The graph below organizes US HCN stations into two groups. Those that took morning readings (i.e. reset the thermometer in the morning or night) on July 15, 1936 and those which took afternoon readings (reset in the afternoon) on that date.
Both groups show identical downward trends in US maximum summer temperatures since 1910. If TOBS were real, the 1936 morning reset temperatures would be warming much faster than the 1936 afternoon reset temperatures. In actuality, the morning temperatures are cooling slightly faster than the afternoon temperatures.
This shows that TOBS has little or no effect on the temperature, and is simply another excuse to cool the past and turn a long term cooling trend into a warming trend.