Modest, not extreme, northern high latitude amplification during the Miocene shown by coccolith clumped isotopes

Luz Maria Mejia Ramirez, Stefano M. Bernasconi, Alvaro Fernandez, Hongrui Zhang, José Guitián, Madalina Jaggi, Victoria Emma Taylor, Alberto Perez-Huerta, Heather M. Stoll

Accurate predictions of the future climate response to CO₂ depend on the ability of climate models to simulate past analog warmer climates, like the Miocene. However, one key unresolved issue in paleoclimate modeling is reproducing the pronounced high-latitude warmth and relatively flat latitudinal temperature gradients inferred from proxy records. Here, we use clumped isotope thermometry—a method that sidesteps limitations of conventional proxies—on pure coccolith calcite from a high-latitude North Atlantic site, extending from the Mid Miocene to the Quaternary. Coccolith-derived clumped isotope temperatures are on average ~9 °C lower than alkenone estimates, representing the first proxy dataset to align with Miocene model outputs and calling into question the prevailing paradigm of pronounced high latitude amplification. This record highlights the need to continuously reevaluate proxy interpretations to achieve both reliable trends and absolute temperature values, while providing a more optimistic perspective of future high latitude climate response to CO₂ emissions.