The "Pacific Decadal Oscillation" (PDO) is a long-lived El Niño-like pattern of Pacific climate variability.
( It's very funny that the climate changes over the last 120 years fit somewhat closely with the pattern of the PDO. And man is creating the climate change??
Though the PDO cannot explain all the changes from year to year weather, it is but one of so many natural occurrences that are part of the big picture of global climate change that dwarfs any effect man-made greenhouse gases.
Brrrrr its cold today!)
Several independent studies find evidence for just two full PDO cycles in the past century: "cool" PDO regimes prevailed from 1890-1924 and again from 1947-1976, while "warm" PDO regimes dominated from 1925-1946 and from 1977 through (at least) the mid-1990's. Shoshiro Minobe has shown that 20th century PDO fluctuations were most energetic in two general periodicities, one from 15-to-25 years, and the other from 50-to-70 years.