Heat stress — a potentially fatal mix of warmth and humidity — will afflict fifteen times more people should global temperature rise exceed the 3.6°F (2°C) threshold.
Heat stress affects approximately 68 million people around the world at present. However, this number would shift to one billion or one in eight people.
A 7.2°F (4°C) overall increase, meanwhile, would see half of the world’s population living in areas that are at risk, a study from the UK Met Office has today warned.
The findings come in a series of maps that explore which regions would be affected by five different climate effects under both 3.6°F (2°C) and 7.2°F (4°C) of warming.
These maps were created using data from an international team, led by University of Exeter.
Met Office analyses specifically where more severe effects might overlap and which areas are most susceptible to food insecurity.
The experts found that areas in the tropics will be the worst affected — with impacts from four or more of the hazards striking in countries like Brazil and Ethiopia.
A 7.2°F (4°C) overall increase in global temperatures would see half of the world’s population living in areas that are at risk of heat stress, a study from the UK Met Office has today warned. Pictured: a map of the world under 7.2°F (4°C) of global warming showing those areas where people are at extreme risk of heat stress for more than 10 days in the year
‘This new combined analysis shows the urgency of limiting global warming to well below 2.0°C [3.6°F]Richard Betts, a Met Office climate scientist and project leader at the University of Exeter, said:
‘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.’
Humans are considered at ‘extreme risk’ of heat stress when the so-called wet bulb globe temperature — which takes into account temperature, humidity, cloud cover, sun angle and wind speed — exceeds 89.6°F (32°C).
Andy Hartley, Met Office, stated that hourly rest is recommended in order to prevent heat exhaustion above this level. He also said that ‘vulnerable individuals’ and people who have physical outside jobs are at higher risk for adverse effects.
He added that the current metric was met at several places, including 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.’
Met Office analysis focuses on areas where more severe effects might be combined and vulnerable to food insecurity. Pictured: this map of the world under 7.2°F (4°C) of warming shows where severe impacts from drought, heat stress, river flooding and wildfire risk overlap with each other and areas of food insecurity today
‘Any one of the climate impacts presents a scary vision of the future,’ said the Met Office’s head of earth system and mitigation science, Andy Wiltshire.
“But, obviously, severe climate change is going to have many effects, and our maps indicate that certain regions could be affected by several 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 emissions reductions are needed if we wish to avoid the most severe consequences of unmitigated global warming.”
‘These maps reveal areas of the world where the gravest impacts are projected to occur with higher levels of global warming,’ said Met Office Hadley Centre director Albert Klein Tank.
‘However, all regions of the world — including the UK and Europe — are expected to suffer continued impacts from climate change,’ he warned.
Next year, the Intergovernmental Panel on Climate Change will be publishing its Working Group II Impacts, Adaptation and Vulnerability report, including an assessment of the vulnerability of socio-economic systems to climate change.