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It may seem a little counterintuitive but it could very well happen due to global warming as the glaciers in Alaska and Canada continue to melt, dumping even more cold into the already chilly California Current headed south, while the melting of the ice caps down in Antarctica and Patagonia keeps adding more fuel to the icy Humboldt Current heading north up the South American coast and converging together at the equator and moving west and as the cold water spreads west it creates even more upwelling in the E. Pac., further compounding the La Nina and the long-term cold-phase PDO.

In contrast the colder climate of the pre-industrial the Arctic and Antarctic remained frozen all-year-round, reducing the input of cold water and weakening both the California and Humboldt Currents, and allowing for more big El Nino's and longer "warm" phase PDO's as well as pushing tropical waters from the western/central Pac. towards the eastern Pacific due to the westerlies being stronger and closer to the equator.

In reply to by Bob G