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

• Published in: Nature Geoscience
• Main Authors: Fischer, Hubertus, Meissner, K.J., Mix, Alan C, Abram, Nerilie, Austermann, Jacqueline, Brovkin, Victor, Capron, Emilie, Colombaroli, Daniele, Daniau, A.-L., Dyez, Kelsey A., Felis, Thomas
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Publishing Group
• Subjects: Antarctic; Greenland; Antarc*
• Online Access: http://hdl.handle.net/1885/251922; https://doi.org/10.1038/s41561-018-0146-0; https://openresearch-repository.anu.edu.au/bitstream/1885/251922/3/01_Fischer_Palaeoclimate_constraints_on_2018.pdf.jpg

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. Financial support of the PAGES Warmer World Integrative Activity workshop by the Future Earth core project PAGES (Past Global Changes) and the Oeschger Centre for Climate Change Research, University of Bern, is gratefully acknowledged. Additional funding by PAGES was provided to the plioVAR, PALSEA 2, QUIGS, the 2k network, C-peat, Global Paleofire 2 and OC3 PAGES working groups contributing to the Integrated Activity (see http://www.pages.unibe.ch/science/intro for an overview of all former and active PAGES working groups).