If current efforts to combat climate change remain unchanged, the Earth could experience a temperature increase of 2.7 degrees Celsius by the end of this century, according to a recent study conducted by researchers at the Global Systems Institute, University of Exeter, and Nanjing University.

This rise in temperature poses the greatest risk of extreme heat to India's population. The study reveals that assuming a future population of 9.5 billion, approximately 600 million people in India would be exposed to extreme heat.

However, the study also highlights that if global warming can be limited to 1.5 degrees Celsius, a significant portion of the global population—around one-sixth—could be spared from extreme heat compared to a 2.7-degree Celsius warming scenario.

But, what about the Paris Agreement?

One may question the effectiveness of the Paris Agreement in addressing this issue. The research suggests that despite the commitments made under the Paris Agreement to keep global warming below 2 degrees Celsius, current global policies indicate that temperatures are likely to rise to 2.7 degrees Celsius by the end of the century.

The Paris Agreement, which is a legally binding international treaty on climate change, was adopted by 196 parties during the UN COP21 in Paris in December 2015 and came into effect on November 4, 2016. Its primary objective is to limit the global average temperature increase to below 2 degrees Celsius above pre-industrial levels, with efforts made to restrict the rise to 1.5 degrees Celsius.

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However, in the past few years, world leaders have been looking at the importance of limiting global warming to 1.5 degrees Celsius by the century-end, after the UN's IPCC indicated that crossing the threshold risked unleashing more severe consequences of climate change, including more frequent heatwaves, rainfall and droughts.

"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," Tim Lenton, the director of Global Systems Institute, University of Exeter, said.

He added that for every 0.1 degrees Celsius of warming above the current levels, around 140 million people would be exposed to dangerous heat. "This reveals both the scale of the problem and the importance of decisive action to reduce carbon emissions," he said.

Other key findings of of the study

Exposure to extreme heat begins to rise dramatically at 1.2 degrees Celsius (just above present global warming) and increases by around 140 million for every 0.1 degrees Celsius of more warming.

Assuming a population of 9.5 billion people in the future, India will comprise the greatest population that will be exposed at 2.7 degrees Celsius warming, and this would be over 600 million people. At 1.5 million, this figurer, around 90 million.

Nigeria will have the second-largest population exposed to extreme heat at 2.7 degrees Celsius of the planet warming -- 300 million people. At 1.5 degrees Celsius warming, this will be less than 40 million.

India and Nigeria have already been showing 'hotspots' of dangerous temperatures.

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At 2.7 degrees Celsius, almost the entirety of some countries, including Mali and Burkina Faso, would be dangerously hot for human beings, the research stated. Brazil will have the largest land area that will be exposed to dangerous heat, even though there would be almost no area exposed at 1.5 degrees Celsius. The areas exposed to extreme heat will increase massively in India and Australia.

The human climate niche

Areas where human beings have been living because of favourable climate conditions are called the human climate niche. The study states that historically, human population density has peaked at all places than have an average temperature of around 13 degrees Celsius, and a secondary peak of around 27 degrees Celsius (in monsoon climates, especially in southern Asia).

The report stated that the density of livestock and crops follow similar patterns and economic growth (wealth or GDP) also peaks at 13 degrees Celsius. It also stated that mortality also increases at both, higher and lower temperatures, hence supporting the idea of a human "niche".

It added that at present less than 1 percent of our species live in places of extreme heat exposure and climate change has already put 9 percent of the entire global population (over 600 million people) outside the niche.

"Most of these people lived near the cooler 13°C peak of the niche and are now in the ‘middle ground’ between the two peaks. While not dangerously hot, these conditions tend to be much drier and have not historically supported dense human populations," Chi Xu, a professor at Nanjing University, said.

Xu added that while a vast majority of people are set to be left out of the niche because of future warming and would be exposed to dangerous heat. "Such high temperatures have been linked to issues including increased mortality, decreased labour productivity, decreased cognitive performance, impaired learning, adverse pregnancy outcomes, decreased crop yield, increased conflict and infectious disease spread," Xu said.

Some cooler places could become more habitable because of climate change, however the population growth is estimated to be the highest in places that are at risk of dangerous heat, especially Nigeria and India, the report stated.

What does the research suggest?

The research team stressed that the worst of these impacts could be avoided if rapid action is taken to cut greenhouse gas emissions.

"We are already seeing effects of dangerous heat levels on people in different parts of the world today. This will only accelerate unless we take immediate and decisive action to reduce greenhouse gas emissions," said Wendy Broadgate, Executive Director of the Earth Commission at Future Earth.

Ashish Ghadiali of Exeter’s Global Systems Institute said that these new findings underline the profoundly racialised nature of projected climate impacts and should inspire a policy sea-change in thinking around the urgency of decarbonisation efforts and in the value of massively up-shifting global investments into the frontlines of climate vulnerability.

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