Tropical mountain ice core δ 18 O: A Goldilocks indicator for global temperature change

• Published in: Science Advances
• Main Authors: Liu, Zhengyu, Bao, Yuntao, Thompson, Lonnie G., Mosley-Thompson, Ellen, Tabor, Clay, Zhang, Guang J., Yan, Mi, Lofverstrom, Marcus, Montanez, Isabel, Oster, Jessica
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Association for the Advancement of Science (AAAS) 2023
• Subjects: ice core
• Online Access: http://dx.doi.org/10.1126/sciadv.adi6725; https://www.science.org/doi/pdf/10.1126/sciadv.adi6725

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.