Fig. 7.

Receiver Operator Characteristics (ROC) for the 15 early warning signals metrics. Where (a) a single signal over the threshold was considered a warning signal of recovery, and (b) when two consecutive signals were considered a warning signal of recovery across a range of threshold sigma values between 0.01 and 6. FPR = False Positive Ratio, TPR = True Positive Ratio. Points show the location on the curve corresponding to a 2-sigma threshold