Climatic Change

, Volume 65, Issue 1, pp 11-38

Nonlinearities, Feedbacks and Critical Thresholds within the Earth's Climate System

  • José A. RialAffiliated withWave Propagation Laboratory, Department of Geological Sciences CB#3315, University of North Carolina
  • , Roger A. PielkeSr.Affiliated withAtmospheric Science Dept., Colorado State University
  • , Martin BenistonAffiliated withDept. of Geosciences, Geography, Univ. of Fribourg
  • , Martin ClaussenAffiliated withPotsdam Institute for Climate Impact Research
  • , Josep CanadellAffiliated withGCP-IPO, Earth Observation Centre, CSIRO
  • , Peter CoxAffiliated withMet Office Hadley Centre
  • , Hermann HeldAffiliated withPotsdam Institute for Climate Impact Research
  • , Nathalie de Noblet-DucoudréAffiliated withDSM/LSCE, Laboratoire des Sciences du Climat et de l'Environnement, Unité mixte de Recherche CEA-CNRS
  • , Ronald PrinnAffiliated withDept. of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology
    • , James F. ReynoldsAffiliated withDepartment of Biology and Nicholas School of the Environmental and Earth Sciences, Phytotron Bldg., Science Dr., Duke University
    • , José D. SalasAffiliated withWave Propagation Laboratory, Department of Geological Sciences CB#3315, University of North CarolinaDept. of Civil Engineering, Colorado State University

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The Earth's climate system is highly nonlinear: inputs and outputs are not proportional, change is often episodic and abrupt, rather than slow and gradual, and multiple equilibria are the norm. While this is widely accepted, there is a relatively poor understanding of the different types of nonlinearities, how they manifest under various conditions, and whether they reflect a climate system driven by astronomical forcings, by internal feedbacks, or by a combination of both. In this paper, after a brief tutorial on the basics of climate nonlinearity, we provide a number of illustrative examples and highlight key mechanisms that give rise to nonlinear behavior, address scale and methodological issues, suggest a robust alternative to prediction that is based on using integrated assessments within the framework of vulnerability studies and, lastly, recommend a number of research priorities and the establishment of education programs in Earth Systems Science. It is imperative that the Earth's climate system research community embraces this nonlinear paradigm if we are to move forward in the assessment of the human influence on climate.