People sleep outside in Karachi, Pakistan amid sweltering temperatures, 18 May 2018. Photo: Akhtar Soomro / Reuters

By Jonathan Watts and Elle Hunt
13 August 2018

(The Guardian) – Imagine a city at 50C (122F). The pavements are empty, the parks quiet, entire neighbourhoods appear uninhabited. Nobody with a choice ventures outside during daylight hours. Only at night do the denizens emerge, HG Wells-style, into the streets – though, in temperatures that high, even darkness no longer provides relief. Uncooled air is treated like effluent: to be flushed as quickly as possible.

School playgrounds are silent as pupils shelter inside. In the hottest hours of the day, working outdoors is banned. The only people in sight are those who do not have access to air conditioning, who have no escape from the blanket of heat: the poor, the homeless, undocumented labourers. Society is divided into the cool haves and the hot have-nots.

Those without the option of sheltering indoors can rely only on shade, or perhaps a water-soaked sheet hung in front of a fan. Construction workers, motor-rickshaw drivers and street hawkers cover up head to toe to stay cool. The wealthy, meanwhile, go from one climate-conditioned environment to another: homes, cars, offices, gymnasiums, malls.

Asphalt heats up 10-20C higher than the air. You really could fry an egg on the pavement. A dog’s paws would blister on a short walk, so pets are kept behind closed doors. There are fewer animals overall; many species of mammals and birds have migrated to cooler environments, perhaps at a higher altitude – or perished. Reptiles, unable to regulate their body temperatures or dramatically expand their range, are worst placed to adapt. Even insects suffer. […]

Melting asphalt caused road markings to distort in New Delhi, during a 2015 heatwave. Photo: Harish Tyagi / EPA

At 50C – halfway to water’s boiling point and more than 10C above a healthy body temperature – heat becomes toxic. Human cells start to cook, blood thickens, muscles lock around the lungs and the brain is choked of oxygen. In dry conditions, sweat – the body’s in-built cooling system – can lessen the impact. But this protection weakens if there is already moisture in the air.

A so-called “wet-bulb temperature” (which factors in humidity) of just 35C can be fatal after a few hours to even the fittest person, and scientists warn climate change will make such conditions increasingly common in India, Pakistan, south-east Asia and parts of China. Even under the most optimistic predictions for emissions reductions, experts say almost half the world’s population will be exposed to potentially deadly heat for 20 days a year by 2100.

Not long ago, 50C was considered an anomaly, but it is increasingly widespread. Earlier this year, the 1.1 million residents of Nawabshah, Pakistan, endured the hottest April ever recorded on Earth, as temperatures hit 50.2C. In neighbouring India two years earlier, the town of Phalodi sweltered in 51C – the country’s hottest ever day.

Dev Niyogi, professor at Purdue University, Indiana, and chair of the Urban Environment department at the American Meteorological Society, witnessed how cities were affected by extreme heat on a research trip to New Delhi and Pune during that 2015 heatwave in India, which killed more than 2,000 people.

“You could see the physical change. Road surfaces started to melt, neighbourhoods went quiet because people didn’t go out and water vapour rose off the ground like a desert mirage,” he recalls.

“We must hope that we don’t see 50C. That would be uncharted territory. Infrastructure would be crippled and ecosystem services would start to break down, with long-term consequences.” […]

Children play in the water fountains at the Place des Arts in Montreal, Canada on a hot summer day 3 July 2018. Photo: Eva Hambach / AFP / Getty Images

At the Australian open in Melbourne this year – when ambient temperatures reached 40C – players were staggering around like “punch-drunk boxers” due to heatstroke. Even walking outside can feel oppressive at higher temperatures. “The blast of furnace-like heat … literally feels life-threatening and apocalyptic,” says Nigel Tapper, professor of environmental science at Melbourne’s Monash University, of the 48C recorded in parts of the city. “You cannot move outside for more than a few minutes.” [more]

Halfway to boiling: the city at 50C

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