[Fraxinus]

This sentence confused me: Oceans and global temperatures are closely linked. Warmer ocean waters result in warmer air temperatures and vice versa.
In the more tropical environs of the Eocene, ocean circulation was weaker and currents more diffuse.
As a result, heat was more evenly distributed around the world. That resulted in fairly mild ocean temperatures worldwide.
Today, ocean temperatures vary considerably and redistribute warm and cold water around the globe.

I thought that weaker currents moved energy slower, resulting in greater temperature differentials?

[decimon]

It is confusing and I don’t think they can adequately cover it in a press release.

I think it all depends on what point in time you begin the discussion. For this they start at a time of relatively warm temperatures, worldwide.

My puny speculation is that there may have been times when the planet as a whole was warmer or cooler but probably more times when global temperatures were distributed more and less evenly.

They mention less ocean circulation. From that I imagine colder waters more staying deep and warmer waters more staying on the surface. If that imagining should be correct then the entire surface of the planet would have been warmer.

And there you have some speculation from a rank amateur. :-)