Early-Warning Signals for Critical Temperature Transitions

Critical transitions of the state variable (temperature) in dynamic climate systems often lead to catastrophic consequence, whereas the effort to reverse the transitions usually lags behind. However, these transitions are characterized by the slowing down of recovery from perturbations, carrying early-warning signals that can be used to predict system bifurcation. In this study, we employ the conceptual framework of pitchfork bifurcation and analyze the early-warning signals in temperature time series for critical slowing down prior to both the early 20th century global warming and heat waves. We also investigate the urban signature in these heat waves. The emergence of early-warning signals before heat waves provides new insights into the underlying mechanisms (e.g., possible feedback via land-atmosphere interactions). In particular, given the increasing frequency and intensity of heat extremes, the results will facilitate the design of countermeasures to reserve the tipping and restore the resilience of climate systems.