First, California lawmakers targeted the cars we drive in their campaign to curb global warming. Then they turned their attention to the power plants that produce our electricity.

Now they are taking aim at the gas we burn in our cars.

A few days ago, senators passed a law to require those who make and sell fuel in the state to provide, by 2020, a mix of fuels that pump 10 percent less carbon into the atmosphere than today's blend.

The bill's requirements could be met through a variety of strategies. Those include selling reformulated gasoline or diesel fuel that slashes carbon emissions, making alternatives such as ethanol, biodiesel and compressed natural gas widely available, and introducing hybrid gas-electric cars that can be plugged into wall outlets.

Sen. Christine Kehoe, D-San Diego, the bill's sponsor, said the precise solutions will have to be worked out by a state regulatory agency and refiners. But she said that residents of San Diego and Riverside counties should not anticipate having to make any major sacrifices.

"It's a matter of shifting gears, so to speak," Kehoe said, in a telephone interview Thursday. "And it needs to be a convenient choice for the typical Californian who just wants to be able to fill up their tank and drive to work."

One likely outcome, she said, would be that ethanol and biodiesel would be much easier to find. Today, she said, the only station in the region providing those fuels to consumers is Pearson Fuels in San Diego.

The legislation, Senate Bill 210, is expected to be signed by Gov. Arnold Schwarzenegger, converting an executive order he issued in January into a state law.

Avoiding side effects

In passing the bill, lawmakers sought to ensure that Schwarzenegger's reduced-carbon mandate won't be rescinded by a future governor. And they sought to craft a strategy that avoids unwanted environmental side effects, such as worsening air quality and wasteful use of water, Kehoe said. There are concerns, for example, that widespread use of ethanol could elevate ozone levels in regions prone to smog, such as Los Angeles and the Central Valley.

Kehoe said that fuel was the natural next target in the fight against global warming.

"Forty percent of our greenhouse gas emissions here in California come from our transportation sector," Kehoe said. "If we are going to make a determined effort to reduce our greenhouse gas emissions, it has to include the fuel we burn."

Many scientists blame the growing concentration of gases such as carbon dioxide and methane in the atmosphere for the gradual warming of the Earth that they have observed over the last century. Products of vehicle and power plant emissions in the United States and burning of forests on other continents, the gases are acting like a blanket that keeps one warm at night by trapping body heat, many scientists say.

Not all scientists agree that people are responsible for the recent climate trends, or at least for the full extent of the Earth's temperature changes.

But a large number say the evidence is strong that industrial society is the major factor in the trends. And they warn that accelerated warming could lead to extensive coastal flooding, more forest fires and longer droughts across the globe, and widespread famine in Third World countries.

California first decided to do something about that threat in 2002, when legislators in Sacramento passed the nation's first state law that sought to reduce carbon emissions. That legislation targeted automakers, and in about a year, Californians will be able to buy low-carbon vehicles as the 2009 models reach car lots.

Then, by 2012, power plants will have to begin curbing their greenhouse gas emissions, as rules written in response to a law passed last year take effect.

A first for transportation fuels

When the low-carbon fuel might arrive at area service stations isn't clear, Kehoe said. But she said the California Air Resources Board, the agency that wrote the rules to implement the two earlier laws, will have two years to adopt regulations to bring about the debut of low-carbon fuel.

The debut undoubtedly will deliver sharply higher prices at the pump for motorists, as refiners struggle to produce a fuel they can sell nowhere else in the country, said Sen. Dennis Hollingsworth, R-Murrieta, who represents southern Riverside County and eastern San Diego County.

"It's a guarantee," Hollingsworth said.

He was one of 15 senators who voted against the legislation last week, in a vote that fell along party lines.

"The whole idea of carbon reductions in fuels is pretty dubious, in terms of its effectiveness," Hollingsworth said. "The less carbon you have in fuel, the less you have to burn. That means it is not as high in octane. And that means it is not going to burn as efficiently."

And all of that, he said, means more pollutants will escape and aggravate Southern California's already poor air quality "for some minuscule, if at all, effect on the carbon output of the state."

Kehoe said the bill requires that air quality not be compromised.

Others praised the bill.

"We're very happy," said Patricia Monahan, clean vehicles deputy director for the California office of the Union of Concerned Scientists, a Massachusetts-based group of scientists and activists that advocates aggressive strategies to combat climate change.

"It's the first effort ever to reduce the global warming pollution from transportation fuels," Monahan said. "California can be a model for the rest of the country and even the world."

Target is 10 percent

Monahan said her group is hopeful that the law will spur technological advances in the various alternative fuels, as well as new strategies, that will slash carbon emissions well more than 10 percent.

When it comes to goals, the latest initiative's target of 10 percent is less aggressive than those put into effect through the two earlier laws. The 2002 law requires a 30 percent carbon reduction for new cars by 2016 and the 2006 law requires a 25 percent reduction in power plant emissions by 2020.

Kehoe said she does not believe that her bill is soft by comparison.

"I think it's an aggressive first step, I really do," she said. "It's not going to be easy to define and quantify a 10 percent reduction."

And one has to remember, Kehoe said, that the 10 percent cut is from today's carbon levels. She noted that the volume of carbon emissions spewed from tailpipes continues to grow every year.

"Our state economy continues to grow, and Californians continue to drive more and more all the time," she said. "People are taking children to soccer practices across town and are meeting friends in the other direction."

Not to mention, she said, that California is driving into new territory with this legislation.

"We really are embarking on a whole new area of public policy," Kehoe said.

Contact staff writer Dave Downey at (760) 745-6611, Ext. 2623, or ddowney@nctimes.com.