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

Summary, in English

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.

• Author: Hubertus Fischer; Katrin J. Meissner; Alan C. Mix; Nerilie J. Abram; Jacqueline Austermann; Victor Brovkin; Emilie Capron; Daniele Colombaroli; Anne Laure Daniau; Kelsey A. Dyez; Thomas Felis; Sarah A. Finkelstein; Samuel L. Jaccard; Erin L. McClymont; Alessio Rovere; Johannes Sutter; Eric W. Wolff; Stéphane Affolter; Pepijn Bakker; Juan Antonio Ballesteros-Cánovas; Carlo Barbante; Thibaut Caley; Anders E. Carlson; Olga Churakova (Sidorova); Giuseppe Cortese; Brian F. Cumming; Basil A.S. Davis; Anne de Vernal; Julien Emile-Geay; Sherilyn C. Fritz; Paul Gierz; Julia Gottschalk; Max D. Holloway; Fortunat Joos; Michal Kucera; Marie France Loutre; Daniel J. Lunt; Katarzyna Marcisz; Jennifer R. Marlon; Philippe Martinez; Valerie Masson-Delmotte; Christoph Nehrbass-Ahles; Bette L. Otto-Bliesner; Christoph C. Raible; Bjørg Risebrobakken; María F. Sánchez Goñi; Jennifer Saleem Arrigo; Michael Sarnthein; Jesper Sjolte; Thomas F. Stocker; Qing Yan; Zicheng Yu; Martin Ziegler; Liping Zhou
• Department/s: Quaternary Sciences; MERGE: ModElling the Regional and Global Earth System; BECC: Biodiversity and Ecosystem services in a Changing Climate
• Publishing year: 2018-07
• Language: English
• Pages: 474-485
• Publication/Series: Nature Geoscience
• Volume: 11
• Issue: 7
• Links: http://dx.doi.org/10.1038/s41561-018-0146-0
• Document type: Journal article
• Publisher: Nature Publishing Group
• Topic: Climate Research; Geology
• Status: Published
• ISBN/ISSN/Other: ISSN: 1752-0894