Yeah, it’s funny they choose 1979 as a base to start from. Especially considering temperature data do go back a LOT further.
Why 1979 ?
That dreaded and predicted Ice Age of the early 70’s never happened and busy-body scientists had to concoct a reason.
Coincidentally, ‘79 was the first year of satellite technology which enabled accurate temp. recording.
Thank our lucky stars we live at a time of moderate climate as we slowly exit the ICE AGE.