A BILLION people could be living with potentially lethal levels of heat stress if global warming were to reach 2C, research has found.

Heat stress - a dangerous mix of heat and humidity above 32C - already affects 68m people globally.

It can lead to heat exhaustion, with symptoms including heavy sweating and a rapid pulse, straining the heart and other organs.

The elderly, those with pre-existing health conditions and those with physical, outdoor jobs are at the greatest risk.

Before COP26, the earth was on course for 2.7C of warming above pre-industrial levels, but recent pledges to cut carbon emissions have lowered that trajectory to 1.8c.

New modelling from academics and the Met Office suggests that under a 2C scenario, the number of people living in heat stress conditions could rise 15-fold.

If runaway global warming hit 4C, half of the world’s population would be living with heat stress.

The findings are from an international team of scientists in the EU-funded Helix project, and led by the University of Exeter

The Met Office analysed where the worst impacts overlapped on behalf of the UK Government.

The heat stress maps also look at river flooding, wildfire risk, drought and food insecurity.

Dr Andy Wiltshire, head earth system and mitigation science at the Met Office, said: “Parts of the tropics are most affected with countries like Brazil and Ethiopia potentially facing impacts from four of the hazards.

“Rapid emission reductions are required if we are to avoid worst consequences of unmitigated climate change.

Prof Richard Betts, of the University of Exeter and Met Office, who led the Helix project, said “This new combined analysis shows the urgency of limiting global warming to well below 2C.

“The higher the level of warming, the more severe and widespread the risks to people’s lives, but it is still possible to avoid these higher risks if we act now.”

Dr Andy Hartley, climate impacts lead at the Met Office, said: “Our analysis shows that with a rise of 4C, extreme heat risk could affect people in large swathes of most of the world’s continents.”