It's a big question. Talk to anyone who works on the land in Southern California and you'll hear discussion of El Niño, rain, winter, drought, scientists who can't agree– and so on.
I set out to get to the bottom of it last month for the Ventura County Reporter, and (dare I say) succeeded as well as could be reasonably hoped. Not that the comments on the piece reflected that: any mention of cllimate change brings out the cranks, I guess. from the chemtrail people to the climate change deniers.
But the real news is that in the short-term, the consensus looks decent. We will have rain this winter, scientists agree.
What's troubling for SoCal is the long-term prediction — increased dryness. Yikes.
Here's the start: I'll put the kicker below the fold.
"The last 12 months (from September 2013 to September 2014) have been hotter than any other 12 months in the 113 years that reliable temperature records have been kept in California, according to the National Oceanographic and Atmospheric Administration.
The last three “water years” have also been the driest such period in the state’s history, NOAA says. The term U.S. geological Survey “water year” in reports that deal with surface-water supply is defined as the 12 month period for any given year through September 30 of the following year. As a result the entire state is in drought, and Ventura County — like all of the central coast of the state — is in category 5, or “exceptional drought,” the worst of all possibilities.
[here's an image drawn from data collected by the pair of satellites known as GRACE, which shows how California is drying out as the level of available water below ground sinks]
In Ventura County, we experienced drought — rainfall totaled only about six inches at the harbor, considerably less than half the average — this year and we also missed the cooling fogs that usually come in off the ocean in the early summer months. The “May Grays” and “June Glooms” that customarily haunt the shore and hold down temperatures as the summer begins to warm made only a brief appearance.
Meanwhile, the ocean waters off our coast have been hotter than normal this year, by about 3 to 7 degrees. Mike Thompson of Channel Islands Sportsfishing said that species not seen here in a decade’s time, such as yellow fin tuna, have been caught recently off the coast. In August, small jellyfish with translucent sails, known as by-the-wind sailors, which usually are found out at sea, showed up in large numbers on our beaches. Market squid, which most years are harvested by the ton out of Southern California harbors, have been sparse in our unusually warm waters this year but abundant in the cooler, nutrient-rich waters off the North Coast.
Were all these unusual events coincidental?
Not really, according to Bill Patzert, who, from his perch at Jet Propulsion Lab in Pasadena looks at down at the ocean from satellite records and delivers forecasts with the confidence of a man who has seen the patterns develop for decades. The same winds and warmth in our waters that brought us rarely seen sea life also reduced the temperature differential between the Pacific (which usually is much cooler than the land in summer) and the land (which usually warms more quickly than the ocean).
This meant less fog along the coast — and more heat inland.
But where did these unusually warm ocean waters off our coast come from?
The Jason-2 satellite records that Patzert’s team compiles for NASA show that the unusual warmth off our coastline can be traced back to a far greater warming in the ocean waters in the western Pacific. For reasons still not fully understood, this vast area near Indonesia — known by experts as the “warm pool” — will every few years overflow and generate what scientists call Kelvin waves.
Over the course of a couple of months, moving across the wide belt of the equatorial Pacific, only slightly raising the surface of the water, these waves — the size of small continents — slowly transport vast amounts of heat energy under the surface across the ocean. With satellite data, the warmth can be seen moving along the equator, hitting Central America and then splitting and propagating along the coasts, eventually reaching us in Ventura.
The change in the temperature of the Pacific alters water temperatures and the air above; and, in time, trade winds that customarily blow from west to east can ease, or even reverse, and blow from east to west, toward California.
These wind patterns enhance our chances of getting winter storms and rain.
“Earlier this year in January and February we saw that relaxation in the trade winds, along with Kelvin waves in February and March and April, and then this high sea band began to develop,” Patzert said. “Everybody said it was beginning to look like l997-l998 [when the biggest El Niño ever recorded hit, breaking records around the world].”
Back in the fall of l997, after seeing this sort of Kelvin waves come across the Pacific without pause for months, Patzert forecast rains twice the amount of normal for Southern California. (Ultimately, according to the National Weather Service, after a dry December rains came in force in l998, ultimately totaling 298 percent of normal in the county.)
As Kelvin waves warm the equatorial Pacific, they drive a complex cycle of winds and currents that can lead — although not invariably — to an El Niño condition, which in turn can lead — although not invariably — to heavy rain in California. Hence the excitement among forecasters earlier this year. The national Climate Prediction Center bumped its monthly estimation of the likelihood of an El Niño to 80 percent in July, and experts speculated about how strong and rainy it might be.
