Tipping point

A threshold beyond which a system shifts toward a substantially different state. The shift may become self-reinforcing and difficult to reverse.

Positive feedback: A process in which an initial change amplifies itself through its effects. Self-amplifying feedback can drive a system past a tipping point.
Atlantic meridional overturning circulation: A system of Atlantic Ocean currents that transports heat northward and returns cold, deep water southward. Its possible weakening or collapse is a prominent proposed climate tipping element.
Threshold effect: A nonlinear response in which a small change near a boundary produces a disproportionately large effect. It describes the response pattern that makes a tipping threshold consequential.
Climate tipping points: Thresholds in parts of the climate system that could trigger large, persistent changes. Their locations, interactions, and likelihoods remain uncertain despite growing evidence.
Precautionary principle: A policy approach that supports protective action when serious harm is plausible despite scientific uncertainty. Potentially irreversible thresholds strengthen arguments for acting before certainty arrives.
Bifurcation theory: The mathematical study of qualitative changes in a system as parameters vary. It describes how changing conditions can create sudden transitions between system behaviors.
Greenland ice sheet: A vast body of ice covering Greenland, whose melting contributes to sea-level rise. Ice loss can reinforce warming and may pass a threshold toward long-term decay.
Nonlinear system: A system whose output is not proportional to its inputs. Tipping behavior depends on nonlinear relationships between pressures and responses.
Early warning signal: An observable change that may indicate an approaching transition in a system. Researchers test whether such signals can provide reliable warning before a threshold is crossed.
Climate change mitigation: Actions that reduce greenhouse-gas emissions or increase their removal from the atmosphere. Mitigation can lower the chance of crossing climate-system thresholds.

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