I was trying to find the mentioned paper by G. Hoffmann, but it's nowhere to be found. The ONLY source I can find searching for the title is the exact same paper. How disappointing!
However, I found the cited paper "Grenzwerte der Klimaelemente auf der Erde" by G. Hellmann which can be found here
. Hellmann talks about the highest temperature on earth being recorded in Death Valley and cites it as 56.6°C. Apparently it happened during a 7 days lasting heat wave, with maximum temperatures as follows:
07/08/13 -> 53.3
07/09/13 -> 53.807/10/13 -> 56.6
07/11/13 -> 53.8
07/12/13 -> 54.4
07/13/13 -> 54.8
07/14/13 -> 52.7
But at the same time the paper states that it is quite difficult to measure extreme temperatures. Extrem high temperatures, because it's difficult to exclude every other aspect like the ground reflecting the heat, wind, etc. and extrem low temperatures, because mercury freezes at ~ -38°C.
So, yeah... the Army Corps of Engineers isn't pulling a fast one, it seems.