Last Glacial Maximum pattern effects reduce climate sensitivity estimates

Cooper, V. T., Armour, K. C., Hakim, G. J., Tierney, J. E., Osman, M. B., et al. (2024). Last Glacial Maximum pattern effects reduce climate sensitivity estimates. Science Advances, doi:10.1126/sciadv.adk9461

Title Last Glacial Maximum pattern effects reduce climate sensitivity estimates
Author(s) Vincent T. Cooper, Kyle C. Armour, Gregory J. Hakim, Jessica E. 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 degrees C, 66% range 1.7 degrees to 3.5 degrees C (1.4 degrees to 5.0 degrees C, 5 to 95%), from LGM evidence alone. Combining the LGM with other lines of evidence, the best estimate becomes 2.9 degrees C, 66% range 2.4 degrees to 3.5 degrees C (2.1 degrees to 4.1 degrees C, 5 to 95%), substantially narrowing uncertainty compared to recent assessments.
Publication Title Science Advances
Publication Date Apr 19, 2024
Publisher's Version of Record https://dx.doi.org/10.1126/sciadv.adk9461
OpenSky Citable URL https://n2t.net/ark:/85065/d7hh6q8h
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