We actually have a long way to warm up before we reach “historic” temperatures. And it is all Antarctica’s fault.
Before Antarctica broke free from South America, you didn’t have polar water currents that fueled polar air currents. Once it was free, those polar currents formed and caused a place akin to modern Alaska to grow colder and grow miles thick ice sheets. This pulled the PLANET’s temperature down 10°F at least.
Before that, there were only tropical and semi-tropical climate systems on the planet barring deserts and swamps. There was no tundra or taiga. Ice ages probably occurred but were just spring-like versus freezing.
We’ll know we’ve warmed to historic norms when there is no ice at the south pole, just like it was when the dinosaurs ran around.
The breakup of the pre-Pangea supercontinent Rhodinia is believed responsible for the end of “Snowball Earth” and the subsequent “”Cambrian Explosion”, the sudden appearance of more varied and complex life forms.