El Niño 2010: small, medium, large ... or wanna-be?

Local forecasters make their predictions for the year

By Kit Stolz 01/14/2010

In 1975, Bill Patzert was a graduate student at the University of Hawaii in oceanography, assigned to go out on a ship called the Moana Wave and document sea surface temperatures and wind speeds in the Pacific Ocean, to prove or disprove the latest idea in climate science.

“It was the first time anyone thought an El Niño could be predicted,” Patzert recalled. “I was the junior member on a team of research scientists, but the chief scientist on board the ship. We were convinced we were seeing the signs of an El Niño forming, with a relaxation of the trade winds blowing eastward, and a warm pool forming off Ecuador, but like so many of these events it was short-lived. The experts predict an El Niño every three or five years or so, but the real ones, the ones that’ll make you pee in your Pampers, they only come about every 12 or 15 years.”

Rainfall totals in Southern California bear out Patzert’s observation. El Niño, the best-known and most powerful of all ocean climate patterns, in its warm (positive) phase brings a flow of warm water from the tropics along the equator toward the west coast, in what’s called a Kelvin wave, about every five years, which feeds moisture to rain patterns in our area. But the last El Niño episode, in 2003, brought only slightly more rainfall than normal to our area, and has already been forgotten, while the huge storms of 2005, which devastated the state and killed 20 people, had little or no connection to El Niño.

Those devastating rains came to us thanks to the so-called “Pineapple Express,” which brought rain directly from the tropics, over Hawaii and onto Southern California, encouraged by another seasonal ocean pattern called the Madden-Julian oscillation. The Madden-Julian oscillation appears to have moved the ridge of high pressure that often forms over California eastward and north in the Pacific in late December 2004 and early January 2005, according to the national Climate Prediction Center, allowing tropical storms to hit Southern California head on.

The last El Niño to bring major rainfall to Ventura County came in l997-l998, and it was a doozy, still the wettest year on record, according to the VC Watershed Protection District, with about 39 inches of rain in Ventura and about 50 inches of rain in Ojai.

If you ask Ed Olenic, who predicts seasonal weather for the National Oceanic and Atmospheric Administration, how this year’s El Niño rates on a historical scale, he will say it’s fairly strong. The strongest El Niño on record, the l997-98 model, notched at 2.5 on the Oceanic Niño Index, while this year’s model comes in at a 1.8, he said, the same mark reached by the El Niño of l991-92.

But if you look at rainfall records, you will see that rainfall in the l991-92 water year was only slightly elevated, by about five inches in downtown Ventura, compared to an additional downpouring of 25 inches of rain in the epochal water year l997-98.

El Niño: Size does make a difference
“El Niños come in small, medium, large and Godzilla,” Patzert said. “The last Godzilla El Niño we had was in l998, and the one before that was in l983. The others are mostly wanna-bes. But the ’97-’98 El Niño triggered something deep in the cortex of reporters, and now whenever the word is mentioned, they start salivating.”

Terry Schaeffer, who has been predicting weather for the agricultural community in Ventura County since the l970s, seconds this observation.

“I agree 100 percent,” he said. “Just because it’s a heavy rain year doesn’t mean it’s an El Niño, and although a strong El Niño can bring good rain, the light to moderate El Niños are much harder to predict. We are in an El Niño pattern now, with mild winter temperatures, but I don’t see a likelihood of any rain soon. I think we’ll see a pattern change later in the month, which could open the door to some storms, but whether they will be there to come through the door, we don’t know. I’m still guardedly optimistic that we’ll have a normal year for precipitation, plus about 15 percent, but I suspect that overall we’ll still be in a drought.”

By contrast, the official forecasters for seasonal weather prediction in the U.S., the Climate Prediction Center in Maryland, an offshoot of the National Oceanographic and Atmospheric Administration, continue to call for heavier-than-average rainfall totals across most of the southwestern U.S, thanks to El Niño.

“We have an El Niño that has reached strong status,” said forecaster Ed Olenic. “Of course, we’re just in the middle of the season, and the full impact of El Niño isn’t usually felt until mid-January.”

What national El Niño forecasters don’t see
Patzert, who works for the NASA-affiliated Jet Propulsion Lab in Pasadena, has been looking intently at the ocean patterns of El Niño, which tends to bring winter mildness and rain to the West Coast, and its mirror image La Niña, which tends to bring dryness and cold, from space since l992. That’s when NASA and a French space agency launched a satellite called TOPEX.

Topex and its satellite successors JASON 1 and 2 can precisely calculate ocean sea levels across vast distances to a millimeter scale, and with this data scientists are able to map ocean heat flows as never before. Where NOAA forecasters rely mostly on data from buoys, Patzert looks at satellite data that allow him to see temperature changes (caused by the expansion of sea water in the “mix layer”) farther below the surface.

But he doesn’t look just at the seasonal patterns, such as El Niño.

“I was heavily addicted to TOPEX data, and now I’m heavily addicted to JASON data, and what the data shows is much more than El Niño,” he said. “We also see the Pacific decadal oscillation.”

