The deadliest place on the planet for extreme future heatwaves will be the north China plain, one of the most densely populated regions in the world and the most important food-producing area in the huge nation.rnrnNew scientific research shows that humid heatwaves that kill even healthy people within hours will strike the area repeatedly towards the end of the century thanks to climate change, unless there are heavy cuts in carbon emissions.rnrn"This spot is going to be the hottest spot for deadly heatwaves in the future," said Prof Elfatih Eltahir, at the Massachusetts Institute of Technology, US, who led the new study. The projections for China's northern plain are particularly worrying because many of the region's 400 million people are farmers and have little alternative to working outside.rnClimate change to cause humid heatwaves that will kill even healthy peoplernRead morernrn"China is currently the largest contributor to the emissions of greenhouse gases, with potentially serious implications to its own population," he said. "Continuation of current global emissions may limit the habitability of the most populous region of the most populous country on Earth."rnrnThe new analysis assesses the impact of climate change on the deadly combination of heat and humidity, which is measured as the "wet bulb" temperature (WBT). Once the WBT reaches 35C, the air is so hot and humid that the human body cannot cool itself by sweating and even fit people sitting in the shade die within six hours.rnrnA WBT above 31C is classed by the US National Weather Service as "extreme danger", with its warning stating: "If you don't take precautions immediately, you may become seriously ill or even die."