Abstract

We explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced. Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene. We examine the evidence that such a threshold might exist and where it might be. If the threshold is crossed, the resulting trajectory would likely cause serious disruptions to ecosystems, society, and economies. Collective human action is required to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state. Such action entails stewardship of the entire Earth System—biosphere, climate, and societies—and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values.

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Acknowledgments

We thank the three reviewers for their comments on the first version of the manuscript and two of the reviewers for further comments on a revised version of the manuscript. These comments were very helpful in the revisions. We thank a member of the PNAS editorial board for a comprehensive and very helpful review. W.S. and C.P.S. are members of the Anthropocene Working Group. W.S., J.R., K.R., S.E.C., J.F.D., I.F., S.J.L., R.W. and H.J.S. are members of the Planetary Boundaries Research Network PB.net and the Earth League’s EarthDoc Programme supported by the Stordalen Foundation. T.M.L. was supported by a Royal Society Wolfson Research Merit Award and the European Union Framework Programme 7 Project HELIX. C.F. was supported by the Erling–Persson Family Foundation. The participation of D.L. was supported by the Haury Program in Environment and Social Justice and National Science Foundation (USA) Decadal and Regional Climate Prediction using Earth System Models Grant 1243125. S.E.C. was supported in part by Swedish Research Council Formas Grant 2012-742. J.F.D. and R.W. were supported by Leibniz Association Project DOMINOES. S.J.L. receives funding from Formas Grant 2014-589. This paper is a contribution to European Research Council Advanced Grant 2016, Earth Resilience in the Anthropocene Project 743080.

Supporting Information

Appendix (PDF)

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Information & Authors

Information

Published in

Go to Proceedings of the National Academy of Sciences
Go to Proceedings of the National Academy of Sciences
Proceedings of the National Academy of Sciences
Vol. 115 | No. 33
August 14, 2018
PubMed: 30082409

Classifications

Submission history

Published online: August 6, 2018
Published in issue: August 14, 2018

Keywords

  1. Earth System trajectories
  2. climate change
  3. Anthropocene
  4. biosphere feedbacks
  5. tipping elements

Acknowledgments

We thank the three reviewers for their comments on the first version of the manuscript and two of the reviewers for further comments on a revised version of the manuscript. These comments were very helpful in the revisions. We thank a member of the PNAS editorial board for a comprehensive and very helpful review. W.S. and C.P.S. are members of the Anthropocene Working Group. W.S., J.R., K.R., S.E.C., J.F.D., I.F., S.J.L., R.W. and H.J.S. are members of the Planetary Boundaries Research Network PB.net and the Earth League’s EarthDoc Programme supported by the Stordalen Foundation. T.M.L. was supported by a Royal Society Wolfson Research Merit Award and the European Union Framework Programme 7 Project HELIX. C.F. was supported by the Erling–Persson Family Foundation. The participation of D.L. was supported by the Haury Program in Environment and Social Justice and National Science Foundation (USA) Decadal and Regional Climate Prediction using Earth System Models Grant 1243125. S.E.C. was supported in part by Swedish Research Council Formas Grant 2012-742. J.F.D. and R.W. were supported by Leibniz Association Project DOMINOES. S.J.L. receives funding from Formas Grant 2014-589. This paper is a contribution to European Research Council Advanced Grant 2016, Earth Resilience in the Anthropocene Project 743080.

Notes

This article is a PNAS Direct Submission.

Authors

Affiliations

Will Steffen1 [email protected]
Stockholm Resilience Centre, Stockholm University, 10691 Stockholm, Sweden;
Fenner School of Environment and Society, The Australian National University, Canberra, ACT 2601, Australia;
Johan Rockström
Stockholm Resilience Centre, Stockholm University, 10691 Stockholm, Sweden;
Center for Macroecology, Evolution, and Climate, University of Copenhagen, Natural History Museum of Denmark, 2100 Copenhagen, Denmark;
Timothy M. Lenton
Earth System Science Group, College of Life and Environmental Sciences, University of Exeter, EX4 4QE Exeter, United Kingdom;
Carl Folke
Stockholm Resilience Centre, Stockholm University, 10691 Stockholm, Sweden;
The Beijer Institute of Ecological Economics, The Royal Swedish Academy of Science, SE-10405 Stockholm, Sweden;
Diana Liverman
School of Geography and Development, The University of Arizona, Tucson, AZ 85721;
Colin P. Summerhayes
Scott Polar Research Institute, Cambridge University, CB2 1ER Cambridge, United Kingdom;
Anthony D. Barnosky
Jasper Ridge Biological Preserve, Stanford University, Stanford, CA 94305;
Sarah E. Cornell
Stockholm Resilience Centre, Stockholm University, 10691 Stockholm, Sweden;
Earth and Life Institute, Université catholique de Louvain, 1348 Louvain-la-Neuve, Belgium;
Belgian National Fund of Scientific Research, 1000 Brussels, Belgium;
Jonathan F. Donges
Stockholm Resilience Centre, Stockholm University, 10691 Stockholm, Sweden;
Research Domain Earth System Analysis, Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany;
Ingo Fetzer
Stockholm Resilience Centre, Stockholm University, 10691 Stockholm, Sweden;
Steven J. Lade
Stockholm Resilience Centre, Stockholm University, 10691 Stockholm, Sweden;
Fenner School of Environment and Society, The Australian National University, Canberra, ACT 2601, Australia;
Marten Scheffer
Department of Environmental Sciences, Wageningen University & Research, 6700AA Wageningen, The Netherlands;
Ricarda Winkelmann
Research Domain Earth System Analysis, Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany;
Department of Physics and Astronomy, University of Potsdam, 14469 Potsdam, Germany
Hans Joachim Schellnhuber1 [email protected]
Stockholm Resilience Centre, Stockholm University, 10691 Stockholm, Sweden;
Research Domain Earth System Analysis, Potsdam Institute for Climate Impact Research, 14473 Potsdam, Germany;
Department of Physics and Astronomy, University of Potsdam, 14469 Potsdam, Germany

Notes

1
To whom correspondence may be addressed. Email: [email protected] or [email protected].
Author contributions: W.S., J.R., K.R., T.M.L., C.F., D.L., C.P.S., A.D.B., S.E.C., M.C., J.F.D., I.F., S.J.L., M.S., R.W., and H.J.S. wrote the paper.

Competing Interests

The authors declare no conflict of interest.

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    Trajectories of the Earth System in the Anthropocene
    Proceedings of the National Academy of Sciences
    • Vol. 115
    • No. 33
    • pp. 8227-E7886

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