The tropics temperature increased by only about 5 degrees Celsius while the North Pole increased by 43 degrees.
Clearly there is something wrong with the analysis. When things don't add up, then there is an error.
Perhaps the area sampled was farther South than they thought at the time and was also a shallow freshwater sea rather than ocean. Much of central North America was a shallow sea at the time. Perhaps this now Arctic ocean and Arctic plate location was tied into it at the time. That might explain it better.
55 Million Years ago, there was no Isthmus of Panama and a much less constrained Drake Passage. The ocean currents circled the Globe at the Equator and there was no Gulf Stream. I would imagine the climate to have been drastically different. To compare 55 million years ago with now (or with the next 1000 years) is apples and oranges. This tells us precisely nothing about what to expect assuming arthropgenic global warming is even happening at all.
How does the theory that at one time the earth flopped 90 degrees, putting the north pole at the equator?
Would not an increase in atmospheric water vapor induced by such elevated temperatures serve as an equalizing blanket to more evenly distribute atmospheric heat over the planetary surface?
It seems to me that increasing the global average temperature would increase evaporative activity over the oceanic surfaces, driving more water vapor into the atmosphere. That increase humidity would increase the thermal conductivity of the atmosphere, while also increasing the incidence and size of clouds at all altitudes. Both taken together might well have a blanketing effect that, like the roof on a greenhouse, would serve to distribute local heat over a far greater area of the globe with an equalizing effect.