India Pushed Closer To The Limit Of Human Survival Amid Record Heat Waves

"India is typically more humid than equivalently hot places, like the Sahara. This means sweating is less efficient, or not efficient at all," said Kieran Hunt.

India, on course to becoming the world's most-populous country, risks approaching the limit of human survival as it experiences more intense and frequent heat waves.

The national weather office has forecast rising temperatures in the coming weeks after India experienced its hottest February since 1901. That's stoked concerns that there will be a repeat of last year's record heat wave, which caused widespread crop damage and triggered hours-long blackouts. While temperatures as high as 50 degrees Celsius (122 Fahrenheit) are unbearable in any condition, the damage is made worse for those of India's 1.4 billion population who are stuck in tightly packed cities and don't have access to well-ventilated housing or air-conditioning.

"Heat stress for humans is a combination of temperature and humidity," said Kieran Hunt, a climate scientist at the University of Reading who has studied the country's weather patterns. "India is typically more humid than equivalently hot places, like the Sahara. This means sweating is less efficient, or not efficient at all."

This is why in India a measurement known as the wet-bulb reading - which combines air temperature and relative humidity - provides a better gauge of heat stress on the human body. A November report by the World Bank cautioned that India could become one of the first places in the world where wet-bulb temperatures could soar past 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. "Because it's not a sudden onset disaster, because it's a slow onset, we don't push back on it."