Critical transition
Critical transitions are abrupt shifts in the state of ecosystems, the climate, financial systems or other complex dynamical systems that may occur when changing conditions pass a critical or bifurcation point. As such, they are a particular type of regime shift. Recovery from such shifts may require more than a simple return to the conditions at which a transition occurred, a phenomenon called hysteresis. Early-warning signals and critical slowing down. Significant efforts have been made to identify early-warning signals of critical transitions. Systems approaching a bifurcation point show a characteristic behaviour called critical slowing down leading  to an increasingly slow recovery from perturbations. This, in turn, may lead to an increase in (spatial or temporal) autocorrelation and variance, while variance spectra tend to lower frequencies, and the 'direction of critical slowing down' in a system's state space may be indicative of a system's future state when delayed negative feedbacks leading to oscillatory or other complex dynamics are weak. Researchers have explored early-warning signals in lakes, climate dynamics, the Amazon rainforest, food webs, dry-land transitions and epilepsy attacks.