and 2018, partly due to climate change.

Heatwaves killed more than 22,000 people between 1992 and 2015, according to official figures. Experts reckon the actual toll would be much higher. Yet, the country really "hasn't understood the importance of heat and how heat can kill", says Dileep Mavalankar, director of the Gujarat-based Indian Institute of Public Health. "This is partly because we don't compile our mortality data properly."

Prof Mavalankar should know. In May 2010, he found that the city of Ahmedabad had recorded 800 all-cause excess deaths - a measure of how many more people are dying than expected, compared to the previous few years - during a sweltering week of record-breaking temperatures. It was clear, he said, that heat was killing a lot of people. He said researchers compared the total number of deaths in the city to the maximum temperature recorded on the day, and laid down three colour coded alerts, with the red warning triggering above 45C.

Prodded by these findings, Prof Mavalankar helped put together India's first heat action plan for the city of Ahmedabad. The plan kicked off in 2013 and advocated simple solutions like staying indoors, drinking lots of water before stepping out, and going to the hospital emergency if one felt sick. By 2018, he says, deaths from all causes had declined by a third in the hot, dry city.

But the bad news is India's heat action plans don't seem to be working very well. (It is unclear whether the authorities in Navi Mumbai had a heat action plan in place when a million people reportedly were allowed to gather under the open sky.) A new study of 37 heat action plans at the city, district and state levels by Aditya Valiathan Pillai and Tamanna Dalal of Centre for Policy Research, a think-tank, found a lot of shortcomings.

For one, most of the plans were not "built for local context and have an oversimplified view of the hazards". Only 10 of the 37 plans studied seem to establish locally defined temperature thresholds, although it was unclear whether they took factors like humidity into account while declaring a heatwave. "We recommend nuancing and localising the heat hazard definition by including climate projections," Mr Pillai told me. One way to do it is to have more automated weather stations at village levels, according to Prof Mavalankar.

Second, the researchers found that nearly all the plans were poor at "identifying and targeting vulnerable groups". Farm and construction workers who toil in the open, pregnant women, the elderly, and children were most vulnerable to heat.

Some three-fourths of India's workers work in heat-exposed jobs like construction and mining. "Workers are losing the ability to safely and efficiently work outside as the planet warms. It's becoming too hot and humid for them to cool themselves enough when they generate a large amount of body heat when conducting heavy labour," says climate researcher Luke Parsons of Duke University, North Carolina.

This becomes worse during heatwaves as there are fewer safe and productive work hours during the day, he adds.

Mr Pillai says that India needs "granular understanding of which neighbourhoods have most people working in jobs where they are exposed to heat and whether they could afford to buy a cooler or afford to skip work". He adds: "You might have a situation where 3% of the area of the city contained 80% of the vulnerable population."

Also most of the heat action plans seem to be underfunded, had weak legal foundations with scant accountability, and were not sufficiently transparent, Mr Pillai and Ms Dalal found.

Heatwave solutions can often be simple - planting enough trees in extremely exposed and hot areas or using design choices to reduce heat gain and increase heat loss in buildings.

Sometimes simple surveillance solutions such as moving patients from a baking top floor to a lower floor of a non-airconditioned hospital can protect lives, as a study in Ahmedabad found. Having worker protections in place to stop or slow work if it is too hot can help so people don't feel the need to keep working at high intensity when it's not safe, says Mr Parsons.

India saw a 55% rise in deaths due to extreme heat between 2000-2004 and 2017-2021, a recent study published in the medical journal, The Lancet, found. Exposure to heat also caused a loss of 167.2 billion potential labour hours among Indians in 2021, resulting in loss of incomes equivalent to about 5.4% of the country's GDP.

But clearly, Indians are still not taking heat seriously enough.

According to reports, the place in Navi Mumbai where the government ceremony had taken place had recorded a maximum temperature of 38C (100F) on Sunday. Yet, photos of the event showed thousands sitting directly under the sun with no roof or covering to offer shelter. Only a few carried umbrellas, or wrapped towels on their heads.

"I live in Delhi where the temperature can touch 50C and I see very few people even bring out their umbrellas," Mr Pillai says.

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