The Pacific decadal oscillation, or PDO, is a difficult concept to visualize, because it’s hard to imagine the biggest thing in the world as a bathtub, with warm water sloshing back and forth in flows the size of continents. But that is the Pacific Ocean as ruled by the Pacific decadal oscillation.

First identified in l996 by researchers at the University of Washington, the watery “fingerprints” of the PDO now have been traced by scientists back millennia, even though it’s invisible to the eye, and works its influence over 20 or 30 years at a stretch. In the PDO’s negative (cool) phase, the ocean waters off the West Coast are cooled by as much as ten degrees Fahrenheit, while eastern Pacific off Japan and northwards warms about equally. Currently the PDO is negative, but barely so.

In its negative phase, which is what we is happening now, the waters off California and much of the central Pacific are slightly cooler, and the waters off Japan and Siberia, warmer.

“Think of the PDO as a large La Niña that El Niño is trying to overcome,” Patzert said. “That’s why my prediction for rainfall this year is low. We saw a wetter than normal fall, but I think we’ll see a dry January, a wet February, and then it’ll fizzle out.”

As a forecaster, Patzert has a long history of crossing swords with the NOAA forecasters and being proven right.
In the summer of 2002, the national forecasters predicted the return of El Niño and a wet winter. Coming after the disastrously strong El Niño of l997-l998, that prediction made headlines.

Patzert scoffed.

In the ensuing winter, rainfall levels were barely above normal.

In July 2006, NOAA forecasters predicted a global El Niño, with a warm, rainy winter for Southern California.

Patzert predicted a dry winter, and was again proven right.

What does Patzert see that the forecasters at NOAA don’t?

“The PDO,” he said. “They don’t look at it.”

Olenic at the Climate Prediction Center — the agency that makes the official seasonal El Niño forecast for NOAA — disagrees.

“Well, of course, we look at the PDO,” he said. “We know about it, and we measure it. But we have a great deal of difficulty in finding strong impacts on a seasonal scale, when the PDO takes place over 10 years or more. It may be that the PDO has some influence that we don’t yet understand, but for the time being, it’s difficult to use in forecasting.”

The negative PDO: a drought predictor?
Terry Schaeffer, of Weather by Schaeffer, points out that the last decade in which the Pacific decadal oscillation (PDO) was in a strongly negative period, the l950s, also turned out to be dry.

“We’re in the midst of a long-term drought, the same as we were in the l950s,” he said. “Overall, the decade was very dry, but we still had a couple of wet years in the l950s, and a couple years that were close to normal. I think we’re going into a long-term drought, and it’ll probably be dry for 20 or 25 years, as long as the PDO is in its negative phase.”

Patzert agrees, and points to California’s climate history as a reason for concern, saying that the droughts California and the Southwest have experienced in recent years, including the Dust Bowl, were minor compared to the “megadroughts” of past millennia.

Archaeologist and historian Brian Fagan, who last year published a book called The Great Warming about the warming experienced in California and around the world in the Middle Ages, offers the past as a troubling prologue.

“People don’t realize that the past 700 years in California have been unusually wet,” he said, on the phone from his home in Santa Barbara. “The lesson of history is that as temperatures rise, droughts become more prevalent.”

In his book, Fagan documents droughts in California in that warm period of climate history that lasted for decades at a stretch. One began in 1210 and lasted until about 1350, which, according to geographer Scott Stine, reduced runoff from the Sierra snowpack to about 45 percent of what it is today.

“I really think that we ignore the possibility of long-term droughts at our peril,” Fagan said. “Even California natives such as the Chumash, who were well-accustomed to these kind of arid and semi-arid conditions, saw substantial change and struggle. For one thing, their leaders became much more rigid about policing territory and controlling trade, which brings the danger of violence. One of the things that strikes me about our future is that we’re going to have to develop a more authoritarian approach to the way we handle water. Why? Because other mechanisms may not work.”

While Fagan is documenting past warming, due to natural variability, paleoclimatologist Michael Mann and a team of scientists based at Penn State published in November a study in Science suggesting that as the planet warms, the PDO may strengthen and increase our chances of dry, cold La Niña winters and decrease our chances for warm, wet El Niño winters.

“The last time there was a relatively positive radiative imbalance in the climate system during medieval times, due to high solar output and fewer volcanic eruptions, the climate was more La Niña-like, and the desert Southwest was dry,” he said in an e-mail answer to a question. “So if we consider that era as an analogue for the modern positive radiative imbalance (which this time is not natural, but instead due to increasing greenhouse gas concentrations associated with human activity) then it could portend increasing southwestern U.S. drought.”

Not all mathematical climate models agree with this scenario, but veteran local forecaster Schaeffer has been telling his grower clients to expect dryness and drought for the next 20 or so years, as long as the PDO is in its negative phase.

How do the growers react, when he tells them this?

“They generally run out of the room screaming,” he said with a chuckle. Schaeffer went on to explain that farmers in Ventura County have always had to adapt to changes, and what they grew 40 or 50 years ago is not what they often grow now, and what they grow now will likely change over time as well.

But he didn’t take back his prediction for a 20- or 25-year drought.

For more information about Kit Stolz, go to www.achangeinthewind.com.

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