[1] The EECO's onset is signified by a major geochemical enrichment in isotopically light carbon, commonly known as a negative δ13C excursion, that demarcates the hyperthermal Eocene Thermal Maximum 3 (ETM3).
[10] Sediments from San Diego County, California record a MAP of 1100 ± 299 mm, notably drier than the region was during the Palaeocene-Eocene Thermal Maximum.
[13] The latitudinal climate gradient is generally believed to have been smaller, which was mainly the result of a decrease in albedo differences across Earth's surface.
[14] Although SSTs are often believed to have had a shallow latitudinal temperature gradient, this is likely to be an artefact of burial-induced oxygen isotope reequilibration in fossilised benthic foraminifera.
[25] Other research attributes the elevated greenhouse gas levels to increased generation of petroleum in sedimentary basins and enhanced ventilation of marine carbon.
[27] The supergreenhouse climate of the EECO fostered extensive floral diversification and increased habitat complexity in North American terrestrial biomes.
[28] The Okanagan Highlands in British Columbia and Washington became a biodiversity hotspot from which newly evolved lineages of temperate-adapted plants radiated from following the end of the EECO.
[38] The central Tethys in what is now northeastern Italy was a hotspot of coral diversity, with its mesophotic deltaic environment acting as a refugium.
[41] The euryhaline dinoflagellate Homotryblium became superabundant at the site of Waipara in New Zealand during the early and middle EECO, reflecting the occurrence of significant stratification of surficial waters as well as increased salinity.
[46] Based on the Representative Concentration Pathway 8.5 (RCP8.5) emission scenario, by 2150 CE, the climates across much of the world would resemble conditions during the EECO.