Tibetan plateau aridification linked to global cooling at the Eocene–Oligocene transition

Local climate goes global The Eocene–Oligocene transition, about 33.5 million years ago, was a major global climate event. The end of the Eocene was unusually warm with no significant ice on Antarctica but the Oligocene saw the arrival of a permanent Antarctic ice-sheet. Two papers this week relate to the continental effects of this global change. Dupont-Nivet et al. examined sedimentary records from the Tibetan plateau and find a drop in atmospheric water, which caused cooling and aridification coincident with Antarctic cooling. Previous studies attributed this phenomenon to the rapid uplift of the Tibetan plateau, but this new work suggests that regional Tibetan climate was influenced by global events. In an unrelated paper on the same climate transition, Zanazzi et al. explore the cooling in North America at the time. Using stable isotope measurements from fossil teeth and bones to create a proxy temperature record, they find a large drop in mean annual temperature of 8.2 °C — a greater fall than seen in the oceans. This continental transition may explain why many cold-blooded reptiles and amphibians became extinct whereas mammals — able to regulate their body temperature — escaped relatively unscathed.