@article{49e3752d0db347ac8d46ef5d754d14d1,
title = "Last Glacial Maximum pattern effects reduce climate sensitivity estimates",
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.",
author = "Cooper, {Vincent T.} and Armour, {Kyle C.} and Hakim, {Gregory J.} and Tierney, {Jessica E.} and Osman, {Matthew B.} and Cristian Proistosescu and Yue Dong and Burls, {Natalie J.} and Timothy Andrews and Amrhein, {Daniel E.} and Jiang Zhu and Wenhao Dong and Yi Ming and Philip Chmielowiec",
note = "V.T.C. acknowledges support from the US Department of Defense through a National Defense Science and Engineering Graduate (NDSEG) Fellowship and high-performance computing support from Cheyenne (doi:10.5065/D6RX99HX) provided by the Computational and Information Systems Laboratory at the National Science Foundation (NSF) National Center for Atmospheric Research (NCAR). The Community Earth System Model (CESM) project is supported primarily by the NSF. This material is based on work supported by the NSF National Center for Atmospheric Research, which is a major facility sponsored by the NSF under Cooperative Agreement No. 1852977. V.T.C. thanks C. Bitz, D. Hartmann, A. Donohoe, D. Battisti, and anonymous reviewers for thoughtful discussions and comments. Funding: This work was supported by the following: National Defense Science and Engineering Graduate (NDSEG) Fellowship, US Department of Defense (V.T.C.); National Science Foundation award OCE-2002276 (V.T.C., K.C.A., and G.J.H.); National Oceanic and Atmospheric Administration MAPP Program award NA20OAR431039 (K.C.A. and C.P.); Alfred P. Sloan Research Fellowship grant FG-2020-13568 (K.C.A.); a Calvin Professorship in Oceanography (K.C.A.); National Science Foundation award OCE-2002398 (J.E.T. and M.B.O.); National Science Foundation award OCE-2002385 (C.P. and P.C.); National Science Foundation award OCE-2002448 (N.J.B.); National Science Foundation award AGS-1844380 (N.J.B.); National Oceanic and Atmospheric Administration, Climate & Global Change Postdoctoral Fellowship Program, administered by UCAR\u2019s Cooperative Programs for the Advancement of Earth System Science (CPAESS) under award NA210AR4310383 (Y.D.); Met Office Hadley Centre Climate Programme funded by Business, Energy and Industrial Strategy (T.A.); and the European Union\u2019s Horizon 2020 Research and Innovation Programme under grant agreement 820829 (T.A.). Acknowledgments: v.t.C. acknowledges support from the US department of defense through a national defense Science and engineering Graduate (ndSeG) Fellowship and high-performance computing support from Cheyenne (doi:10.5065/d6RX99hX) provided by the Computational and information Systems laboratory at the national Science Foundation (nSF) national Center for Atmospheric Research (nCAR). the Community earth System Model (CeSM) project is supported primarily by the nSF. this material is based on work supported by the nSF national Center for Atmospheric Research, which is a major facility sponsored by the nSF under Cooperative Agreement no. 1852977. v.t.C. thanks C. Bitz, d. hartmann, A. donohoe, d. Battisti, and anonymous reviewers for thoughtful discussions and comments. Funding: this work was supported by the following: national defense Science and engineering Graduate (ndSeG) Fellowship, US department of defense (v.t.C.); national Science Foundation award OCe-2002276 (v.t.C., K.C.A., and G.J.h.); national Oceanic and Atmospheric Administration MAPP Program award nA20OAR431039 (K.C.A. and C.P.); Alfred P. Sloan Research Fellowship grant FG-2020-13568 (K.C.A.); a Calvin Professorship in Oceanography (K.C.A.); national Science Foundation award OCe-2002398 (J.e.t. and M.B.O.); national Science Foundation award OCe-2002385 (C.P. and P.C.); national Science Foundation award OCe-2002448 (n.J.B.); national Science Foundation award AGS-1844380 (n.J.B.); national Oceanic and Atmospheric Administration, Climate & Global Change Postdoctoral Fellowship Program, administered by UCAR\u2019s Cooperative Programs for the Advancement of earth System Science (CPAeSS) under award nA210AR4310383 (Y.d.); Met Office hadley Centre Climate Programme funded by Business, energy and industrial Strategy (t.A.); and the european Union\u2019s horizon 2020 Research and innovation Programme under grant agreement 820829 (t.A.). Author contributions: v.t.C. performed the analysis, designed the simulations, wrote the original draft, and ran the simulations in CAM5 and CAM4. K.C.A. initiated the study with support from G.J.h., C.P., J.e.t., and n.J.B. K.C.A. and G.J.h. supervised the research. G.J.h., J.e.t., M.B.O., and d.e.A. contributed expertise on data assimilation and lGM reconstructions. Y.d., n.J.B., t.A., C.P., J.Z., and Y.M. contributed to analysis and interpreting results. t.A. ran AGCM simulations in hadGeM3-GC3.1-ll, W.d. in GFdl-AM4, and P.C. in CAM6. J.Z. provided coupled simulations in CeSM. All authors contributed to editing the paper. Competing interests: the authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. SSt/SiC boundary conditions and AGCM results are available at github.com/vtcooper/cooper_etal_2024_lGMpattern or on Zenodo at doi.org/10.5281/ zenodo.10651822. longRunMiP is available at longrunmip.org, lGMR (32) at doi.org/10.25921/ njxd-hg08, lgmdA (3) v2.1 at doi.org/10.5281/zenodo.5171432, Amrhein (34) at doi. org/10.5281/zenodo.8110710, and Annan (33) at doi.org/10.5194/cp-18-1883-2022. Previous studies\u2019coupled model outputs are hosted at doi.org/10.5281/zenodo.3948405 (CeSM1-CAM5) (23), doi.org/10.5281/zenodo.4075596 (CeSM2-CAM6) (48), and doi.org/10.5065/ bdr7-wt42 (CeSM2-PaleoCalibr) (49). Code from WCRP20 to calculate climate sensitivity is available at doi.org/10.5281/zenodo.3945276 (78). CAM5 radiative kernels are available through doi.org/10.5281/zenodo.3359041 (77).",
year = "2024",
doi = "10.1126/sciadv.adk9461",
language = "English (US)",
volume = "10",
journal = "Science Advances",
issn = "2375-2548",
publisher = "American Association for the Advancement of Science",
number = "16",
}