> During their simulation of Mallory’s Everest expedition, the data showed that on summit night, the average body temperature difference between the twin in modern down and the twin in complicated layers of silk, wool, and gabardine was a staggering 1.8°C.

The human body self-regulates, and is pretty sensitive to dramatic temperature swings. So, conditioned on the fact that they both survived the adventure, we should expect their temperature differences to be relatively small. This doesn't mean the clothing is great, it means [their body] + [their clothing] is adequate.

Additionally, I'm not a doctor but 1.8 C is not small compared to normal human variation! Normal body temperature ranges between 36 and 37 C, a "high fever" starts around 39 C [0], and hypothermia is anything below 35 C [1]. The comfortable range of human temperature is 1 deg C, and the "outside of this is concerning" range is only 4 C wide. 1.8 C is quite big from that perspective.

[0] https://www.health.harvard.edu/diseases-and-conditions/treat...

[1] https://www.mayoclinic.org/diseases-conditions/hypothermia/s...

Right, the 1.8C difference is substantial in terms of human physiology and indicates a diminished level of comfort as the body fights to keep the temperature up.

I also found it funny how they mentioned that modern clothing keeps you warmer longer once you stop moving, then tried to minimize the significance of that. There's a reason "cotton kills" is a cliche. Modern fabrics, windbreaker shells, and engineered layers don't make a huge difference in warm, dry, active conditions - it's when things go sideways that they can be the difference between comfort and fatal hypothermia.

I didn't see more details in the article, but my guess is they were taking and averaging multiple temperature reads across the body. That is, core temp should only be within a narrow range like you say, but fingertip temp will vary much more widely.

All in all I found this to be a very strange article. If you just look at the data, I think a reasonable conclusion is that modern gear is vastly better at its function than old time Mallory gear. It's much lighter and keeps the wearer much warmer than old gear. But the whole tone of the article is about "myth busting" and how there haven't been really that many improvements in gear. I'm just looking at their charts and data and wondering what they're smoking.

It was 1.8 C difference in skin temperature, not core body temperature. As you note, 1.8 C would be massive for core temp.

Wearable thermometer patches attached to each man’s head, chest, hands, feet, and legs recorded body temperature at five-minute intervals, nonstop, for the entire 10 days of the expedition.

"Normal body temperature", ok but these are two mountaineering nerds (not normal) so who knows.

Not to be a stickler (ok I like being a stickler) but temperature delta, especially deltas between degrees celsius, should be given in kelvin. A 1.8K difference makes sense. A 1.8C difference would be 274.8 kelvin!