NOAA makes a large adjustment to the US temperature record based on Time Of Observation Bias. The idea is that most station operators were morons in the 1930’s, and reset their min/max thermometers in the afternoon – causing double counting of warm days.
It is easy to test this, by eliminating all stations which took readings in the afternoon during July 1936.
The set of all stations shows about 0.3C warming since 1895.
The set of stations which took morning readings during July, 1936 shows slightly more warming – about 0.4C. These stations are biased cold in the past, because they took their readings too close to the daily minimum.
The total bias caused by afternoon TOBS is a little more than 0.1C (0.2F)
This is much less than the bloated adjustment used by USHCN. But what about hot days? Did afternoon TOBS cause double counting of hot days in 1936? The evidence shows that there was little if any such effect. The trend is almost identical between the two data sets.
The total NOAA adjustment is nearly two degrees F. It is unsupportable nonsense, and fraud.