PDO turns positive: what does this mean for West Coast?

It's crazy how warm the Pacific is these days. Yet another story from the hard-working Chris Mooney at the Washington Post points to "the blob" of warmth in the Pacific off California.

Here's a map of sea surface temperature anomalies that gives an idea of that blob:


It's been extraordinarily warm in the Pacific, and in California, and that may not be a coincidence. Or so I hear. A scientist named Nate Mantua sees a connection with big implications for our future.

According to Mantua, the emergence of the new and consolidated “blob” may be a very significant development with global consequences. That’s because it may relate to a much larger pattern of ocean temperatures called the Pacific Decadal Oscillation, or PDO. A shift in this oscillation, in turn, may be a sign that the planet is on the verge of getting warmer, some scientists say.

Mooney writes:

Mantua also keeps an index of the PDO, and he says that at the moment, “my version has much more extreme positive values than theirs has.” But generally, the two indices are telling the same story, he says.

“In 2014 it went from mostly negative values to a very strong expression of the warm phase, and that’s present today,” Mantua says.

If the PDO is not only positive but is going to stay that way, it could be a big deal. Here’s why: Some scientists think a persistent cool phase of the PDO cycle may be a key part of the reason why there has been a much discussed “slowdown” of global surface warming recently. And if they’re right about that, then with the end of the cool phase, we may also see an end to any global warming “hiatus.”

Other scientists have linked the positive PDO to rainfall in Southern California, although an analysis by NOAA's Climate Diagnostics Center finds that statistically significant at only a marginal level.  


Correlation: .25

Significance: 5%

Variance Explained: 6%

The correlation of PDO to rainfall in Southern California is barely statistically significant at the 5% significance level. The correlation only accounts for 6% of the variance that occurs in annual rainfall.

High temperatures off the coast last year correlated to high temperatures here in California, and from what I hear, that's expected to continue. What else might we expect?

That is the question I hope to be able to ask Nate Mantua next week at a drought conference in Orange County.  

Published by Kit Stolz

I'm a freelance reporter and writer based in Ventura County.

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