Under current climate change policies, billions will face life-threatening heat. But a global network of heat officers is tackling the problem in their own cities.
About 2 billion people will live in hazardous heat conditions by the end of the century if climate policies continue on their current trajectory, according to new research published in the Nature Sustainability journal. That represents 23% of the projected global population.
If the climate warms more drastically — a potential scenario under current policies — about 3.3 billion people could face extreme temperatures by the end of the century.
The study, led by scientists at the UK's University of Exeter and Nanjing University in China, found that 60 million people are already exposed to dangerous heat levels, characterized by an average temperature of 29 degrees Celsius (84.2 degrees Fahrenheit) or higher.
How do hot temperatures harm human health?
Extreme heat can result in a range of illnesses and death, according to the World Health Organization (WHO). These include heatstroke and hyperthermia. Temperature extremes also worsen chronic conditions and have indirect effects on disease transmission, air quality and critical infrastructure.
The elderly, infants and children, pregnant women, outdoor and manual workers, athletes and the poor are particularly vulnerable to higher temperatures.
Limiting warming to the lower Paris accord target of 1.5 degrees Celsius above pre-industrial levels would still expose 400 million people to dangerous heat levels by the end of the century, the study found.
People living in India, Sudan and Niger will all be heavily affected by even 1.5 degrees warming, but 2.7 degrees will have enormous effects on countries like the Philippines, Pakistan and Nigeria.
Calculating the human cost of climate change
Researchers said their study breaks the trend of modeling climate impacts in economic rather than human terms.
"It invariably distorts value away from human lives and towards centers of wealth," Ashish Ghadiali, a climate activist and co-author of the paper, told DW, adding that modeling focused on economics "places more value on a life in New York State than in Bangladesh."
Most other models also prioritize current populations over future ones, with inequality in global warming being "both globally distributed, but also intergenerational," said Ghadiali.
"It fundamentally values my life more than my children's lives and certainly more than my grandchildren's lives," he said.
Looking at individual country impacts on dangerous heat levels, researchers found that current emissions from 1.2 average US citizens condemn a future human to live in extreme heat. Despite having disproportionate emissions, the US population faces a much lower threat from dangerous temperatures.
