Pacific Decadal Oscillation: Climate Trends

The following table shows how air temperatures, precipitation, and related effects in North America have been correlated with with extreme PDO anomalies.

Climate Anomalies	Warm Phase PDO	Cool Phase PDO
Ocean surface temperatures in the northeastern and tropical Pacific	Above average	Below average
October-March northwestern North American air temperatures	Above average	Below average
October-March southeastern U.S. air temperatures	Below average	Above average
October-March southern U.S./northern Mexico precipitation	Above average	Below average
October-March northwestern North America and Great Lakes precipitation	Below average	Above average
Northwestern North America springtime snowpack	Below average	Above average
Winter and springtime flood risk in the Pacific Northwest	Below average	Above average

Source: adapted from Mantua, 2001

In the following figure, the PDO has been correlated with (A) global air temperatures (after removing the global warming signal), (C) atmospheric circulation in the Pacific Ocean (zonal or meridional atmospheric transport), (D) atmospheric carbon dioxide levels with anthropogenic increase removed, (E) a "Regime Indicator Series", which is a measurement of anchovy and sardine populations throughout the Pacific Ocean, and (F) the"Southeastern Pacific Ecosystem Index", a measurement of anchovy, sardine, and seabird abundances in Peru (Chavez et al., 2003). Since the mechanisms controlling the PDO remain unknown (Mantua, 2001), it is unclear if the PDO is forcing these changes in atmospheric conditions and biological ecosystems, or if the PDO is a result of the changes in atmospheric conditions.

Source: adapted from Chavez et al., 2003