Global warming breaching three degrees Celsius will affect older adults in India, China, Pakistan, and Bangladesh, accounting for 1.5 billion people, or 73 per cent of the total affected population worldwide, a new study published in The Lancet Planetary Health journal has projected.
The study focuses more on the old age population and claims that intolerable heat will be experienced at much larger scales and for longer durations, affecting far more people than previously estimated.
Older adults in south Asia and the Persian Gulf could face sustained, day-and-night exposure for three consecutive months at 3°C or more warming, researchers said.
They are less able to regulate their body temperature under high temperatures and humidity as they tend to sweat less, their blood vessels respond more slowly, and their hearts work harder in the heat.
The number of people aged 60 years and older is projected to double from 1 billion in 2020 to 2·1 billion in 2050, representing 21% of the world’s population.
More than two-thirds of this population is expected to reside in low-income and middle-income countries, many of which are also on the frontline of emerging uncompensable heat stress (UHS).
The researchers drew on previously published laboratory experiments that measured heat tolerance separately for three age groups - younger adults (15-39), middle-aged adults (40-59), and older adults (60 and over).
They then mapped where heat would become dangerous for each age group, and how many people would be affected, using a high-resolution heat stress metric across different scenarios ranging from one to four degrees Celsius of global warming above pre-industrial levels, combined with population projections.
"India, China, Pakistan, and Bangladesh together account for 1.48 billion exposed individuals, representing 72.6 per cent of the 2.03 billion global total exposed population," the authors wrote.
The study provides new empirical uncompensable heat limits for middle-aged and older adults, they said.
Accounting specifically for the age vulnerability was found to substantially increase the magnitude and spatial extent of projected risk, compared to those reported in previous studies.
"Older adults face far more frequent and widespread uncompensable heat, having greater heat risk under 1.5 degrees Celsius of global warming than young adults do under 4 degrees Celsius," the authors wrote.
Intolerable heat is likely to affect far more people, across larger regions, and for durations longer than previously recognised, they said.
Heatwaves in UK, Europe
The UK Health Security Agency had recently said that it fears that 2026’s high temperatures in Britain – parts of which have experienced five heatwaves – are likely to mean that the country records its highest ever number of heat-related deaths in a year.
The four-day heatwave in May and eight-day heatwave in June together caused 2,877 excess deaths, almost double the 1,504 seen during the summer of 2025.
The record-breaking heatwaves across the UK and Europe this summer have also inflicted substantial economic costs.
A UK-based think tank Verdant estimates the heatwaves have cost the country's economy at least £4.4 billion in lost output since the extreme weather started in May.
And the second by the Triodos Bank estimates that the extreme summer weather could reduce EU GDP approximately €180 billion and would effectively erase the growth previously forecast for the year.
The Verdant analysis also claims cumulative losses from heatwaves will reach £25.6 billion by 2030 if they continue to intensify.
