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article imageTree rings: California's drought history is not a happy story

By Karen Graham     Dec 6, 2014 in Environment
Meteorologists were pleased with the heavy rains that pummeled California last week, but had to admit that it wasn't enough to improve the state's drought picture, calling the amount a "drop in the bucket." Actually, we have to get used to the drought.
Lakes and rivers are running dry, and crops are withering in the dusty ground. It's so bad that young salmon were given free transportation, with tankers trucks because the rivers were too low for them to make the swim to the ocean. This year alone, the drought will probably cost the state $2.2 billion, with 17,100 jobs lost and 428,000 acres of land left out of production.
The present drought's lack of precipitation is not that unusual if we look at tree-ring records, according to a study published Dec. 3 in the journal Geophysical Research Letters. Lead author Daniel Griffin, a tree-ring researcher at the University of Minnesota in Minneapolis says, "Precipitation is not the whole story for California drought."
Mono Lake in California on August 1  2014. Notice the dry lake bed. In 2013  the water depth was at ...
Mono Lake in California on August 1, 2014. Notice the dry lake bed. In 2013, the water depth was at about 50 feet.
Mary Phillips
Researchers are claiming the three-year drought being experienced in California is a perfect example of "consequential climate change." Griffin, along with paleoclimatologist Kevin J Anchukaitis are telling us the drought is the worst one the west coast has ever seen in at least 1,200 years. Their study shows that of the 66 prolonged droughts in the last millennium, the prolonged drought occurring now is the very worst. The researchers were also able to show that only three droughts similar to the present drought have occurred in the past 1,200 years.
Blue Oak tree rings tell a revealing story
The two scientists were driven by curiosity and were skeptical that the present drought could be the worst drought the state had ever seen. With some help from the Woods Hole Oceanographic Institute, they reconstructed California's precipitation and temperature history dating back to 800 AD using precipitation data and tree ring history.
A blue oak tree at the Blue Sky Ecological Reserve  Poway  San Diego County  California. It was blac...
A blue oak tree at the Blue Sky Ecological Reserve, Poway, San Diego County, California. It was blackened in a fire in 2008, but is still going strong.
Using tree ring samples from 278 blue oak trees, they were able to get a picture of drought conditions from hundreds of years ago. Blue oaks are extremely sensitive to rainfall and only grow in California. Their rings are wider during times of adequate precipitation and very close together during dry spells. Their analysis revealed that the summer of 2014 was the "worst single drought year in about 1,200 recorded years."
Patterns of narrow and wide tree rings correspond to dry and wet years.
Patterns of narrow and wide tree rings correspond to dry and wet years.
Daniel Griffin
Heat and a lack of precipitation make this drought different
What makes this drought so worrisome is the high temperatures that have gone along with the lack of rain. Griffin says that if we were talking about a drought with no rain, it wouldn't be very unusual because California has experienced many droughts, some lasting from three to nine years with little or no precipitation.
According to National Weather Service records, California experienced the hottest year on record in 2014. The high heat and low precipitation levels have been a double-whammy for the state. "Drought is going to continue to happen, and sometimes, it will be exceptionally severe," Griffin said. "This drought is a harbinger of what we can expect in the future."
To add to the gloomy forecast, in 2013, researchers at Cornell University revealed that the ongoing drought conditions in the Southwestern part of the country make it very likely to experience a mega-drought lasting 30 years or more.
More about california drought, worst in a millenium, Groundwater, Temperatures, lack of precipitation
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