By comparison the hottest verified recorded air temperature in the world is 54°C

> if the current record were to be decertified then the holder would be a tie at 54.0 °C (129.2 °F), recorded both at Furnace Creek and in Kuwait.

https://en.wikipedia.org/wiki/Highest_temperature_recorded_o...

Open air. These days the interior of my car regularly exceeds 54 even with the windows cracked and a winshield shade up.

Soon to be average temperatures, what luck!

Nonsense.

It's obviously a hyperbole. But if we once were to use these SCs to transport energy from solar farms in Sahara, it might have to operate in that temperature range.

Five meters down in the desert you're under 25 degrees year round. It's the average that matters for soil temps, not the peaks. You can approximate this by taking the average air temperature and defining the surface as the top five meters. Below the 10 meter mark the day/night cycle influence is pretty much negligible (but that would be more costly).

For instance:

https://www.researchgate.net/figure/Temperature-variation-of...

Earth's average temperature right now is ~17° Celsius.

So...no.

Have you included the insides?