SACRAMENTO — Farmers have always been gamblers, long accustomed to betting on the probabilities of the weather. But for the Napa Valley, where the temperatures have been ideal for the wine industry, the changes could be significant.

"They're used to rolling the dice every year," said Stuart Weiss, a conservation biologist and chief scientist at the Creekside Center for Earth Observation.

"Now, though, climate change is stacking the dice," said Weiss, who works with the center to assist growers and municipalities dealing with disruptions caused by the changing climate.

Over the next 30 years, Weiss estimates, the temperature in the Napa Valley will rise by 1.8 degrees -- an 80 percent jump over previous rates, which were about 1 degree every three decades since temperatures were first recorded in 1896.

He has turned worries about climate change into a business opportunity: His other company, Viticision, consults with growers facing the shifting conditions on their land.

Alterations in the California climate have prompted the insurance industry to assess the potential damage and its financial exposure.

The nation's crop insurance system, a hybrid of private insurers backed by the U.S. Department of Agriculture's Risk Management Agency, has been paying out steadily increasing amounts for weather-related damages across the country. According to the Congressional Research Serv- ice, the total went from $2.1 billion in 2000 to a record-breaking $12.1 billion last year.

This summer's drought in the Midwest is expected to further catapult insurance payments.

Although it's difficult to distinguish how many extreme events would have occurred without the atmospheric concentration of carbon dioxide, the Risk Management Agency now has identified climate change as one of the major risk factors for U.S. agriculture.

In a 2010 report, it paid particular attention to the vulnerabilities of California, which produces 95 percent of the country's apricots, almonds, artichokes, figs, kiwis, raisin grapes, olives, cling peaches, dried plums, persimmons, pistachios and walnuts.

"Since the production of these commodities is so concentrated into one geographical area, the climatic impacts in these agricultural markets could be profound," the report concluded.

Adaptation strategy

The agency even suggested an adaptation strategy that sounds like the breeding efforts already under way at nurseries across the Central Valley: more research into "drought-tolerant, heat-tolerant, and other crop varieties better suited to the changing conditions."

The California office of the Risk Management Agency is considering whether year-round farming is a reasonable risk for the agency to assume in the Central and Imperial valleys, where water stresses are intensifying.

In the Central Valley, the agency is considering requiring farmers relying on nonirrigated water to fallow some land during the summer months to hedge against potential losses when water supplies fall short.

And last year, the agency withdrew its insurance rating for parts of Imperial County, which it determined was uninsurable for proposed wheat farming due to concerns about the reliability of the water supply.

The high volatility associated with climate change prompted a team of Silicon Valley entrepreneurs to found the first insurance company to focus exclusively on insuring against swings in the weather.

David Friedberg was a corporate development executive at Google before founding The Climate Corp. in San Francisco in 2006, as farmers found themselves at the front lines of climate change.

One likely result of the atmospheric tumult, he said, is rising food prices.

"Farmers are having to hedge and pay for insurance claims," he said. "That increases the price of food, and when they experience losses, we and others pay them for those losses, but that also means their food is not being produced."

Cherries feel the heat

For a look into the future, look at the state's cherry crop.

Last April, the cherries were blooming in the Colombini family orchard in the San Joaquin Valley, their blossoms a signal that the harvest would be coming in six weeks.

But there was trouble lurking under those delicate blossoms. Jeff Colombini, director of the family company, Lodi Farming, pointed to the erratic blooms on his trees -- a blossom here and there but many stunted, half-grown blossoms. That is a sign, he said, of the "stresses that come with not enough chill hours."

Most of the highest-quality cherry varieties in the state are tuned for a November or December chill, which functions to slow down the metabolism of the nascent fruits and thus elongates the ripening process that comes with the onset of warmer weather.

For a perfect California cherry, the trees need 1,200 to 1,400 hours of "chill time."

But Joseph Grant, a UC Cooperative Extension farm adviser based in Stockton, said that lately, cherry growers have been seeing more like 1,000 to 1,100 hours per season.

Another factor may be the fog: Early results from a study at UC Berkeley's College of Natural Resources suggest that a lack of the usual fog hours also might be contributing to overheating of cherry buds.

While the overall cherry crop recovered late in the season, the effect of the shortened chill, according to Grant, is declining quality of California cherries.

They're shrinking in size, and the extended ripening time means the cherries are not as firm.

"What's happening," Grant said, "is that the climate here around Stockton is looking more and more like the climate down in Bakersfield."

This story was produced by the nonprofit Center for Investigative Reporting, the country's largest investigative reporting team, in collaboration with KQED public radio. For more, go to www.cironline.org. Mark Schapiro can be reached at mschapiro@cironline.org.