|It's changed a bit since...|
On the other hand, there were times when the world was much hotter than today, warm enough that there appear to have been no ice caps at all, even at the poles. During the Age of Mammals - the eon of time since the extinction of the non-avian dinosaurs - the hottest of these was the Eocene Climactic Optimum. This took place a little over 50 million years ago, and it lasted rather a long time, punctuated by short periods of even greater heat. (That's 'short' as in they lasted tens of thousands of years, but not millions).