A recent study conducted by Penn State University has unveiled alarming heat maps that depict a future where several countries may become inhospitable due to rising global temperatures. Even a modest increase of 1.5°C (2.7°F) could render regions across the world too hot for human habitation. It’s a wake-up call to the world, urging immediate action to combat climate change and adapt to the impending heat-related challenges.
The study paints a grim picture, highlighting the vulnerability of vast populations in various parts of the world. Approximately 2.2 billion people residing in Pakistan and India’s Indus River Valley, another billion in eastern China, and 800 million in sub-Saharan Africa could face heat levels that surpass human endurance. Furthermore, if global temperatures rise by 3°C (5.4°F) above pre-industrial levels, even regions in the eastern and central United States, including Florida, New York, Houston, and Chicago, could suffer from stifling humidity and extreme heat.
The “wet-bulb temperature” (TW), a measure in both temperature and humidity, is a crucial indicator of heat-related risks. When TW exceeds 103°F, the human body loses its ability to cool down effectively, reaching a state deemed “dangerous” by the US National Weather Service. Beyond 124°F, extreme danger looms, leading to heat stroke and potential damage to vital organs.
The elderly, children, and individuals with health issues face higher risks, but as global temperatures continue to rise, billions more could be in jeopardy. At certain heat and humidity levels, the body’s natural cooling mechanisms fail, leading to conditions like heat exhaustion, heat stroke, and cardiovascular strain.
Recent heatwaves in the US, Europe, and China underscore the pressing issue of heat-related threats. Previous estimates had set the upper limit for human safety at a wet-bulb temperature of 95°F (35°C), but the latest research reveals it to be much lower at 87°F (31°C) under specific humidity conditions.
The study emphasizes that it’s not just the temperature on the thermometer that matters; the combination of heat and humidity, or the “wet-bulb temperature,” determines the risk. Historically, instances of temperatures and humidity exceeding human limits have been rare and short-lived, primarily occurring in the Middle East and Southeast Asia.
Since the industrial revolution began, global temperatures have already risen by approximately 1°C (1.8°F). The Paris Agreement, signed by 196 nations in 2015, aims to limit global temperature increases to 1.5°C (2.7°F) above pre-industrial levels. However, the study models scenarios where temperatures could rise by up to 4°C (7.2°F), which would have devastating consequences for regions in India, Pakistan, China, and sub-Saharan Africa.
What’s particularly concerning is that many of the most affected areas are in lower-to-middle income nations with limited access to air conditioning, making them highly vulnerable to heatwaves. In the worst-case scenario, cities like Al Hudaydah in Yemen could become nearly uninhabitable, with temperatures surpassing human tolerance on most days.
The study underscores the urgency of addressing climate change and implementing effective heat-mitigation strategies. Governments and policymakers need to prioritize humidity-related heat risks and invest in programs to safeguard vulnerable populations.
Regardless of the extent of warming, people must remain vigilant about extreme heat, particularly when it endangers the elderly and those with health issues. Heat has already proven to be a deadly weather phenomenon, and proactive measures are essential.
This groundbreaking study has been published in the Proceedings of the National Academy of Sciences journal.