Flat meridional temperature gradient in the early Eocene in the subsurface rather than surface ocean

Sea surface temperature estimates from the early Eocene indicate an unusually flat meridional temperature gradient. A re-evaluation of the proxy used to derive these temperatures argues against this interpretation. The early Eocene (49–55 million years ago) is a time interval characterized by elevated surface temperatures and atmospheric CO2 (refs 1,2), and a flatter-than-present latitudinal surface temperature gradient3,4. The...