In the "Plankton cooled a greenhouse", which is the article written by Birger Schmitz, it is stated that the subtropical regions became warmer during the PETM(Paleocene/Eocene Thermal Maximum) but the temperature elevation was greater in the polar region. (https://www.nature.com/articles/35025173)
This is evident from the oxygen isotope(18-Oxygen/16-Oxygen) data which can be obtained from the sediments of higher latitudes and lower latitudes.
However, I want to know why the temperature change was greater in higher latitudes than in lower latitudes. This tendency does not seem to be regional, but global so there should be something reasonable to explain this.
If you come through a good schematic explanation or have a good reference to read, I would obviously want to know it.