Deadly Heat Waves Projected in South Asia by Late 21st Century, Study Finds

Extreme heat projected in South Asia could threaten the survival of some of the most vulnerable populations without significant mitigation to human-caused greenhouse gas emissions, according to a study co-authored by a Loyola Marymount University professor and published today in the journal Science Advances.

By the end of the 21st century (2071-2100), conditions in Pakistan, Nepal, India, Bangladesh and Sri Lanka – home to roughly one-fifth of the global human population – are likely to approach, and in some locations exceed, a human survivability threshold based on a combined measure of air temperature and humidity, the authors predict. Jeremy S. Pal, Ph.D., a professor of civil engineering and environmental science in LMU’s Frank R. Seaver College of Science and Engineering, conducted the research with Elfatih Eltahir, Sc.D., of the Massachusetts Institute of Technology, and Eun-Soon Im, Ph.D., of the Hong Kong University of Science and Technology.

A few hours of exposure to this so-called “wet-bulb temperature” of 95 F (or 35 C) – considered an upper limit on human survivability that is equivalent to a heat index of about 160 F – could result in death even for the fittest of humans in shaded, well-ventilated conditions, the study says.

“Without significant mitigation, some of the most severe hazards of climate change will impact some of the world’s most vulnerable populations, those who work outdoors in sectors such as agriculture as well as those who do not have access to air-conditioning,” said Pal, who published previous research with Eltahir projecting rising intolerable heat in the Persian/Arabian Gulf region by the end of the century.

“Affluent regions, such as the U.S. and Europe, have the financial means to cope with the adverse consequences of climate change,” he said. “However, poorer regions, where approximately 80 percent of the world’s population resides, do not necessarily have the capacity to adapt.”

In the current study, the researchers project that the most intense hazards from future heat waves will be concentrated around the densely populated Ganges and Indus river basins in northern India and Pakistan, agricultural regions where workers spend significant time outdoors. These areas are particularly susceptible due to the South Asian monsoon system that transports warm and humid air masses from the surrounding Arabian Sea and Bay of Bengal; their low elevations which keep temperatures warm; and irrigation, which increases humidity.

The study notes that India’s greenhouse gas emissions have been increasing rapidly in recent decades due to economic and population growth and high dependence on coal for energy generation. Despite relatively low greenhouse gas emissions per capita, “India (and more so China) is responsible for much of the recent rise in global emissions,” the study states.

The findings “may present a significant dilemma for India since continuation of the current trajectory of rising emissions will likely impose significant added human health risks to some of its most vulnerable populations,” the authors conclude.

The full study can be found here.