The research, conducted by scientists from the Global Systems Institute at the University of Exeter in collaboration with the Earth Commission and Nanjing University, reveals that approximately 60 million people already experience average temperatures of 29°C or higher, which are classified as dangerous heat. If global warming reaches 2.7°C, an estimated two billion individuals, or 22% of the projected end-of-century population, would be exposed to these hazardous conditions.
Professor Tim Lenton, Director of the Global Systems Institute at the University of Exeter, emphasized the profound human cost of failing to address the climate emergency, stating, “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.”
The study, published in the journal Nature Sustainability, underscores the significant potential of decisive climate policies in mitigating the human toll of climate change. It suggests that rapid action to reduce greenhouse gas emissions can prevent the majority of the projected damage. Prof. Lenton noted that limiting global warming to 1.5°C instead of 2.7°C would result in five times fewer people being exposed to dangerous heat by 2100.
The research introduces the concept of a human “niche” and highlights that human population density typically peaks in areas with an average temperature of around 13°C, with a secondary peak at approximately 27°C, particularly in South Asia. While less than 1% of the global population currently resides in locations with dangerous heat exposure, the study reveals that climate change has already pushed 9% of the global population, or over 600 million people, beyond their optimal niche. These individuals now find themselves in the “middle ground” between the two temperature peaks, which, although not dangerously hot, tend to be drier and historically unable to support dense human populations.
Furthermore, the study indicates that while some cooler regions may become more habitable due to climate change, the highest population growth is projected to occur in areas at risk of dangerous heat, particularly in India and Nigeria. Assuming a future global population of 9.5 billion people, India would face the highest population exposure to dangerous heat at 2.7°C global warming, affecting over 600 million individuals. However, at 1.5°C warming, this figure would be significantly lower, around 90 million.
Professor Marten Scheffer of Wageningen University emphasized that the economic costs of carbon emissions do not adequately reflect their impact on human well-being. He called for new and unconventional approaches to questions of justice in addressing the climate crisis. The study also highlights that countries such as Burkina Faso and Mali would become predominantly exposed to dangerously hot conditions with a 2.7°C temperature increase, while Brazil would have the largest land area exposed to dangerous heat.
The findings of this study underscore the urgent need for enhanced climate action to limit global warming and protect vulnerable populations from the escalating risks of dangerous heat.
