A groundbreaking study from the Pennsylvania State College of Health and Human Development, in collaboration with Purdue University, has delivered a stark warning about the perilous impact of global warming on human health.
The study, published in the Proceedings of the National Academy of Sciences, indicates that a modest one-degree Celsius increase in global temperatures could subject billions of people to extreme heat, surpassing their natural ability to cool down.
The research, which models temperature increases ranging from 1.5°C to 4°C, highlights the alarming consequences if global temperatures exceed the 1.5°C target set by the Paris Agreement. At 2°C above pre-industrial levels, regions including Pakistan and India's Indus River Valley, eastern China, and sub-Saharan Africa are predicted to endure annual heat episodes surpassing human tolerance.
Co-author W Larry Kenney, a professor of physiology and kinesiology at Penn State, emphasises the necessity of interdisciplinary collaboration, stating, "To understand how complex, real-world problems like climate change will affect human health, you need expertise both about the planet and the human body."
The study establishes an ambient wet-bulb temperature limit of about 31°C, beyond which even young, healthy individuals would struggle with heat-related health issues. If global temperatures increase by 3°C, the Eastern Seaboard, the middle of the United States, South America, and Australia would also face extreme heat events beyond human tolerance.
Lead author Daniel Vecellio, a bioclimatologist, sheds light on the broader consequences, stating, "We will live in a world where crops are failing and millions or billions of people are trying to migrate because their native regions are uninhabitable."
Challenging traditional models, the study underscores the threat of humid heat over dry heat, urging governments and policymakers to reassess heat-mitigation strategies and invest in programmes to address the imminent dangers. Even regions with heatwaves below identified human limits raise concern, especially for vulnerable populations.
The researchers conducted 462 experiments to comprehend human limits in heat, humidity, and physical exertion. The empirical evidence builds on earlier research by Kenney's team, revealing that the body's ability to tolerate heat is lower than previously believed.
Beyond immediate health concerns, the study stresses the imperative need for global efforts to reduce greenhouse gas emissions, particularly carbon dioxide from burning fossil fuels. Failure to do so could disproportionately affect middle-income and low-income countries, with Yemen's Al Hudaydah cited as an example of a city potentially becoming almost uninhabitable if the planet warms by 4°C.
In an interconnected world, the study warns that everyone can expect negative consequences if drastic actions to combat climate change are not taken.