India’s deadly heat waves are getting even hotter
The consequences of climate change will be horrific for the Indo-Gangetic Plain Apr 2nd 2023 | DELHI AND JACOBABAD heat waves in India In the opening scenes of “The Ministry for the Future”, the novelist Kim Stanley Robinson imagines what happens to a small Indian town hit by a heat wave. Streets empty as normal activity becomes impossible. Air-conditioned rooms fill with silent fugitives from the heat. Rooftops are littered with the corpses of people sleeping outside in search of a non-existent breath of wind. The electricity grid, then law and order, break down. Like a medieval vision of hell, the local lake fills with half-poached bodies. Across north India, 20m die in a week. Mr Robinson said he wrote his best-seller, published in 2020, as a warning. The Indo-Gangetic Plain, which extends from the spine of Pakistan through northern India to the deltas of Bangladesh, is home to 700m people and exceptionally vulnerable to the heat pulses that climate change is making more frequent. It is one of the hottest, poorest and most populous places on earth (see map). Its electricity grids are unreliable. Between 2000 and 2019, South Asia saw over 110,000 excess deaths a year due to rising temperatures, according to a study in Lancet Planetary Health, a journal. Last year’s hot season, which runs from March until the arrival of the monsoon in late May or early June, was one of the most extreme and economically disruptive on record. This year’s could rival it. India has just experienced its hottest December and February since 1901. In March the India Meteorological Department (imd) and its counterpart in Pakistan (pmd) warned of above-average temperatures and heatwaves until the end of May. On March 6th Narendra Modi, India’s prime minister, chaired a review on hot season preparedness. Pakistan’s National Disaster Management Authority has kicked off a countrywide simulation to test emergency responses to the flooding that can follow extreme heat. Despite a relatively cool March, the coming weeks could be perilously hot. On April 1st Mrutyunjay Mohapatra, imd’s chief, sounded the alarm again. Scientists record heat stress as a combination of temperature and humidity, known as a “wet-bulb” measurement. As this combined level approaches body temperature, 37°C, it becomes increasing hard for mammals to shed heat through perspiration. At a wet-bulb temperature of around 31°C, dangerously little sweat can evaporate into the soup-like air. Brain damage and heart and kidney failure become increasingly likely. Sustained exposure to a temperature of 35°C, the level Mr Robinson imagines in his book, is considered fatal. The Indo-Gangetic Plain is one of the few places where wet-bulb temperatures of 35°C have been recorded, including on several occasions in the scorched Pakistani town of Jacobabad. A report by the World Bank in November warned that India could become one of the first places where wet-bulb temperatures routinely exceed the 35°C survivability threshold. The regular temperature last year peaked in Jacobabad, which sits at the border of Pakistan’s provinces of Sindh and Balochistan, at 51°C. Half the town’s population of 200,000 had by then fled in search of more bearable temperatures. Even after the temperature began to ease, in early June, it was hard to resume regular activity. Ali Bahar, a daily-wage labourer in Jacobabad, recalls trying and failing to work in its surrounding fields in June. While driving a tractor in 42°C heat, he felt feverish and dizzy, then tumbled from the machine, injuring his head. Co-workers carried him to a local clinic, which dished out the standard treatment of a packet of orange-flavoured rehydration salts. Though he was discharged six hours later, he was unable to work for a week. The temperature record provides a horrifying account of the changes afoot. According to the definition of a heat wave used by India’s weather agency, which takes into account average annual local temperatures and the duration of the anomaly, India saw, on average, 23.5 heatwaves every year in the two decades to 2019, more than double the annual average of 9.9 it saw between 1980 and 1999. Between 2010 and 2019, the incidence of heatwaves in India grew by a quarter compared to the previous decade, with a corresponding increase in heat-related mortality of 27%. During last year’s hot season, India experienced twice as many heatwave days as in the same period in 2012, the previous record year. Climate change made last year’s heat pulse 30 times likelier than it would otherwise have been, according to World Weather Attribution, a global research collaboration. That is both because it has raised India’s average annual temperature—by around 0.7°C between 1900 and 2018—and because it has made anomalous heat surges bigger and more frequent. The magnifying effect of the built urban environment, which can be 2°C hotter than nearby rural areas, is often especially pronounced in India’s concrete jungles. Those living in slum housing, which offer little air circulation and often use heat-sucking materials such as tin, suffer the worst of it. If the climate warms by 2°C compared with pre-industrial levels, as appears unavoidable, such events would be more likely by an additional factor of 2-20. Even if the world makes more headway on curbing greenhouse-gas emissions than looks likely, “vast regions of South Asia are projected to experience [wet-bulb temperature] episodes exceeding 31°C, which is considered extremely dangerous for most humans”, according to a paper by Elfatih Eltahir of the Massachusetts Institute of Technology and colleagues. The costs of crippling heat are already vast. Even working in the shade on an average summer day in Delhi results in labour losses of 15-20 minutes per hour at the hottest times, reckons Luke Parsons of Duke University in North Carolina. Mr Parsons and colleagues have estimated that India loses 101bn man hours per year to extreme heat, and Pakistan 13bn. During last year’s withering hot season, the wheat harvest was down by around 15% in both countries—and in some regions by as much as 30%. Livestock perished. The normal agricultural day became impossible. Electricity outages, in
