https://onlinelibrary.wiley.com/doi/full/10.1111/pce.14060 https://www.livescience.com/planet-earth/plants/tropical-rai...
And the planet may well have been warmer in the past, but the ecosystems had millions of years to adapt to it.
Also, your geological timelines are way off. Last interglacial period (with temperatures higher than today) was 100k years ago.
HN has literally became an anti-intellectual echo-chamber.
> The Last Interglacial climate is believed to have been warmer than the current Holocene.
> During the northern summer, temperatures in the Arctic region were about 2–4 °C higher than in 2011
The Climate heading in this article will give a little overview https://en.wikipedia.org/wiki/Cenozoic
See also the plot here https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Therm...