Detecting early warning signal of the Pacific Decadal Oscillation phase transition using complex network analysis

<p><span>Obtaining an efficient prediction of the Pacific Decadal Oscillation (PDO) phase transition </span><span>is a worldwide challenge. Here, we employed the climate network analysis to uncover early </span><span>warning signals prior to a PDO phase transition. This way an examination of cooperative </span><span>behavior in the PDO region revealed an enhanced signal that propagated from the western </span><span>Pacific to the northwest coast of North America. The detection of this signal corresponds </span><span>very well to the time when the upper ocean heat content in the off-equatorial northwestern </span><span>tropical Pacific reaches a threshold, in which case a PDO phase transition may be expected </span><span>with the arising of the next El Niño/La Niña event. The objectively detected early warning </span><span>signal successfully forewarned all the six PDO phase transitions from the 1890s to 2000s, and </span><span>also underpinned the possible PDO phase transition around 2015, which may be triggered </span><span>by the strong El Niño event in 2015-2016.</span></p>