NO MORE WATER: Scientists, Oak Trees Predict Drought

After an unusually dry winter, experts in climate and weather are predicting drought for Ventura County and Southern California.
   
    Southern California experienced the driest fall and winter in over a century, according to the National Oceanographic and Atrmospheric Administration, and the drought is expected to continue and widen across the region.
    “The outlook for any significant drought improvement from now through spring looks grim for not only southern California but for much of the Southwest as well,” said Douglas LeComte, who forecasts drought for NOAA from his office in Maryland.
   
    Equally bleak but more colorful is Bill Patzert, who works at the Jet Propulsion Laboratory in Pasadena, and is known as "The Prophet of California Climate."
   
    "When in doubt," Patzert advises weather forecasters in Southern California, "vote for drought."
     Most alarming of all is the conclusion reached by NOAA researcher Martin Hoerling, who compiled climatological studies on the Southwest for the fourth  international scientific report on global warming, to be issued in full this year. Because drought is a measure of not only of rainfall but also of temperature and plant transpiration, and because temperatures are rising inexorably across the Southwest due to global warming, Hoerling in a paper (pdf) for Southwest Hydrology wrote that "a near perpetual state of drought will materialize in coming decades as a consequence of increasing temperature."

THE EXTREME MAKEOVER OF CALIFORNIA

    According to Henry Diaz, who has been researching meterological records in the West for NOAA since the l990s, temperatures in mountains across the Southwest have risen about two degrees Fahrenheit in the last 30 years. Snows in the high mountains are melting about two weeks earlier than in the past.  At lower elevations, such as in Ventura County, the temperature rise has been less, but Diaz says that the Southwest has been in a drought since l999.
   
    "We had a little bit of a reprieve in the last couple of years, which brought us closer to normal," he said from his office in Colorado, speaking of the heavy rains of 2005 and the near-normal rainfall of 2006. "You know precipitation is going to go up and down, week by week, month by month, year by year. But because of the warmer temperatures we have been observing in the Southwest over the last thirty years, we expect higher plant transpiration, with lower levels of soil moisture and recurring drought. This drought is consistent with that overall pattern of higher temperatures."
   
    Patzert looked at records from over 330 weather stations throughout California for the past thirty years for Climate Research and found temperatures had risen nearly two degrees Fahrenheit in the last thirty years, and much faster in urban areas, with Southern California rising fastest of all.
   
    "It’s definitely warmer in L.A.," he said. "Since May it’s been almost five degrees warmer Fahrenheit, versus a thirty-year historical average. We’ve had a lot of unusual Santa Ana conditions, and we’re now in an all-year fire season. I had one of my students look at extreme heat days, which means more than 90 degrees, and he found that we have on average 22 more extreme heating days than a hundred years ago. Our heat waves used to last three or four or five days. Now they can last two weeks. In the last one 180 people died. We’ve had less rain, more extreme heating days, and longer heat waves. I call it the Extreme Makeover of California."   
    Terry Schaeffer, a meterologist who has been advising Ventura County farmers on weather conditions since the l970s, hasn’t seen the same degree of heat change in Ventura County. But to explain the current drought conditions, he points to an oceanic trend called the Pacific Decadal Oscillation. This ocean trend can cause longer-lasting La Niña episodes (which usually bring drier winter conditions) and shorter El Niño episodes (which usually bring wetter winters).
    “The theory is that we’re going into a 25- to 40-year drought cycle,” he said. “Not every year will be a drought year, but the majority will.”

IS VENTURA COUNTY PREPARED?

    To citrus rancher Jim Coultas of Ojai, global warming means rising costs.
   
    "I’m in agriculture. I depend on a well and a hookup to Casitas reservoir, which costs about 10% more a year," he said. "As the level in the aquifer drops, you get less water out of the soil, and as the temperature goes up, you have to irrigate more. Absolutely that concerns me."
 
