The Antartic had ferns and trees at one time. Ferns are tropical and semi-tropical, by the way. Humans are puny and a blip on the universe. We are laughable when we talk about causing climate change.
If it is true that the entire planet, pre-human, was tropical then why, oh why, would any scientist say humans are dangerously changing the climate? Is it possible that climate change is a manufactured crisis with a political agenda?