Humanity has missed its chance of keeping global warming below 1.5C and it will take “heroic efforts” to stay below 2C this century, the scientist leading the global effort to understand climate change has warned.

Jim Skea, chairman of the Intergovernmental Panel on Climate Change (IPCC), said a failure to sufficiently curb carbon emissions had left the world on track to warm by 3C by 2100. This average masks variations between land and sea, with western Europe and the UK facing even greater warming – perhaps as much as 5C by the end of the century.

“We are potentially headed towards 3C of global warming by 2100, if we carry on with the policies we have at the moment,” said Skea.

“Obviously temperature rises over land will be higher than over the ocean. We don’t know how warm it will get [over land] but I know it may be more than the global average.”

The Met Office has tried to project the UK impacts. By 2070, it says, winters will be up to 4.5C warmer but 30pc wetter, meaning more flooding. Summer will be up to 6C warmer, with frequent droughts and surging numbers of heat-related deaths...