Tropical sea temperatures in the high-latitude South Pacific during the Eocene

Sea-surface temperature (SST) estimates of similar to 30 degrees C from planktic foraminifera and archaeal membrane lipids in bathyal sediments in the Canterbury Basin, New Zealand, support paleontological evidence for a warm subtropical to tropical climate in the early Eocene high-latitude (55 degrees S) southwest Pacific. Such warm SSTs; call into quest-ion previous estimates based on oxygen isotopes and present a major challenge to climate modelers. Even under hypergreenhouse conditions (2240 ppm CO2), modeled summer SSTs for the New Zealand region do not exceed 20 degrees C.