Scientists warn dangerous levels of heat will threaten two billion people

Some countries will be left uninhabitable, while India will have largest population exposed to extreme heat

Climate inaction could expose more than two billion people to dangerous heat conditions, with the whole of some countries becoming too hot for humans to live in, a new study warns.

About 22 per cent of the world’s projected end-of-century population will be affected, said the research conducted by scientists from the Global Systems Institute at the University of Exeter and Nanjing University that was released on Monday.

It emphasised how the narrow “climate niche”, the specific climatic conditions that have historically supported human habitation, is rapidly shrinking due to global heating, particularly affecting areas with lesser carbon emissions.

One sixth of humanity – approximately a billion people – could be saved from the impacts of dangerous heat if countries somehow manage to keep global heating to 1.5C, the ideal goal of the Paris Agreement, the study says.

In 2015, almost 200 countries signed the Paris Agreement agreeing to make efforts to control the global temperature rise to 1.5C, or a maximum 2C, above preindustrial levels.

The window to be able to limit warming to that level is shrinking rapidly, according to various scientific assessments. A new report from the World Meteorological Organisation warns the world is expected to hit the 1.5C threshold within the next five years.

Current policies are projected to result in a 2.7C temperature increase by the end of the century.

While about 9 per cent of humanity – 60 million people – is already exposed to extreme heat as the world has warmed up to 1.2C due to human-induced greenhouse gas emissions, a 2.7C rise would leave more than two billion people vulnerable to a dangerously hot climate.

With every 0.1C of warming above present levels, an additional 140 million people will be exposed to hazardous heat conditions, the research indicates.

The costs of global warming are often expressed in financial terms, but our study highlights the phenomenal human cost of failing to tackle the climate emergency.

Professor Tim Lenton, director of the Global Systems Institute

“Limiting global warming to 1.5C rather than 2.7C would mean five times fewer people in 2100 being exposed to dangerous heat,” says professor Tim Lenton, director of the Global Systems Institute.

The research also reveals the inequity of the climate crisis: the lifetime emissions of 3.5 average global citizens or 1.2 US citizens expose one person in the future to dangerous heat.

These future heat-exposed individuals reside in regions where current emissions are only half the global average.

Areas with higher population growth, particularly in India and Nigeria, are projected to be the most at risk of dangerous heat.

India, which is already experiencing deadly heatwaves, has the largest population that will be at risk, with 600 million people exposed to extreme heat if temperatures rise by 2.7C.

At 1.5C, this figure would be about 90 million.

Also read: Awards ceremony turns to tragedy in India as 11 die and hundreds hospitalised with heatstroke

Nigeria would have more than 300 million people at risk at 2.7C heating. But with 1.5C, this would be less than 40 million.

At 2.7C, almost 100 per cent of some countries, including Burkina Faso and Mali, will be dangerously hot for humans.

Brazil would have the largest land area exposed to dangerous heat, despite almost no area being exposed at 1.5C, while Australia will witness significant increases in exposed areas.

“The costs of global warming are often expressed in financial terms, but our study highlights the phenomenal human cost of failing to tackle the climate emergency,” Mr Lenton says.

Homeless people sleep in the shade of an overpass to beat a heat wave in New Delhi (AP)

“We were triggered by the fact that the economic costs of carbon emissions hardly reflect the impact on human wellbeing,” says professor Marten Scheffer, of Wageningen University, one of the authors of the report.

“Our calculations now help bridging this gap and should stimulate asking new, unorthodox questions about justice.”

In the worst-case scenarios of 3.6C or 4.4C global heating, the study warns that half of the world’s population could be left exposed to dangerous conditions, posing an existential risk.

The impacts of extreme heat include increased mortality, decreased labour productivity, impaired learning, adverse pregnancy outcomes, decreased crop yield, increased conflict and the spread of infectious diseases.

While some cooler regions are set to become warmer, the overall impact on the planet of this level of global heating would be disastrous for every region, several reports from the Intergovernmental Panel on Climate Change (IPCC), the UN’s top scientific panel, have repeatedly warned.

Global heating is already leading to melting glaciers, sea level rise, shrinking freshwater lakes and more frequent extreme weather events.

Also read: One in three people on the planet hit by ‘monster Asian heatwave’

“We are already seeing effects of dangerous heat levels on people in different parts of the world today,” says Wendy Broadgate, executive director of the Earth Commission at Future Earth.

“This will only accelerate unless we take immediate and decisive action to reduce greenhouse gas emissions.”

The research team, including scientists from various institutions, stressed the need for rapid action to reduce greenhouse gas emissions to avoid the worst impacts.

“These new findings from the leading edge of Earth systems science underline the profoundly racialised nature of projected climate impacts,” says Ashish Ghadiali of the Global Systems Institute.

He adds that the findings should “inspire a policy sea-change in thinking around the urgency of decarbonisation efforts as well as in the value of massively up-shifting global investment into the frontlines of climate vulnerability”.