Extreme weather threatens Calif. on several fronts

Anne C. Mulkern, E&E reporter
Published: Thursday, December 15, 2011

Powerful storms, droughts and other extreme events threaten California's water supplies, crops and people and the risks will worsen over the next century, scientists said.

At a Tuesday conference in La Jolla tied to Gov. Jerry Brown's (D) event today on climate change and extreme events, researchers in several fields detailed what is known so far about the impact of higher temperatures and what changes are needed to prepare (ClimateWire, Dec. 12).

The forecasts were largely pessimistic. Extreme events like extended droughts in California are expected to increase in frequency and intensity, scientists said.

"It's a huge concern for the public health sector, for agriculture, for ranching, for the energy sector," said Alexander Gershunov, climate researcher at Scripps Institution of Oceanography. "It's a huge concern for the California economy."

Extreme climate events will have an effect on the coastal regions as storms interact with higher sea levels, scientists said. Rising oceans and heavy rainfall could overrun the delta in Central California, potentially reducing flows of water to southern parts of the state from the north.

And in some situations, the climate change-driven extreme events have the ability to affects other parts of the county.

The state's agricultural bounty -- with popular crops like cherries, apricots, lettuce and grapes -- already is being affected by heat waves and droughts. In 2006, production of red and white wine grapes fell sharply during a period when there had been high nighttime heat, said Gershunov, who researched the
correlation between the events.

"Winemaking is a huge industry in California, so I'm sure the impact was very large," Gershunov said.

The scientists talked about research that already has been done, as well as where information gaps exist. Several touched on the need for more studies into ways of adapting to more frequent and intense
weather events in the future.

Uncertain weather becomes a given

The agricultural industry could look at increasing its diversity of crops, said Louise Jackson, a professor in the Land, Air and Water Resources Department at the University of California, Davis. The state might also want to look at farming crops that can thrive even when water is limited, she said.

Pistachios and olives both are high-value, and "they produce well even under a low water supply," Jackson said. Rice and alfalfa, also grown in the state, require more water, she said.

The state, which produces more than 300 crops, has many climates and microclimates, Jackson said, so one of the challenges could be figuring out how to change farming locations. Cherries and apricots require need cool nighttime temperatures "to flower and fruit well," she said.

"That could be a problem in warmer winters," Jackson said.

But one of the challenges is that it's unclear how much future extreme events could damage crops, she said.

"One of the main things that we have to deal with is uncertainty," Jackson said. "Planning for uncertainty is quite difficult. We don't know the extent and potential of heat waves, droughts.

"It means that we have to take a different strategy towards our agriculture research," Jackson added. Contingency plans are needed for the long term, she said.

Less water, more powerful storms

Pinched water supplies could affect much of the state.

Models show that the amount of snowpack in the Sierra Nevada region is in "a pretty big downward trend," said Marty Ralph, chief of the water cycle branch at National Oceanic and Atmospheric Administration (NOAA).

"This will have a profound impact on water supply for California," Ralph said.

Projections for the Colorado River Basin are also negative, estimating a 5 to 20 percent decline in runoff over the next century, Ralph said. That would affect water supplies for Arizona, Colorado, California, Utah and Wyoming, he said. While droughts are expected to increase, there is also the possibility for more storms with heavy rainfall. One study suggested that back-to-back storms could dump as much as 40 inches of rain in California over a few days, Ralph said, causing damages that would top $500 billion statewide.

"The impacts could greatly exceed those of Katrina in New Orleans," Ralph said. While California has flood control infrastructure, he said, "the possibility exists for some of that being overwhelmed."

Hotter days, nights that don't cool

The state is expected to get more heat waves, and they will be different from what California had before the last few decades, said Gershunov with Scripps. Not only will it be hotter, but it will be more humid at night with not much cooling off.

The corresponding threat to people is severe, he said. During the 2006 heat wave, 147 people died from overheating, Gershunov said. And the toll from those high temperatures is much higher, he said, if you count people with pre-existing conditions that were exacerbated by the hot weather.

Many who died were older people who had air conditioning but did not turn it on, he said, but there also was a group of migrant farm workers in their 20s and 30s who perished.

Research shows that not only will the heat waves continue, they could be more often and stronger, Gershunov said. "We've already seen changes, and they're predicted to get much more extreme. They're projected to be stronger along the coast, where most of the people live and where most people don't have air conditioning."

That will amplify demand for electricity, said Maximilian Auffhammer, a professor in the Department of Agricultural and Resource Economics at University of California, Berkeley.

If you looked at the worst of summer high temperatures that typically are only experienced for a few days now, "by the end of the century, the majority of your climate days will be like that," Auffhammer said. "What this warming will lead to is people either operating air conditioning more consistently," he added, or buying it if they don't have it.

"By end of the century, electricity consumption will be 50 percent higher," he predicted. And that number just assumes that the existing number of air conditioners are operated more often. It doesn't take into account population growth, he said. There are some projections that California's population could double to 74 million people by 2100.

"If you add population growth and climate change on top of each other, you get into some scenarios that electricity consumption is going to rise pretty dramatically, unless we figure out ways to increase efficiency," Auffhammer concluded.

Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. www.eenews.net. 202-628-6500

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