"...and assuming that the Earth wasn't closer to the Sun 65 million years ago. ;')"
But would it have been more hot on this planet if it was closer to the Sun? What if the atmosphere was 'different'?
I think I see what you mean though...Earth did 'sink beneath its wonted place' by 'two hand's breadth' and that must have been quite a distance. (And that wasn't 65 million years ago!)
There's another story floating around regarding the possible growth of trees on Antarctica, and another regurgitation of the false idea that Antarctica has been ice covered for (in this version) 40 million years. Antarctica was temperate less than three million years ago.
The Earth's in prograde orbit around the Sun. Assuming that to have been the case right along :') there will have been a transfer of momentum through tidal forces, meaning the Earth is slowing but surely spiraling its way away from the Sun (likewise the other planets).