Report says percentage of the world facing at least one day of extreme heat stress each year has risen from 16 per cent to 22 per cent since the 1970s, equivalent to around one billion additional people Sign up to the Independent Climate email for the latest advice on saving the planet Get our free Climate email Get our free Climate email Email * SIGN UP I would like to be emailed about offers, events and updates from The Independent. Read our Privacy notice A billion more people are now