In the summer of 2023, a dozen people willingly walked into a steel chamber at the University of Ottawa designed to test the limits of human survival. Outfitted with heart rate monitors and temperature probes, they waited in temperatures of 42 degrees Celsius, or 107 degrees Fahrenheit, while the humidity steadily climbed, coating their bodies in sweat and condensation. After several hours, their internal body temperatures began ratcheting upward, as the heat cooked them from the outside in.
“Few people on the planet have actually experienced temperatures like this,” said Robert Meade, a postdoctoral researcher in epidemiology at the Harvard School of Public Health who led the study. “Imagine moisture condensing on the skin like a glass of water on a hot day. That’s how hot it was, compared to skin temperature.”
Their experiment tested the body’s ability to cope with extreme heat by exposing participants to temperatures at which they could no longer cool themselves. Their study confirmed that this dangerous threshold is much lower than scientists had previously thought: a so-called wet-bulb temperature, which accounts for heat and humidity, of 26 to 31 degrees C.
https://archive.ph/Lj16Y
EDIT: I finally found the answer. The article is talking about 31°C wet bulb temperatures, which is equivalent to 100% rH.
At 100% rH, 31°C is a heat index temperature of 49°C (120°F or 322k).
So if it hits 49°C at ~33%rH you might want to turn up the aircon a notch.
~~So 31c at checks notes 92% rH? Wow I sure am worried now!~~
~~Even in the eternally damp UK rn the rH is 31% and at that level it'd need to be 41c before it causes any problems at all~~
~~This tracks with my personal experience where 30-35c feels pretty warm but not too warm for a nice summer day. Past 35c I'd avoid public transport and maybe wear white and would probably keep a fan going indoors occasionally~~
~~Am I wrong? Please dunk on me if I just don't get it, because otherwise I feel like this article is kind of misleading~~
As someone having tried 48-49°C and somewhere around 20-30% I would not recommend. I sure prefer -35°C. I mean if I have to choose.
The article is not misleading, it's simply stating/confirming the known facts (the temperature at which vital proteins in our bodies start to degrade is very well known, feaver is the name).
Your assumption is that you may never face extreme conditions which may be right - climate change in its core is a chaotic process. That still doesn't mean that conditions won't rise to levels where younger and older and weaker persons - who have a much smaller frame of acceptance for higher physiological stress levels - aren't affected. The people in the test were young and healthy - well, guess what, that's not everyone.
So you are right but you don't account for or care for significant numbers of your countrymen. That's ok but it narrows the broader picture we need to look at as a civilisation.
I'm trying to understand what exactly those conditions are more than anything. The articles frames the findings as temperatures of 31c breaking down important proteins in the human body to ill effect, but this cannot be true because there are many regions in the world where temperatures stay up even higher for prolonged periods of time and yet the people that inhabit them are completely fine.
We also know that humidity levels in a given temperature actually impact significantly how we experience it and what the health risks are, due to our bodies' evaporative cooling.
What I don't seem to see in the article are specifics, what is the rH % at which 31c has such a negative effect? What rH % is a "wet bulb" temperature equivalent? In human terms, what temperature per rH % did these experiments find to be harmful? Because as I described, 31c at 33% rH does not even feel that warm, nevermind harmfully hot.
I have tried googling this as well but I think I'm just not phrasing it correctly or the question I'm asking is so stupid and obvious that there's no actual written answer.
Here's a book that dives very deep into the topic:
https://en.m.wikipedia.org/wiki/The_Heat_Will_Kill_You_First
If you don't like to buy the book just read and watch the numerous articles and videos about this book and its author.
This seems more like a narrative about the climate crisis and heat deaths. Tragic as they are, it doesn't seem like it would answer my question.
If you want to quote a passage from the book that explains whether anything has changed with the OP article in terms of lethality and/or harm of certain levels rH% and °C then I'd be happy to take a look.
I haven't run the numbers, but your assessment seems about right. The lower the humidity, the greater the potential for evaporative cooling, and the higher the max tolerable temperature. No reason to avoid moving to the tropics anytime soon.