A Fifth of the World Could Live With Dangerous Heat by 2100, New Study Warns

Most people live in a place with a mean annual temperature of 55 to 80 degrees Fahrenheit. But billions of people could see that figure jump to 84 degrees or higher, research says.

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A man dumps water on his head from a Municipal Water Tanker to cool himself outside a slum cluster on a hot summer day in New Delhi, India on May 23, 2023. Credit: Kabir Jhangiani/NurPhoto via Getty Images
A man dumps water on his head from a Municipal Water Tanker to cool himself outside a slum cluster on a hot summer day in New Delhi, India on May 23, 2023. Credit: Kabir Jhangiani/NurPhoto via Getty Images

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One in five people could live in dangerously hot conditions by the end of the century if global warming continues at its current pace, even if nations uphold their pledges under the Paris Agreement, scientists warned in a new peer-reviewed study. It’s the latest research published in recent days that points to the stark human and societal costs of the accelerating climate crisis as global carbon emissions continue to rise to unprecedented levels.

The study, published Monday in the journal Nature Sustainability, estimates that some 2 billion people would see a mean annual temperature of 84 degrees Fahrenheit or higher, starting in as early as 2070, when Earth’s population is expected to reach at least 9.5 billion. Most people live in a “human climate niche” that ranges between a mean annual temperature of 55 degrees and 80 degrees, the researchers said, so that many people experiencing a major uptick in regional heat would be unprecedented.

Such a temperature threshold, where 84 degrees or higher becomes the middle ground for the year, can also be very dangerous for anyone without air conditioning or other means to cool off, the study’s authors also noted. According to their estimate, some of the nations that will be hardest hit by the heat are also home to some of the world’s poorest communities, where air conditioning typically isn’t an option.

Of the estimated 2 billion people that could be forced out of their climate niche and into dangerous extreme heat, the study found, 600 million will be in India, 300 million in Nigeria and 100 million in Indonesia.

“Those people who are affected are the poorer people on the planet,” Tim Lenton, director of the Global Systems Institute at Exeter and the study’s lead author, told Forbes. “At higher temperatures, life becomes unbearable, affecting water, agriculture and food. You can’t barricade yourself from climate change. There is an undeniable interconnection amongst nations.”

Among the study’s most pertinent findings is the drastic difference it would make for the world to limit average warming to just 1.5 degrees Celsius above pre-industrial levels—the most ambitious target of the Paris Agreement. Scientists estimate that under the global climate treaty’s current pledges, the world is still on track to warm by roughly 2.7 degrees Celsius by 2100. But if emissions were significantly slashed to limit average warming to 1.5 degrees, Monday’s study said, just 400 million people would be pushed outside their climate niche instead of 2 billion.

Monday’s study also comes on the heels of a major report released last week by the United Nations’ weather agency, which warned that heat will likely soar to record levels in many parts of the world over the next five years. Global warming, combined with a climate pattern known as El Niño, will largely drive that heat, the report’s authors said, with the next five years almost certainly set to be the warmest five-year period ever recorded.

“This will have far-reaching repercussions for health, food security, water management and the environment,” Petteri Taalas, the World Meteorological Organization’s secretary general, told the New York Times. “We need to be prepared.”

It’s not just extreme heat that climate scientists have warned about in recent days.

On Monday, the World Meteorological Organization released another report, which found that the economic damage of natural disasters continues to rise, even as improvements in early warning systems have helped reduce the loss of life. In that report, the U.N. body tallied nearly 12,000 extreme weather, climate and water-related events globally between 1970 and 2021 that have killed more than 2 million people and caused $4.3 trillion worth of economic damage.

And climate change is already affecting all parts of the world, not just the poorer regions. About $1.7 trillion of that financial damage took place in the United States alone.

The new studies and reports, in many ways, are pointing to a reality with which many people are already familiar. This week, swathes of India are baking under extreme heat, with some places reaching temperatures as high as 113 degrees Fahrenheit on Monday. Over the weekend, raging wildfires in Canada continued to send smoke south into the U.S., prompting officials in Colorado and Montana to issue air quality alerts. And last week, heavy rainfall inundated 43 towns in Italy, causing landslides and flash floods that killed 14 people and destroyed hundreds of roads.

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Today’s Indicator


That’s how many hours of sleep humans are losing every year on average as climate change drives warmer nighttime temperatures, according to a new study. Sleep loss was especially prominent in lower-income and elderly communities, it found.

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