Extreme heat could prove to be potentially fatal for up to one billion people if the world’s temperature rise reaches 2°C says the UK’s Met Office.

The research, which has been released at the Cop26 climate summit this week said that the number of people exposed to risk by the two degree rise will increase by up to 15 times. There are already 68m people under threat, the same report suggests that if temperatures rose by 4°C then half the planet’s population could be affected.

The Met Office have used a recognised temperature of 32°C as an indicator, with anyone working above these levels likely to require increased rest time to avoid heat exhaustion.

“Above this level people are defined as being at extreme risk,” said Dr Andy Hartley, Climate Impacts Lead at the Met Office. “Vulnerable members of the population and those with physical outdoor jobs are at greater risk of adverse health effects.

Currently, the metric is met in several locations, such as parts of India, but our analysis shows that with a rise of 4.0°C, extreme heat risk could affect people in large swathes of most of the world’s continents.”

As well as heat, the research also revealed what other extreme weather factors would be influenced by the rise in temperatures, with a map demonstrating which areas of the planet would be impacted by river flooding, risk of wildfire, drought and food insecurity.

Dr Andy Wiltshire, Head Earth System and Mitigation Science, added: “Any one of the climate impacts presents a scary vision of the future. But, of course, severe climate change will drive many impacts, and our maps show that some regions will be affected by multiple factors.

“Perhaps unsurprisingly, 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.”