Current climate policies are on track to expose over a fifth of the global population to dangerously hot temperatures by 2100, risking human lives and well-being, according to a new study by researchers at the Global Systems Institute, University of Exeter.
Despite the Paris Agreement's commitment to keeping global warming below 2°C, the study projects a 2.7°C increase by the end of the century.
This temperature rise would mean 2 billion people, approximately 22% of the future population, would endure hazardous heat conditions. In contrast, limiting warming to 1.5°C would significantly reduce the number of people affected, sparing a sixth of humanity from dangerous heat.
The research emphasises the pressing need for immediate climate action to curb the human costs and inequalities associated with climate change.
About 60 million people live in areas with temperatures averaging 29°C or higher, classified as dangerous heat. Tragically, if global warming reaches 2.7°C, this number will skyrocket to 2 billion individuals. However, reducing warming to 1.5°C would result in only 5% of the population being exposed to such hazardous conditions.
The study sheds light on the inequities of the climate crisis, as the lifetime emissions of just 3.5 global citizens or 1.2 US citizens are responsible for exposing 1% in the future to dangerous heat. In worst-case scenarios of 3.6°C or 4.4°C global warming, half of the world's population could find themselves outside the "climate niche," posing an existential risk.
Professor Tim Lenton, the director of the Global Systems Institute at the University of Exeter, underscores the staggering human toll of inaction, stating that every 0.1°C of warming above current levels would expose an additional 140 million people to dangerous heat. The study highlights the urgency of addressing carbon emissions and reducing global warming to 1.5°C instead of 2.7°C.
Defining the human "climate niche" based on historical population density and temperature patterns, the study reveals that less than 1% of the global population currently resides in areas with dangerous heat exposure. However, climate change has already forced 9% of the worldwide population, exceeding 600 million people, outside this niche. Most of these individuals previously lived in regions near the cooler 13°C peak and now find themselves in a transitional zone between the two temperature peaks.
The consequences of dangerous heat are far-reaching, including increased mortality, decreased labour productivity, impaired learning and cognitive performance, adverse pregnancy outcomes, reduced crop yields, heightened conflict, and spreading infectious diseases. Although some cooler regions may become more habitable due to climate change, population growth is projected to be highest in areas vulnerable to dangerous heat, particularly in India and Nigeria.
The study also reveals that exposure to dangerous heat intensifies dramatically at 1.2°C of warming, increasing by approximately 140 million people for every 0.1°C rise after that. India would be most affected by 2.7°C global warming, with over 600 million people exposed, compared to around 90 million at 1.5°C warming. Nigeria would have the second-largest population exposed at 2.7°C, exceeding 300 million, decreasing to less than 40 million at 1.5°C warming.