Forget El Niño: ‘PDO’ Could Flood California

While climatologists keep an eye on what could be an historic El Niño on the West Coast this winter, another, less-well-known weather pattern currently developing in the Pacific Ocean could end California’s drought and then some–leaving the Golden State up to its ears in rainfall for up to a decade.

Scientists are noticing a change in the “PDO,” or Pacific Decadal Oscillation, a climate index based on sea surface temperatures in the Pacific Ocean dating back to 1900.

Paul Chakalian at GlacierHub explains the nature of the PDO:

The PDO is primarily a sea surface temperature phenomenon that oscillates in the Pacific Ocean, usually switching from a warm or positive phase to a cool or negative phase every 20-30 years. In the positive phase the Eastern Pacific, along the West coast of the Americas is unusually warm, while the Western Pacific along the East coast of Asia is unusually cool. During the negative phase the opposite occurs.

The PDO is often described as a long lasting ENSO-like event. ENSO (El Niño Southern Oscillation) is what is commonly referred to as El Niño and La Niña, a sea surface temperature oscillation in the southern Pacific Ocean that is a strong predictor of precipitation anomalies, and therefore drought or flooding, around the globe.

According to Southern California Public Radio’s KPCC, scientists believe PDO could be entering its “warm phase,” which means water temperature along the Pacific coast heats up while the larger ocean cools down. When that happens, southern California and northern Mexico experience excessive rainfall, and the Pacific Northwest becomes dry.

Bill Patzert, a climate scientist at Pasadena’s Jet Propulsion Laboratory, says that the PDO has likely been in a “cool phase” since 1998, which has helped contribute to the state’s current record drought.

And with the likelihood that even a “super El Niño” wouldn’t pull the Golden State out of drought, Patzert says it is more critical than ever that the PDO continue to switch to the warm phase. Patzert said the data indicating the switch has already been present for the past 19 months.

“Perhaps in the long term, rooting for a [warm] PDO…is probably the most important thing for California and the American West,” Patzert told SCPR. “In the long run, these decadal or multi-decade variations in the Pacific are really the key to sustaining California agriculture and California civilization.”

In the meantime, California will look to conserve as much water as possible until the rain comes. So far, the state is on track to meet or even exceed Gov. Jerry Brown’s order for a mandatory 25 percent cutback in water usage statewide.