Patzert himself, who has been in the El Niño business since the phenomenon began to be charted in the late 1970s, and who throws words and metaphors at the press the way Mike Hammer used to throw punches at bad guys, allowed himself an unusual moment of hope for an upcoming El Niño.
“Don’t hyperventilate yet,” he told a reporter for the San Jose Mercury News in early April. “It’s a little too soon to say the drought is over, but this Kelvin wave is no dud. This is a stud.”
Why an El Niño may not save us from drought
Kelvin waves start the cycle that can lead to El Niño, but in the same way that hurricanes require ocean waters to be a certain temperature before they will begin to form, so too does the equatorial Pacific need to reach a certain temperature — about one degree Celsius above normal — before forecasters have any confidence that the cycle will bring rain to California. After seeing a huge Kelvin wave form in early spring, forecasters expected to see more warmth moving across the ocean, but were mostly disappointed. The mid-Pacific warmed, but only slightly — it’s about half a degree above normal in October. Although forecasters still peg our chances at an El Niño this year at 66 percent, they say it will be weak, and stress that it’s not at all clear this will mean good rain in California this winter.
“Weak to moderate El Niños are not necessarily rainmakers,” Patzert said. “So instead of the great wet hope my forecast is for a dry disappointment.”
After being repeatedly let down by El Niño, Patzert has become a bit cynical about it. He keeps pointing out that the phenomenon can be detected in the ocean far more often than it brings rain to Southern California.
In 2012 a moderate El Niño formed, but only 11 inches of rain fell in the county. The Ventura County Watershed Protection District called it “a very dry year.”
In the fall of 2006, after a heavy rain year in 2005, a moderate El Niño began to form, and NOAA forecasters warned of the possibility of substantial rainfall for the region that water year. At a meeting of the American Meteorological Society, Patzert scoffed out loud about the prediction, calling it “El Wimpo” in front of the press. This did not endear him to his forecasting peers, but when the 2006-2007 rainfall in Southern California turned out to be the driest in the historical record they started calling him “the prophet.”
Looking back, Patzert shrugs off the description.
“It’s heavy, man,” he said, speaking in the dryly sarcastic voice of a man who frankly admits that he too has gotten forecasts wrong over the years.
“Yeah, I’m a prophet, like Isaiah or John the Baptist. Look what happened to him.”
Nonetheless, Patzert’s doubts about El Niño as a savior this year are echoed by many other forecasters and scientists. Even if we receive better than average rains, we still will be dependent on groundwater supplies that have been substantially drawn down by three years of drought. Only the wettest of El Niños could bring water back to us in abundance. Research hydrologist Mike Dettinger at the Scripps Institution of Oceanography estimated that our chances of being fully replenished by heavy rains this year were just 15 percent.
More alarmingly, a team of climatologists at Stanford, led by Daniel Swain, in September published a paper in which they argued that our drought is man-made — caused by a ridge of high pressure in the atmosphere in the North Pacific that they link to climate change.
Pointing the finger at drought: the RRR or the PDO?
The North Pacific High is nothing new to meteorologists. It’s a ridge of high pressure in the atmosphere, comparable to a mountain ridge. It comes in all shapes and sizes, reaching as high as 30,000 feet, and often forms off the coast of the Northwest. But Swain gave it a new name — and new fame — because he identified it as the culprit in our drought as it persisted off the coast north of the Canadian border.
Low pressure systems that bring clouds and possibly rain or snow to California and the West are often blocked by the North Pacific High. Swain compares it to a boulder in a stream, forcing storms to go around it. In October a team of scientists led by Ben Cook at NASA found that this same blocking ridge led to the drought in California in 1976-l977, and also the Dust Bowl in 1934 that devastated the farms of the High Plains.
In the normal course of events, the North Pacific High will form and dissipate countless times in the course of a winter. But in December 2013, after a year of drought, and after seeing this ridge form and reform and strengthen virtually without cease, diverting storms headed our way, even those as far north as the Arctic, Swain gave it a new name: the Ridiculously Resilient Ridge, or “RRR.”
