The Red Cross and the United Nations warned on Monday that heat waves will become so extreme in certain regions of the world within decades that human life there will be unsustainable, as they urged people and governments to do more to beat the heat by preparing better for heat waves like recent ones ranging from Sacramento, California, to Somalia and Sichuan, China.
Heat waves are predicted to "exceed human physiological and social limits" in the Sahel, the Horn of Africa and South and Southwest Asia, with extreme events triggering "large-scale suffering and loss of life," the organizations said.
Heat wave catastrophes this year in countries like Somalia and Pakistan foreshadow a future with deadlier, more frequent and more intense heat-related humanitarian emergencies, they warned in a joint report.
The U.N.'s Office for the Coordination of Humanitarian Affairs (OCHA) and the International Federation of Red Cross and Red Crescent Societies (IFRC) released the report in advance of next month's U.N. Climate Change Conference (COP27) climate change summit in Egypt.
"We don't want to dramatize it, but clearly the data shows that it does lead towards a very bleak future," said IFRC secretary-general Jagan Chapagain.
They said aggressive steps needed to be taken immediately to avert potentially recurrent heat disasters, listing steps that could mitigate the worst effects of extreme heat.
"There are clear limits beyond which people exposed to extreme heat and humidity cannot survive," the report said.
"There are also likely to be levels of extreme heat beyond which societies may find it practically impossible to deliver effective adaptation for all.
"On current trajectories, heat waves could meet and exceed these physiological and social limits in the coming decades, including in regions such as the Sahel and south and southwest Asia."
It warned that the impact of this would be "large-scale suffering and loss of life, population movements and further entrenched inequality."
The report said extreme heat was a "silent killer," claiming thousands of lives each year as the deadliest weather-related hazard – and the dangers were set to grow at an "alarming rate" due to climate change.
According to a study cited by the report, the number of poor people living in extreme heat conditions in urban areas will jump by 700% by 2050, particularly in west Africa and southeast Asia.
"Projected future death rates from extreme heat are staggeringly high – comparable in magnitude by the end of the century to all cancers or all infectious diseases – and staggeringly unequal," the report said.
Agricultural workers, children, the elderly and pregnant and breastfeeding women are at higher risk of illness and death, the report claimed.
"As the climate crisis goes unchecked, extreme weather events, such as heat waves and floods, are hitting the most vulnerable people the hardest," said U.N. humanitarian chief Martin Griffiths.
"The humanitarian system is not equipped to handle crises of this scale on our own."
Chapagain urged countries at COP27 to invest in climate adaptation and mitigation in the regions most at risk.
The OCHA and the IFRC suggested five main steps to help combat the impact of extreme heat waves, including providing early information to help people and authorities react in time, and finding new ways of financing local-level action.
They also included humanitarian organizations testing more "thermally appropriate" emergency shelters and "cooling centers," while getting communities to alter their development planning to take account of likely extreme heat impacts.
OCHA and the IFRC said there were limits to extreme heat adaptation measures.
Some, such as increasing energy-intensive air conditioning, are costly, environmentally unsustainable and contribute to climate change.
If emissions of greenhouse gases that cause climate change are not aggressively reduced, the world will face "previously unimaginable levels of extreme heat."
