The Spark, MIT Technology Review’s climate newsletter, delves into the effects of extreme heat on the human body and how climate change is testing our physiological limits. It details the complex factors that determine how much heat the human body can withstand, such as age, health status, and humidity. The theoretical limit of the human body is typically measured at 95 °F (35 °C) on a wet-bulb temperature scale, though recent research indicates this limit might vary. The article also covers how our bodies can adapt to heat, but emphasizes that such adaptation will not be enough to protect against climate change-induced heat, necessitating reliance on cooling technologies and recognizing heat as an equity issue.
  

Key Points: 

1. Understanding Human Heat Tolerance: The human body needs to maintain a core temperature of around 98.6 °F (37 °C), but extreme heat can derail this balance, leading to health issues. Factors like age, health status, and acclimatization to heat determine how much heat the body can lose.
2. Wet-Bulb Temperature Metric: Wet-bulb temperature is a metric that considers both heat and humidity to gauge how much sweat can cool you down. Typically, the theoretical limit for human tolerance is 95 °F (35 °C) on this scale, but new research suggests it might be lower, especially in humid conditions.
3. Body’s Ability to Adapt to Heat: The body can acclimatize to heat, adjusting in ways such as increasing plasma volume and changing the sweating process. However, this adaptation is limited and won’t be enough to keep people safe in extreme heat, particularly if they work in hot conditions.
4. Heat as an Equity Issue: The article emphasizes the need for cooling devices like air conditioners and fans, along with other measures, to stay safe in increasing temperatures. This underlines the equity issue, as not everyone has access to reliable cooling technology or the ability to shelter inside.
5. The Interplay of Climate Change and Human Health: The article connects the discussion of human heat tolerance to the broader context of climate change, emphasizing that understanding our physiological limits is part of a complex, multifaceted response to a warming planet. Efforts to adapt must also include technology, infrastructure, and awareness of social and economic disparities.

Source: https://www.technologyreview.com/2023/08/03/1077155/extreme-heat-health