Palaeoclimate constraints on the impact of 2 °C anthropogenic warming and beyond

Hubertus Fischer (1, 2) , Katrin J. Meissner (3) , Alan C. Mix (4) , Nerilie Abram (5) , Jacqueline Austermann (6) , Victor Brovkin (7) , Emilie Capron (8, 9) , Daniel Colombaroli (2) , Anne Daniau (10) , Kelsey Dyez (11) , Thomas Felis (12) , Sarah Finkelstein (13) , Samuel Jaccard (2) , Erin Mcclymont (14) , Alessio Rovere (12) , Johannes Sutter (15) , Eric Wolff (16) , Stéphane Affolter (1, 2) , Pepijn Bakker (12) , Juan Antonio Ballesteros-Cánovas (17) , Carlo Barbante (18) , Thibaut Caley (19) , Anders E. Carlson (4) , Olga Churakova (17) , Giuseppe Cortese (20) , Brian Cumming (21) , Basil A.S. Davis (22) , Anne de Vernal (23) , Julien Emile-Geay (24) , Sherilyn C. Fritz (25) , Paul Gierz (15) , Julia Gottschalk (2) , Max Holloway (8) , Fortunat Joos (1, 2) , Michal Kucera (12) , Marie-France Loutre (26) , Daniel Lunt (27) , Katarzyna Marcisz (28, 2) , Jennifer Marlon (29) , Matias Martinez (10) , Valérie Masson-Delmotte (30, 31) , Christoph Nehrbass-Ahles (1, 2) , Bette Otto-Bliesner (32) , Christoph Raible (1, 2) , Bjørg Risebrobakken (33) , María Sánchez Goñi (34) , Jennifer Saleem Arrigo (35) , Michael Sarnthein (36) , Jesper Sjolte (37) , Thomas Stocker (1, 2) , Patricio Velasquez Alvárez (1, 2) , Willy Tinner (2) , Paul Valdes (27) , Hendrik Vogel (38, 2) , Heinz Wanner (39, 2) , Qing Yan (40) , Zicheng Yu (41) , Martin Ziegler (42, 43) , Liping Zhou (44)

1 CEP - Climate and Environmental Physics [Bern]
2 OCCR - Oeschger Centre for Climate Change Research
3 CCRC - Climate Change Research Centre [Sydney]
4 CEOAS - College of Earth, Ocean and Atmospheric Sciences [Corvallis]
5 ANU - Australian National University
6 Bullard Laboratories
7 MPI-M - Max Planck Institute for Meteorology
8 BAS - British Antarctic Survey
9 Centre for Ice and Climate [Copenhagen]
10 EPOC - Environnements et Paléoenvironnements OCéaniques
11 LDEO - Lamont-Doherty Earth Observatory
12 MARUM - Center for Marine Environmental Sciences [Bremen]
13 University of Toronto
14 UNIVERSITé DE DURHAM - Department of Geography
15 AWI - Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung
16 CAM - University of Cambridge [UK]
17 UNIGE - Université de Genève = University of Geneva
18 Institute for the Dynamics of Environmental Processes-CNR
19 EPOC - UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux
20 GNS Science [Lower Hutt]
21 Queen's University [Kingston, Canada]
22 Institute of Earth Surface Dynamics [Lausanne]
23 GEOTOP - Centre de recherche sur la dynamique du système Terre
24 USC - University of Southern California
25 University of Nebraska–Lincoln
26 PAGES - Past Global Changes International Project Office
27 School of Geographical Sciences [Bristol]
28 Laboratory of Wetland Ecology and Monitoring
29 School of Forestry and Environmental Studies
30 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
31 GLACCIOS - Glaces et Continents, Climats et Isotopes Stables
32 NCAR - National Center for Atmospheric Research [Boulder]
33 Uni Research Climate
34 PSL - Université Paris sciences et lettres
35 National Coordination Office, Washington
36 Institute of Geosciences [Kiel]
37 Department of Geology, Quaternary Sciences
38 UFZ - Helmholtz Zentrum für Umweltforschung = Helmholtz Centre for Environmental Research
39 Institute of Geography [Bern]
40 NZC - Nansen-Zhu International Research Center
41 Lehigh University [Bethlehem]
42 Department of Earth Sciences [Utrecht]
43 Ecole Polytechnique Fédérale de Zurich
44 University of Peking

Over the past 3.5 million years, there have been several intervals when climate conditions were warmer than during the pre-industrial Holocene. Although past intervals of warming were forced differently than future anthropogenic change, such periods can provide insights into potential future climate impacts and ecosystem feedbacks, especially over centennial-to-millennial timescales that are often not covered by climate model simulations. Our observation-based synthesis of the understanding of past intervals with temperatures within the range of projected future warming suggests that there is a low risk of runaway greenhouse gas feedbacks for global warming of no more than 2 °C. However, substantial regional environmental impacts can occur. A global average warming of 1–2 °C with strong polar amplification has, in the past, been accompanied by significant shifts in climate zones and the spatial distribution of land and ocean ecosystems. Sustained warming at this level has also led to substantial reductions of the Greenland and Antarctic ice sheets, with sea-level increases of at least several metres on millennial timescales. Comparison of palaeo observations with climate model results suggests that, due to the lack of certain feedback processes, model-based climate projections may underestimate long-term warming in response to future radiative forcing by as much as a factor of two, and thus may also underestimate centennial-to-millennial-scale sea-level rise.

Domains: Sciences of the Universe [physics]; Earth Sciences; Sciences of the Universe [physics]; Earth Sciences; Climatology

Hubertus Fischer, Katrin J. Meissner, Alan C. Mix, Nerilie Abram, Jacqueline Austermann, et al.. Palaeoclimate constraints on the impact of 2 °C anthropogenic warming and beyond. Nature Geoscience, 2018, 11 (7), pp.474 - 485. ⟨10.1038/s41561-018-0146-0⟩. ⟨cea-01883055⟩