Last Glacial Maximum pattern effects reduce climate sensitivity estimates

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1126/sciadv.adk9461. This is version 4 of this Preprint.

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Authors

Vincent T. Cooper , Kyle C. Armour, Greg Hakim , Jessica Tierney , Matthew B Osman, Cristian Proistosescu, Yue Dong, Natalie J. Burls, Timothy Andrews, Daniel E. Amrhein, Jiang Zhu, Wenhao Dong, Yi Ming, Philip Chmielowiec

Abstract

Here, we show that the Last Glacial Maximum (LGM) provides a stronger constraint on equilibrium climate sensitivity (ECS), the global warming from increasing greenhouse gases, after accounting for temperature patterns. Feedbacks governing ECS depend on spatial patterns of surface temperature (“pattern effects”); hence, using the LGM to constrain future warming requires quantifying how temperature patterns produce different feedbacks during LGM cooling versus modern-day warming. Combining data assimilation reconstructions with atmospheric models, we show that the climate is more sensitive to LGM forcing because ice sheets amplify extratropical cooling where feedbacks are destabilizing. Accounting for LGM pattern effects yields a median modern-day ECS of 2.4°C, 66% range 1.7° to 3.5°C (1.4° to 5.0°C, 5 to 95%), from LGM evidence alone. Combining the LGM with other lines of evidence, the best estimate becomes 2.9°C, 66% range 2.4° to 3.5°C (2.1° to 4.1°C, 5 to 95%), substantially narrowing uncertainty compared to recent assessments.

DOI

https://doi.org/10.31223/X5VD56

Subjects

Atmospheric Sciences, Climate, Oceanography, Oceanography and Atmospheric Sciences and Meteorology

Keywords

Last Glacial Maximum, Climate sensitivity, Pattern effect, climate feedbacks, radiative feedbacks, data assimilation

Dates

Published: 2023-07-13 23:51

Last Updated: 2024-04-24 16:28

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License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
None