“I wanted a term that would accurately refer to the ridging feature, and that would describe its evolution over time, with resilience referring to the way it would pop right back up every time a storm came along,” he said. “I also wanted to highlight how unusual this persistent ridging had become, so in a moment of spontaneous alliteration I chose ridiculous.’ ”
By statistical means, Swain and his colleagues looked at how likely this persistent ridging would be in a climate that had not been altered by the introduction of additional carbon dioxide from the burning of fossil fuels. (Since 1880, when about 280 parts per million of carbon dioxide were present in the atmosphere, the burning of billions upon billions of tons of coal, oil and gas has raised the proportion to about 400 parts per million today.) Swain and his team found that the Ridiculously Resilient Ridge was three times as likely to form and persist today as it would have been before the burning of fossil fuels.
The Obama administration reached a similar conclusion, although probably not from an analysis of “geopotential heights” of meteorological formations. In late January, according to reporting from the Washington Post, after looking at NASA pictures of the Sierras barely dusted by a snowpack on which California depends for the bulk of its water supplies, the administration was galvanized into action on climate change.
President Obama went on to announce a range of initiatives, from EPA restrictions on emissions from power plants to heightened expectations for mileage from car manufacturers and support for climate change treaties. In California, legislators and Gov. Jerry Brown quickly assembled a water bill package totaling about $700 million to conserve water in both dams and underground basins and, later in the summer, for the first time instituted the beginning of a state regulation of local groundwater.
But do we really know for certain that climate change caused the drought in California?
Did climate change cause our recent drought?
Although Swain’s study linking the California drought to climate change has been widely reported, it was one of three studies on the question in a special bulletin of the American Meteorological Society in September. The other two studies were not so sure of the causation. One, by Hailan Wang and Siegfried Schubert, looked at the extreme dryness of the winter of 2013 and agreed that a persistent ridge of high pressure in the northern Pacific due to long-term warming blocked storms that would otherwise have reached California, but also found increased humidity over the northeast Pacific, and argued that the two climate effects would cancel each other out over the long term. A third study, led by Chris Funk, did not find that an increase in warming in the climate models led to a decrease in precipitation (rain and snow).
On the same question of rain, a study published in August in the journal Climate found that California has not seen a change in the total amount of annual rainfall, despite registering a warming of about 1.7 degrees Fahrenheit in recent decades. (By contrast, in a recent period, warming led to an increase in precipitation in the nation as a whole by about 10 percent, according to one study.) In the Climate study, alarmingly, Steve LaDochy, a professor in the Department of Geography and Urban Analysis at Cal State L.A., and his colleagues did find a trend toward “a large decrease” in rainfall in Southern California since the l970s, totaling 27 percent.
But given that the State Water Project already transports water from the Trinity River and other sources in Northern California to a drier Southern California, LaDochy argues these changes could cancel each other out for Southern California.
“More than one study has shown that the shift in climate and the storm track doesn’t favor us very much, but it may make northern parts of the state wetter,” he said. “And if you look at the paleoclimate record, California has had megadroughts that lasted for several centuries.”
With many other researchers, including Patzert, LaDochy thinks that another ocean temperature pattern, called the Pacific Decadal Oscillation (PDO), discourages or encourages rainfall in California and the West. Like El Niño and La Niña, only far bigger and far longer lasting, the PDO brings cooler or warmer temperatures to the ocean up and down the West Coast. Since the last huge El Niño of 1997-l998, the eastern Pacific has been in a “negative,” or cool phase, which historically has been associated with dryness in Southern California.
To Terry Schaeffer, who has been forecasting weather in Ventura County on a subscription basis for farmers for over 40 years, the PDO probably explains the drought of recent years better than anything else. He points out that California suffered through long droughts before, such as the mid-20th century drought that motivated farmers in Ojai to back the construction of Lake Casitas. And he points out that these dry periods, when the PDO is negative, tend to last longer than the wet periods, when the PDO is in its positive, or warm ocean, phase.
“Our wet spells tend to last 20-25 years,” he said, noting that the 1980s and 1990s were a very wet period in the historical record. “But our dry spells tend to last 35-40 years. That doesn’t mean that you can’t have a wet year or two in that span. But I don’t see our long-term drought ending soon.”
Nonetheless Schaeffer forecasts a mild winter for the county, with above-normal rainfall, probably beginning later than usual in the year.
Mike Halpert, deputy director of NOAA Climate Prediction Center, agreed.
“I would be stunned to see a repeat of last winter,” he said. “I expect what the statisticians call “a regress to the mean” — a return to normal. There’s a reason we call it an average.”
Patzert also agreed.
“Hang in there,” he said, to this reporter and to all of Southern California. “We will get rain — eventually.'"