Tropical mountain ice core δ <sup>18</sup> O: A Goldilocks indicator for global temperature change
Zhengyu Liu, Yuntao Bao, Lonnie G. Thompson, Ellen Mosley‐Thompson, Clay Tabor, Guang J. Zhang, Mi Yan, Marcus Löfverström, Isabel P. Montañez, Jessica Oster
Abstract
Very high tropical alpine ice cores provide a distinct paleoclimate record for climate changes in the middle and upper troposphere. However, the climatic interpretation of a key proxy, the stable water oxygen isotopic ratio in ice cores (δ 18 O ice ), remains an outstanding problem. Here, combining proxy records with climate models, modern satellite measurements, and radiative-convective equilibrium theory, we show that the tropical δ 18 O ice is an indicator of the temperature of the middle and upper troposphere, with a glacial cooling of −7.35° ± 1.1°C (66% CI). Moreover, it severs as a “Goldilocks-type” indicator of global mean surface temperature change, providing the first estimate of glacial stage cooling that is independent of marine proxies as −5.9° ± 1.2°C. Combined with all estimations available gives the maximum likelihood estimate of glacial cooling as −5.85° ± 0.51°C.