Lenton, T. M., H. Held, E. Kriegler, J. W. Hall, W. Lucht, S. Rahmstorf, and H. J. Schellnhuber. 2008. Tipping elements in the Earth’s climate system. Proceedings of the National Academy of Sciences 105(6):1786-1793.

2.3.2.2 ANALYSIS: CAUSES, CONSEQUENCE, PROCESSES: Interaction, Impacts, Response - Limits, boundaries, thresholds, and tipping points In nature, rapid phase transitions are common, as in the tiny increment of cooling that turns water into ice. But in human-environment systems, rapid phase transitions are feared, especially if they are poorly understood. So a search for limits (see also 1.4.1.2), dangerous thresholds, and tipping points consume a significant set of scientific attention. A search for “safety” limits for the earth’s life-support and ecological systems are long standing and widespread. Much of it has taken the form identifying “carrying capacity” that limits the use of the earth (see also 1.4.1.2), or “critical loads” that overburdens air or water systems or minimal doses that cause harm from radiation or chemical pollutants. And akin to the phase transition is the concern with tipping points beyond which systems spiral into irreversible change. The Reading illustrates this search for limits, thresholds, and tipping points in the global climate system. Nine tipping elements are identified as extensive components of the earth system, subcontinental in size, affected by human-induced climate change, with potential that a small change across a threshold can trigger a substantial qualitative change. These changes are in ice sheets, ocean circulation, and vegetation.

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