New Delhi: 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.
Older people could face serious health risks from heat at lower temperatures than previously estimated, it found.
South Asia and the Persian Gulf regions are shown to be the most exposed, where older adults could face a dangerous heat day and night for three months straight once warming reaches three degrees Celsius or above, researchers, including those from Stanford and The Pennsylvania State universities, said.
The greatest challenge is projected to fall on countries that combine a high heat exposure with high poverty rates and a limited access to cooling, including India, Pakistan, Bangladesh, Myanmar, and Niger.
Older adults 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 researchers said previous research relied heavily on measurements from healthy young adults to estimate when temperatures and associated humidity would become challenging for the human body.
Previous studies may have underestimated the number of older adults at risk from extreme heat by at least twice, they said.
The study accounts for age-related differences in heat tolerance on a global scale, the team said.
They 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).
The researchers then mapped where heat would become dangerous for each 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.
