Recent research by human scientists into polar ice cores have revealed that a few thousand years ago the ice caps experienced a rapid increase in temperature, at time up to 50 to 70 degrees, and this over a few months or years. Of course the temperature did not rise such that poles were experiencing an increase to this degree, else what would the temperature have been at the equator? Your equator would have been cooked, with a massive die-off. The animal and plant species, the fauna and flora, would have thereafter been from the temperate regions, growing into the equator. Is this what your Earth presents? Obviously your tropical forests have been around for eons. They are well established. Fossils show their progression. They did not die out, nor did they spring forth within the last mere 12,000 years.
The analysis is correct, and the physical evidence undeniable, but the conclusions are flawed. The Earths crust moved, such that the poles, where they were placed 12,000 years ago (and this human estimate is not an accurate year measure), shifted to a slightly warmer position. If the poles were to be in mid-Canada, for instance, for a period of time, and then shift back to where the poles are today, the ice cores would represent such a change. Your frozen mastodons, within the polar circle, have grass within their bellies, showing that they grazed meadows at one point in the recent past, within 10,000 years or so as human scientists have estimated. This falls nicely in line with this new evidence. The crust does shift, and this accounts for wandering poles, and thus the evidence makes sense. You will not see such a temperature rise. Most certainly not.