If you thought that this year’s heat wave in the early summer months followed by the oppressive humidity of the monsoon months was a one-off bad year occurrence then think again. New research shows unchecked global warming is exposing millions of people living in India and the South Asian region to dangerous levels of heat and humidity.Without aggressive and concrete efforts to curb carbon dioxide pollution, most of India, Pakistan, and Bangladesh will by the end of the century experience temperature levels well beyond those considered safe for humans. It projects that 4% of the population will experience temperature and humidity conditions in which people cannot survive without air conditioning. The majority of the population, 75%, will experience temperature levels that are considered as dangerous or unliveable.The study, authored by MIT’s Elfatih Eltahir of MIT and Jeremy Pal of Loyola Marymount University, both professors of environmental engineering along with Eun Soon Im of the Hong Kong University of Science and Technology, uses the concept of human survivability threshold based on wet bulb temperature.Wet bulb temperature is a combined measure of temperature and humidity. This measure is critical for humans. Normal temperature inside human bodies is 37°C, and normal body skin temperature is 35°C. Therefore, a wet-bulb temperature of 35°C is considered as the upper limit of human survivability in natural conditions.This map shows the maximum wet-bulb temperatures (which combine temperature and humidity) that have been reached in this region since 1979.An increase in the wet bulb temperature beyond 35°C reduces the human body’s ability to cool itself and can immediately impair physical and cognitive functions. Exposure to wet bulb temperatures of 35°C or more for even a few hours will result in death even for the fittest of humans under shaded, well-ventilated conditions.The study, published in the journal Science Advances this week, finds that these deadly heat waves and high humidity levels could reached within a few decades. It also finds that the most intense hazard from extreme future heat waves is concentrated around densely populated agricultural Indo-Gangetic river basins.The projected temperature rise would make it impossible for people to stay and work outdoors for extended periods of time. The economic fallout is immense since the large majority of the population depends on agriculture for their livelihoods. The decline in agricultural output will endanger the region’s food security. The most vulnerable and those least responsible for climate change will have to bear the brunt.“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.“Affluent regions, such as the US and Europe, have the financial means to cope with the adverse consequences of climate change,” he said. “However, poorer regions, where approximately 80% of the world’s population resides, do not necessarily have the capacity to adapt.”The study, based on detailed computer simulations, stresses that the direst of consequences can be averted with aggressive efforts to curb emissions. Projections show that achieving the Paris Agreement goal of restricting temperature rise to well below 2°C would mean that 2% of the population would be exposed to temperature levels considered to be dangerous, that is a wet bulb temperature of more than 31°C.For countries like India, the findings of the study drive home both the dilemma and the urgency of tackling global warming. India’s emissions are set to rise driven by economic growth necessary to pull out its millions still living in poverty. At the same time, business as usual development will endanger the lives of its people, especially those who are least equipped to take measures to mitigate against rising temperatures.Even as India continues to push for greater global action to curb emissions, it must step up its transition to low-carbon development given that India is home to one of the hotspots of climate change impact.