The big cities where it’s getting too hot for people to live

Large areas of Earth’s surface could soon be so hot that people will die within hours in the open air, several recent studies have warned

With record-breaking temperatures being recorded seemingly every month, experts are now warning large areas of the Earth could become completely inhospitable to humans due to the scorching heat.

January was the world’s warmest on record, despite a shift towards the La Niña weather pattern that should have resulted in cooler weather.

Instead, January’s temperatures extended a run of extraordinary heat, in which 18 of the last 19 months saw an average global temperature of more than 1.5C above pre-industrial times. Scientists described the results as “surprising”.

The impact of increasingly extreme temperatures on humans could eventually result in swathes of currently habitable areas becoming so inhospitable that people are simply unable to live there because of the heat.

Some experts warn that some areas of the Middle East could soon be at risk, with some regions of China, Brazil and the United States potentially at risk further into the future.

The resulting upheaval could lead to increased mass migration and even spark wars over water and food supplies, experts have warned.

Aidan Charron, an environmental scientist and associate director of Earth Day, warned that the warning signs of extreme heat are already here.

“Parts of South Asia, sub-Saharan Africa, and the Middle East – Dubai for example in the United Arab Emirates – are all going to face some of the worst impacts of climate change in the form of even worse extreme heat indexes,” Carron told Yahoo News.

In May 2024, India and Pakistan also saw record heat waves with temperatures hitting 50C.

“This is all going to get worse,” Carron continued. “New Delhi was especially badly hit with extreme heat. We could easily see heat indexes in this part of the world that make outdoor life virtually impossible, by the end of the century. In the US too this is going to be an issue – for example, Chicago is becoming a severe heat zone.”

Some of the most populous areas in the world in Africa and South-east Asia are most at risk.

Previous research showed that Yemenese cities such as Hudaydah could experience up to 56 days a year of intolerable heat, while Aden would have 34 days.

Jeddah in Saudi Arabia would have 37 days, and Lahore in Pakistan would have 24, while Dubai would have 20 and Delhi would have six.

“Already in Iraq and Syria, droughts have been linked to heightened social tensions and mass migration,” Charron said. “By 2050, parts of the Middle East could experience up to 30% less precipitation, turning areas that were once fertile into deserts.

“These people won’t stay and die, they will migrate north. We could easily see the precious resources of clean water and fertile soil being fought over.”

The worries of ‘wet bulb temperatures’
Human beings can survive very high temperatures (well over 50C) when humidity is low, but in high humidity, we cannot survive temperatures of even 35C for long periods, because there is no way to cool down by sweating.

In such circumstances, even the fittest people can die within hours in the most extreme conditions.

In the coming decades, a measurement called ‘wet-bulb temperature’ – the lowest temperature to which an object can cool down when moisture evaporates from it – could become crucial for determining which areas of our warming planet remain habitable.

Wet-bulb temperature is measured by taking the temperature from a thermometer covered in a wet cloth, which is normally slightly cooler than ‘dry-bulb temperatures’.

This allows researchers to work out whether humans can sweat in such temperatures: if the water evaporates, the thermometer cools down, so that ‘wet bulb’ temperatures are lower than ‘dry bulb’ temperatures.

Climatologist Dr Jennifer Brandon, founder of Wild Beacon Consulting, told Yahoo News: “In terms of areas that will be too hot to be considered liveable, we often look at what we call the ‘wet bulb temperature’.

“Basically, it measures how our bodies cool down from sweating. Think about getting out of a hot shower. If the room is cooler, you cool down quickly. If the room is hot and humid, you cool down much slower.”

“The fear in a heating world is that our bodies can never fully cool down, and so risks of heat stroke and heat exhaustion increase as the wet bulb temperature increases.

“The highest wet bulb temperature that humans can survive is 35C for about six hours. The places people predict are most vulnerable for being that hot, and thus becoming unliveable are South Asia, the Persian Gulf and the Red Sea by around 2050, and Eastern China, parts of Southeast Asia, and Brazil by 2070.”

How bad could things get?
A study this year measured both ‘uncompensable’ thresholds, where body temperature rises uncontrollably, and ‘unsurvivable’ thresholds where the body’s core temperature rises to 42C within six hours.

‘Uncompensable’ means that humans cannot cool down by sweating, and ‘unsurvivable’ means that temperatures would be fatal to adults within hours.

If the world’s temperature rises by up to 4-5C above pre-industrial levels, older people could experience uncompensable heat across 60% of Earth’s surface during heat wave events.

The Climate Action Tracker predicts that today’s policies could lead to 2.7C warming above pre-industrial levels by 2100: warming of 4-5C is unlikely, but not impossible.

With a rise of this level, unsurvivable heat would also begin to affect younger people in tropical areas, the King’s College study found.

With a rise of 2C, the area where even young adults could not keep a safe body temperature will triple to 6% of Earth’s land surface.

Credit: Yahoo News