The Time of Observation Bias (TOB) adjustment is the primary excuse for rewriting US temperature history.
I have new tools in place which show what a farce that is. The graph below plots the summer 1936 average daily maximum temperature of all Missouri stations which took their readings during morning/night in blue, and all stations which took their readings during afternoon/evening in red. The yellow line is the average for all Missouri stations this summer. The reason I used Missouri is that they have an excellent temperature record, the state is small, and had a nearly even mix of morning and afternoon stations during 1936.
As you can see, there is very little difference between the morning and afternoon stations from 1936, but there is a huge difference between 1936 and 2019. This summer has been thirteen degrees cooler than 1936.
The afternoon stations in the graph above average about 0.7F warmer than the morning stations. Let’s look at what is causing this. The trend since 1895 is nearly identical for both groups, with the set of afternoon stations consistently warmer by about 0.7F until the most recent decade.
The cause of this is that the afternoon stations in 1936 averaged about half a degree of latitude (35 miles) further south, which corresponds to about 0.9F warmer temperatures.
The entire (tiny) difference between morning and afternoon stations can be completely accounted for by differences in latitude. There is no indication TOB has any impact on measured temperatures. TOB is just one more lame excuse to erase America’s hot past.
Station information was taken from here. NOAA is making it harder and harder to find this information, so I had to pull it off the web archive.
1936 Morning Stations USC00232809.dly : FARMINGTON MO 37.7922 -90.4103 USC00234271.dly : JEFFERSON CITY WTP MO 38.5853 -92.1825 USC00234705.dly : LAMAR 7N MO 37.5983 -94.2842 USC00234825.dly : LEBANON 2W MO 37.685 -92.6939 USC00234850.dly : LEES SUMMIT REED WR MO 38.8803 -94.3358 USC00234904.dly : LEXINGTON 3E MO 39.1828 -93.855 USC00235541.dly : MEXICO MO 39.1756 -91.8861 USC00235671.dly : MOBERLY MO 39.4194 -92.4369 USC00235834.dly : MTN GROVE 2 N MO 37.1542 -92.2619 USC00238523.dly : UNIONVILLE MO 40.475 -93.0031 1936 Afternoon Stations USC00230204.dly : APPLETON CITY MO 38.1872 -94.0283 USC00230856.dly : BOWLING GREEN 1 E MO 39.3444 -91.1711 USC00231037.dly : BRUNSWICK MO 39.4247 -93.1331 USC00231364.dly : CARUTHERSVILLE MO 36.1875 -89.66 USC00231711.dly : CLINTON MO 38.395 -93.7711 USC00231822.dly : CONCEPTION MO 40.2394 -94.6833 USC00232289.dly : DONIPHAN MO 36.6206 -90.8125 USC00235027.dly : LOCKWOOD MO 37.3908 -93.9492 USC00235253.dly : MARBLE HILL MO 37.3036 -89.9664 USC00235976.dly : NEOSHO MO 36.865 -94.3603 USC00237263.dly : ROLLA MISSOURI S&T MO 37.9567 -91.7761 USC00237963.dly : SPICKARD 7 W MO 40.2472 -93.7158 USC00238051.dly : STEFFENVILLE MO 39.97 -91.8875 USC00238223.dly : SWEET SPRINGS MO 38.9664 -93.4194 USC00238466.dly : TRUMAN DAM & RSVR MO 38.2597 -93.4136 USC00238725.dly : WARRENTON 1 N MO 38.835 -91.1386
If TOB doesn’t work in Missouri, it isn’t going to work anywhere.