    Richard Handley, who serves on the board of the Casitas water district in Ojai, points out that from l910 to 2000, spring run-off from the Sierras decreased 10%. Since the Sierran snowpack supplies much of the state’s water, including about 40% of Ventura County’s needs, he thinks we will all have to make some changes.   
   
    "Global warming is only just now something that people are accepting as fact," he said. "It’s sort of like flying by night without radar."
   
    Handley is encouraged by some recent developments, including the removal of water-guzzling exotic species such as arundo dorax from streambeds. He points out that Ventura County survived a seven-year drought in the late 80’s and early 90’s with conservation measures.
   
    Russ Baggerly, also a water district official, thinks the time has come to rethink some of the conservation plans developed at that time.
 
    "Everybody works hard at dealing with water," he said. "The problem is that a lot of the thinking is out of the past and perpetuated into the future. We need to find a way to get a lot of different water companies to work together appropriately so that during a drought we don’t run out."

A DRY SUMMER–BUT NOT A HOT ONE?

    Although Patzert flatly predicts the hottest summer ever in Southern California, the next couple of months in Ventura will likely remain cool and foggy, thanks to the influence of the Pacific Ocean.
    "L.A. was drier than ever this year, and we were dry in Ventura County, too," said Kent Field, an air quality control meterologist for Ventura County. "But does that portend a long, hot summer? We could have low clouds and fog all summer, like "the summer that never was" we had here back in the l990’s."
        Schaeffer points out that "as the pendulum swings into a La Nina period, with cool ocean waters, that is likely to enhance our fog in May and June."
    
    But why should we listen to climatologists and meterologists? Aren’t these experts the same people who this past fall predicted an El Nino condition, with the likelyhood of significant rainfall?
   
    NOAA did predict an El Nino year this past fall, based on ocean observations, with an expectation of above-average rain and snow. Historically, for our coastal region, El Nino years average about 125% of precipitation.

    Yet not all NOAA employees–including Patzert and LeComte–had confidence in the consensus prediction. LeComte said he was "nervous" about the rainfall projections, because for his work as a drought forecaster he looks at a variety of forecasting tools, some based on soil moisture levels, and the soil moisture numbers were not corresponding with the predictions based on ocean studies.
 
   Patzert had a more personal reason to doubt the forecast. In his backyard he has an old oak tree, and for years he has noticed that the tree seemed to drop far more acorns before wet years than dry years.
     This past fall his tree produced virtually no acorns.
   
   Could an oak tree foresee a weather pattern that scientists couldn’t?

NATURE KNOWS THE SIGNS

    Patzert wasn’t the only Southern Californian to notice the lack of acorns this fall. Dave White, who worked for several years as a tree-trimmer in Ojai while becoming a science teacher, also noticed a connection between acorn drop in the fall and rain in the winter.
 
    "Two years ago it was uncanny," White said, "The trees produced a huge amount of acorns before we had those big rains. I asked my tree-trimming buddies about it, and they noticed the same thing. This year I could hardly find an acorn and so I thought, okay, we’re not going to get much rain."
   
    How could an oak tree predict rainfall? One possibility: a tree could sample the level of moisture in the soil over the course of a year and use that trend to guesstimate rainfall over the course of an upcoming season. Statisticians for NOAA and other forecasting agencies have been compiling historical measurements of soil moisture, called "constructed soil analogues," which match soil moisture records at given locations and time periods with rainfall and temperature records. The resulting outlooks are purely statistical, based on past experience, and available on the web. Although not yet approved for public use, LeComte says they are about as reliable as traditional methods for drought forecasts.
    "Forecasting skill is fairly modest for all our products," he said. "But when I’m forecasting, I give the statistical models about equal weight with the ocean models. I think their performance is pretty close, and I think in the future we’re going to need to work with more than one kind of forecasting tool."
   
     Patzert is blunter.
    "Well, my tree was certainly right this year," he said. "It was more prophetic than NOAA. 1500 civil servants could not compete with one hundred-year-old oak tree."

(This is the linked version of the story: for slightly edited unlinked version, see the Ventura County Reporter.)