Record-Setting Ocean Warmth Continued in 2019, page-17

Lapdog, here’s a link that explains it.

“Temperature records from thermometers and weather stations exist only for a tiny portion of our planet's 4.54-billion-year-long life. By studying indirect clues—the chemical and structural signatures of rocks, fossils, and crystals, ocean sediments, fossilized reefs, tree rings, and ice cores—however, scientists can infer past temperatures.”

https://www.climate.gov/news-features/climate-qa/whats-hottest-earths-ever-been
They don’t explain how it’s all the fault of Sir Keith Murdoch but I’m sure you can attempt to try.