Extreme heatwaves that can kill healthy people within hours will start striking parts of Pakistan, India and Bangladesh unless global carbon emissions are cut drastically, according to the new research. Scientists at the Massachusetts Institute of Technology (MIT) found that densely-populated areas in the Indus and Ganges river basins will be the worst affected, leading to reduced crop yields. “Climate change is not an abstract concept, it is impacting huge numbers of vulnerable people,” MIT professor Elfatih Eltahir told the Thomas Reuters Foundation. “Business as usual runs the risk of having extremely lethal heat waves.” The study, published in Science Advances, used state-of-the-art climate models to project potential future heat and humidity in South Asia, already the warmest region in the world. While most climate studies have been based on temperature projections alone, this one also considers humidity as well as the body’s ability to cool down in response. Researchers considered three factors that make up what is called a “wet-bulb temperature”, which is the air temperature taken when a wet cloth is wrapped round the thermometer. Human beings can survive a wet-bulb temperature of up to 35 degrees Celsius. Beyond which, the human body will have difficulty cooling down, leading to heat stroke and eventually death. Those most at risk are poor farmworkers or outdoor construction labourers in India, Pakistan and Bangladesh where they are least likely to have air conditioners. Some 25 per cent of India’s population still has no access to electricity. About 15 per cent of India’s population gets exposed to those extreme temperatures of 31 or 32 C but under the business-as-usual model, that number would reach 75 per cent by 2100. In 2015, the region experienced a deadly heat wave that killed roughly 3,500 people in Pakistan and India over a few months. “That was only the tip of the iceberg,” Eltahir said. “In the sense that much more severe heat waves are coming.” The study doesn’t directly address migration but researchers said it is likely that millions of South Asia will be forced to move due to blistering temperatures and crop failures unless steps are taken to reduce greenhouse gas emissions. People in the Middle East and parts of Africa have already started moving because of extreme heat and drought, Eltahir said. “Reducing our carbon emissions now will really make a difference in the future.”