The PDO (Pacific Decadal Oscillation) describes SST variations in the North Pacific on 20–30-year timescales. In positive phase, the central Pacific is warmer and North American coasts cooler; in negative phase, the reverse.
Global impact
The PDO modulates the frequency and intensity of El Niño/La Niña: in positive phase, El Niño events are more frequent and intense. It affects Pacific fisheries (salmon, sardine), North American precipitation, and Asian monsoon intensity. Being decadal in scale, it cannot be predicted like ENSO.