India, Pakistan, Bangladesh and other parts of South Asia may experience heat waves, in which people cannot survive, by the end of this century if nothing is done to curb global warming, says a new study. “Business as usual runs the risk of having extremely lethal heat waves.”

The areas likely to be worst affected in northern India, southern Pakistan and Bangladesh are home to 1.5 billion people, said Eltahir, the study’s co-author. "The most intense hazard from extreme future heat waves is concentrated around the densely populated agricultural regions of the Ganges and Indus river basins," wrote the authors of the study, led by former MIT research scientist Eun-Soon Im, now an assistant professor at the Hong Kong University of Science and Technology. While most climate studies have been based on temperature projections alone, this one - published on Wednesday in the journal Science Advances - also considers humidity as well as the body's ability to cool down in response. So far, wet bulb temperatures have rarely exceeded 31 C (88-90 degrees F), a level that is already considered extremely hazardous. READ MORE: The case for collaborating on climate change

"What we see in this study is a convergence of intense weather projections and acute vulnerability," co-author and MIT environmental engineering professor Elfatih A.B. Heatwaves across South Asia in the summer of 2015 killed an estimated 3,500 people and similar events will become more frequent and intense, researchers said. “Officials know more people are coming and they’re trying to figure out how to deal with that.”

While Florida and the southeast states will also face more extreme heat, America’s dangerous heat zone is in the middle of the country from Minnesota, along the Mississippi River Valley to New Orleans, said Richard Rood, a meteorologist and climate expert at the University of Michigan. Researchers behind the study, published in the journal Science Advances, found that 4% percent of the South Asian population is expected to experience temperature and humidity conditions in which humans cannot survive without air conditioning by 2100.
New research suggests that large parts of Southern Asia may be uninhabitable by 2100 due to levels of humidity dangerous to humans.