We didn't have temperature measuring stations in many countries (land-based measurements) along with sea surface temperature (70% of earth's surface) before the 1950s, but somehow climate scientists came up with a deviation from surface temperature anomaly from a "normal" anomaly of Earth's surface temperature.
In 1979 science figured out a way to measure surface temperature through satellites in order to verify surface temperature anomalies (enter James Hansen). Making science viable was important to atmospheric scientists when it comes to being accurate in measuring and theory. IMO this is where "rocket surface temperature science" was invented. Surface ocean temperature wasn't invented yet.
Ocean surface temperature was invented through ARGO data.
ARGO data gave climate scientists validation to propose even more Global Warming just like satellites gave alarmist scientists justification in documentation. There was absolutely no way to verify temperature data before satellites. They used BAD DATA to verify BAD DATA when satellites came.
Documenting Earth's overall surface temperature has only recently come to an idealized fruition with the advent of ARGO data, but we are far from understanding Earth's overall surface temperature.
Manipulating temperatures is easy. Proving that 1 part in 10,000 change in atmospheric physiology causes a 0.1C change is still based upon a theory.
We still can't accurately measure surface temperature.
Measuring surface temperature has changed too much when comparing realistic projections.
Climate science is still clueless about a great many things, especially temperature!