Scientists Warn State to Get Ready for Drought

Southern California water managers should start preparing now for the unruly effects of future climate change, a panel of scientific experts warned Tuesday.

The consequences range from possible decades of drought to diminishing levels of the Sierra snowpack, which replenishes state water supplies each spring.

“I think there will be some serious negative impacts from climate change on our state,” said Peter Gleick, a climate expert who directs the Pacific Institute for Studies in Development, Environment and Security in Oakland.

Gleick and three other scientists were invited to address the Metropolitan Water District, the region’s biggest water wholesaler, after board members became concerned about recent climate forecasts predicting a future of consistently hotter and drier weather.

A looming concern is whether California is headed into a long-term drought. William Patzert, an oceanographer with NASA’s Jet Propulsion Laboratory, said that a large-scale change in ocean temperatures called a Pacific decadal oscillation, or PDO, now appears to be shifting into a “cool phase” that could bring decades of drought to the region.

The Pacific decadal oscillation, which Patzert calls “the mother of El Nino,” is, like El Nino, a shift in ocean temperature that can affect weather and rainfall on land. It involves a much larger swath of the ocean than an El Nino or El Nino’s opposite, La Nina, and has farther-reaching and longer-term effects.

There is much debate in the scientific community over whether the Pacific has shifted into a cool phase or whether any drought is imminent. Many scientists say it is too early to make such a prediction.

But Patzert predicts the current ocean temperature system could lead to 30% less rain for the next two or three decades in Southern California.

“I’ll stick my neck out and say there is a fair possibility” of drought, he said. This year’s rainfall total for Los Angeles, measured from July to July, is expected to fall below 12 inches, three inches less than normal, he noted.

Changes in ocean temperatures, such as the decadal oscillation and El Nino, are natural cycles that predate the influence of humans. But human-induced climate change, such as global warming, may also increase the possibility of drought by altering the snowpack, Gleick said.

In warmer winters, an increasing amount of California precipitation would fall as rain, rather than snow, he said. Snow is preferred by water managers as well as skiers because it is less likely to contribute to winter flooding and stays in the mountains as snowpack until it melts, conveniently, when it is most needed: late spring.

Warming could mean less snow, and snow that melts earlier and faster so it cannot be efficiently captured and stored in the existing storage system. “This is the opposite of what we want,” Gleick said.

California is no stranger to extended periods of drought, experts on past climate said Tuesday. By looking at tree rings in conifers that live for 700 to 1,500 years, scientists have pieced together records of precipitation reaching back to AD 656.

“Is there anything in here that should frighten us?” asked Glen MacDonald, an expert on past climate with UCLA’s Institute of the Environment, as he showed water board members the record. “Yes, there is.”

He pointed to a period in the late 16th century when there was drought, not only in Southern California, but also throughout the Southwest. This included areas that feed the Colorado River, which supplies more than half of the district’s water.

Droughts are a “persistent and natural part of our environment,” he said. “They will occur in the future.”

Jeanine Jones, an engineer with the California Department of Water Resources, said droughts of the past have been far more severe than anything seen in recorded times. But predicting future droughts is nearly impossible, she said.

In addition, predicting the effects of climate change for the state is difficult because California stretches across different climate zones. While a La Nina event might mean a drier winter for Southern California and more rain for the Pacific Northwest, it is not clear how such ocean patterns affect Northern California or the Central Valley, she said.

Because Southern California gets its water from the Owens Valley, Northern California and the Colorado River, local water supply would not be seriously affected unless there was drought in several areas, she said.

Still, the scientists said it was important for water managers to begin planning for changes that are increasingly seen as inevitable.

“I feel very challenged,” board member Helen Z. Hansen said after the presentations. Climate change is “something we must be prepared to deal with.”

Board member Timothy F. Brick said the district board members must be sure “we are hedging our bets for the future.”

As it grapples with decreasing the district’s reliance on Colorado River water and with slaking the thirst of a booming state population, he said, the board should also plan upgrades of water storage systems, improvements in conservation and consideration of techniques like desalination. The board did not discuss setting water limits or raising rates.

“For some people, thinking about climate change may be an intellectual exercise,” said Adan Ortega, the water district official who organized Tuesday’s event. “For those of us in the water resource management business, it is an essential fact of daily life.”