The Pacific Decadal Oscillation (PDO) is a term coined by fisheries scientist Steven Hare in 1996. It describes recurring climate variability seen in the north Pacific that is similar to climate patterns resulting from El Niño/Southern Oscillation (ENSO) (Mantua, 2001).

The PDO has continent scale implications for air temperatures, precipitation, wind, oceanic circulation, nutrient transport, and even biological productivity (e.g. Mantua, 2001 and references within; Cayan, 1996; Bitz and Batisti, 1999; Chavez et al., 2003). Hare and Mantua (2000) claim that relative biological productivity of the oceans, which appears to be strongly influenced by climate oscillations like the PDO, may be a good predictor of short term climate change. Chavez et al. (2003) extend this statement by suggesting that relative abundances of sardines and anchovies in the Pacific Ocean can be used to predict climate regime shifts.

Gaining a deeper understanding of the PDO is necessary if we are to more fully understand global climate change as a result of anthropogenic sources and otherwise.