Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum, Paleocene Eocene thermal Maximum, and latest Paleocene

Research output: Contribution to journalArticle

Authors

  • Gordan Inglis
  • Fran Bragg
  • Natalie Burls
  • Margot J. Cramwinckel
  • David Evans
  • Gavin L. Foster
  • Matthew Huber
  • Dan J. Lunt
  • Nicholas Siler
  • Sebastian Steinig
  • Jessica Tierney
  • Richard Wilkinson
  • Eleni Anagnostou
  • A De Boer
  • Chris Hollis
  • David Hutchinson
  • Richard D. Pancost

Colleges, School and Institutes

Abstract

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 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 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 (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).

Details

Original languageEnglish
Pages (from-to)1953-1968
JournalClimate Of The Past
Volume16
Issue number5
Publication statusPublished - 26 Oct 2020