Tuesday, October 7, 2014

Modeling: "In virtual mega-drought, California avoids defeat"

From the Los Angeles Times:
A few years ago a group of researchers used computer modeling to put California through a nightmare scenario: Seven decades of unrelenting mega-drought similar to those that dried out the state in past millennia.

"The results were surprising," said Jay Lund, one of the academics who conducted the study.

The California economy would not collapse. The state would not shrivel into a giant, abandoned dust bowl. Agriculture would shrink but by no means disappear.

Traumatic changes would occur as developed parts of the state shed an unsustainable gloss of green and dropped what many experts consider the profligate water ways of the 20th century. But overall, "California has a remarkable ability to weather extreme and prolonged droughts from an economic perspective," said Lund, director of the UC Davis Center for Watershed Sciences.

The state's system of capturing and moving water around is one of the most expansive and sophisticated in the world. But it is based on a falsehood.

"We built it on the assumption that the last 150 years is normal. Ha! Not normal at all," cautioned paleoclimate expert Scott Stine, a professor emeritus of geography and environmental science at Cal State East Bay.

"The weather record that we tend to depend on in California for allocating water … is based on about 150 years of really quite wet conditions when you look back at, say, the last 8,000 years or so," Stine said.
He found evidence of two extreme droughts in ancient tree stumps rooted in the state's modern lake beds. The trees could have grown only when shorelines beat a long retreat during medieval mega-droughts lasting a century or more.

Curious about how the nation's most populous state would fare under such chronically parched conditions, Stine, Lund and other researchers imposed a virtual, 72-year drought on modern California. In their computer simulation, annual runoff into rivers and reservoirs amounted to only about half the historical average. Most reservoirs never filled.

Under that scenario, experts say, irrigated farm acreage would plunge. Aquatic ecosystems would suffer, with some struggling salmon runs fading out of existence....MUCH MORE
Every scientist who is serious about this stuff makes the same "The weather since 1850 is not the norm for the region" point. So we try to pass it along:

"Crunch Time for California Drought"
As the headline for one of our September posts put it: "California: The Last 200 Years Were The Happy Time For Weather, Get Ready For A Return to The West Without Water" , recent history was the anomaly....
Straight Talk on Weather and Climate: "Will California's Drought Bring About $7 Broccoli?"
Two quick points:
1) The Great American Desert was called that for a reason. The weather of the U.S. over the last 150 years is an anomaly in the longer history.
2) The subsidization of row crops, corn in particular, is a political decision that severely distorts investment and thus nutrition outcomes....