Scientists say increasing greenhouse gas emissions in densely populated parts of South Asia will push temperatures past the "upper limit on human survivability." They published their findings in the journal Science Advances.
The human body can only withstand so much heat, and the authors of the current paper note that 35°C (95°F) pushes that upper limit. Anything above that will result in death "even for the fittest of humans under shaded, well-ventilated conditions."
This 95°F maximum is what's called a wet bulb (TW) measurement. Like the heat index, TW considers humidity as well as air temperature, which means it's a more accurate measurement of how well our bodies can naturally cool themselves down. The muggier the climate, the higher the TW. And in places like India, the TW is pretty darn high.
The research team combined climate data from Pakistan, Nepal, India, Bangladesh, and Sri Lanka with information about current and estimated future greenhouse gas emissions in those countries.
With these combined data points, they created two possible scenarios: the "business as usual" model, in which the region's rapidly growing economy continues to produce more and more air pollution; and the "mitigation" model, in which something is done to slow, if not stop, emissions.
Neither outcome looked particularly good, but there was a big difference between them. The business-as-usual model indicated that average temperatures will easily reach TW 95°F by the year 2100. For the mitigation model, that number was closer to TW 88°F.
These were just the total averages. Some regions were far worse off than others. In either situation, poorer agricultural communities in India will be hit the hardest—a particularly dangerous outcome in areas where most people live without air conditioning.
"This disparity raises important environmental justice questions beyond the scope of this study," the authors write. "The findings … may present a significant dilemma for India because the continuation of this current trajectory of rising emissions will likely impose significant added human health risks to some of its most vulnerable populations."