Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum  (PETM), and latest Paleocene

G. N. Inglis; G. N. Inglis; F. Bragg; N. J. Burls; M. J. Cramwinckel; M. J. Cramwinckel; D. Evans; G. L. Foster; M. Huber; D. J. Lunt; N. Siler; S. Steinig; J. E. Tierney; R. Wilkinson; R. Wilkinson; E. Anagnostou; A. M. de Boer; T. Dunkley Jones; K. M. Edgar; C. J. Hollis; D. K. Hutchinson; R. D. Pancost

doi:10.5194/cp-16-1953-2020

Climate of the Past (Oct 2020)

Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum (PETM), and latest Paleocene

G. N. Inglis,
G. N. Inglis,
F. Bragg,
N. J. Burls,
M. J. Cramwinckel,
M. J. Cramwinckel,
D. Evans,
G. L. Foster,
M. Huber,
D. J. Lunt,
N. Siler,
S. Steinig,
J. E. Tierney,
R. Wilkinson,
R. Wilkinson,
E. Anagnostou,
A. M. de Boer,
T. Dunkley Jones,
K. M. Edgar,
C. J. Hollis,
D. K. Hutchinson,
R. D. Pancost

Affiliations

G. N. Inglis: School of Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, UK
G. N. Inglis: Organic Geochemistry Unit, School of Chemistry, School of Earth Sciences, Cabot Institute for the Environment, University of Bristol, Bristol, UK
F. Bragg: School of Geographical Sciences, University of Bristol, Bristol, UK
N. J. Burls: Department of Atmospheric, Oceanic and Earth Sciences, George Mason University, Fairfax, USA
M. J. Cramwinckel: Department of Earth Sciences, Utrecht University, Utrecht, the Netherlands
M. J. Cramwinckel: currently at: School of Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, UK
D. Evans: Institute of Geosciences, Goethe University Frankfurt, Frankfurt am Main, Germany
G. L. Foster: School of Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton, UK
M. Huber: Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, USA
D. J. Lunt: School of Geographical Sciences, University of Bristol, Bristol, UK
N. Siler: College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, USA
S. Steinig: School of Geographical Sciences, University of Bristol, Bristol, UK
J. E. Tierney: Department of Geosciences, The University of Arizona, 1040 E 4th St., Tucson, USA
R. Wilkinson: School of Mathematics and Statistics, University of Sheffield, Sheffield, UK
R. Wilkinson: currently at: School of Mathematical Sciences, University of Nottingham, Nottingham, UK
E. Anagnostou: GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
A. M. de Boer: Department of Geological Sciences and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
T. Dunkley Jones: School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
K. M. Edgar: School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
C. J. Hollis: GNS Science, Lower Hutt, New Zealand
D. K. Hutchinson: Department of Geological Sciences and Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
R. D. Pancost: Organic Geochemistry Unit, School of Chemistry, School of Earth Sciences, Cabot Institute for the Environment, University of Bristol, Bristol, UK

DOI: https://doi.org/10.5194/cp-16-1953-2020
Journal volume & issue: Vol. 16
pp. 1953 – 1968

Abstract

Read online

Accurate estimates of past global mean surface temperature (GMST) help to contextualise future climate change and are required to estimate the sensitivity of the climate system to CO2 forcing through Earth's history. Previous GMST estimates for the latest Paleocene and early Eocene (∼57 to 48 million years ago) span a wide range (∼9 to 23 ∘C higher than pre-industrial) and prevent an accurate assessment of climate sensitivity during this extreme greenhouse climate interval. Using the most recent data compilations, we employ a multi-method experimental framework to calculate GMST during the three DeepMIP target intervals: (1) the latest Paleocene (∼57 Ma), (2) the Paleocene–Eocene Thermal Maximum (PETM; 56 Ma), and (3) the early Eocene Climatic Optimum (EECO; 53.3 to 49.1 Ma). Using six different methodologies, we find that the average GMST estimate (66 % confidence) during the latest Paleocene, PETM, and EECO was 26.3 ∘C (22.3 to 28.3 ∘C), 31.6 ∘C (27.2 to 34.5 ∘C), and 27.0 ∘C (23.2 to 29.7 ∘C), respectively. GMST estimates from the EECO are ∼10 to 16 ∘C warmer than pre-industrial, higher than the estimate given by the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (9 to 14 ∘C higher than pre-industrial). Leveraging the large “signal” associated with these extreme warm climates, we combine estimates of GMST and CO2 from the latest Paleocene, PETM, and EECO to calculate gross estimates of the average climate sensitivity between the early Paleogene and today. We demonstrate that “bulk” equilibrium climate sensitivity (ECS; 66 % confidence) during the latest Paleocene, PETM, and EECO is 4.5 ∘C (2.4 to 6.8 ∘C), 3.6 ∘C (2.3 to 4.7 ∘C), and 3.1 ∘C (1.8 to 4.4 ∘C) per doubling of CO2. These values are generally similar to those assessed by the IPCC (1.5 to 4.5 ∘C per doubling CO2) but appear incompatible with low ECS values (<1.5 per doubling CO2).

Published in Climate of the Past

ISSN: 1814-9324 (Print); 1814-9332 (Online)
Publisher: Copernicus Publications
Country of publisher: Germany
LCC subjects: Technology: Environmental technology. Sanitary engineering: Environmental pollution; Technology: Environmental technology. Sanitary engineering: Environmental protection; Geography. Anthropology. Recreation: Environmental sciences
Website: https://www.climate-of-the-past.net/index.html

About the journal