Do we have sea temperature data from before 1982? Like, thousands of years'?
"The true heavyweights for reconstructing ancient seawater temperatures are the microorganisms. Foraminifera, single-celled organisms roughly the size of the period ending this sentence, occur nearly everywhere in the oceans and have an exquisite fossil record."
Especially Figure 2 on that page, a map showing the change in Sea Surface Temperature, was interesting.
Do you have more information on what changed around 1945? (I mean, I could probably guess. I was wondering if you're looking at different sources than I am.)