On the ballot measure itself, the survey showed that about one-fifth of likely voters had not yet taken a position. Forty percent favor the initiative and 38% oppose it, essentially a dead heat. Typically, experts say that a ballot initiative that has less than 50% support at this stage of a campaign faces trouble because undecided voters usually -- although not always -- tend to end up voting no.

More than two-thirds of likely voters in the survey said that global warming is a “very important” or “somewhat important” issue to them. And more than four in 10 likely voters said they have “complete” or “a lot” of trust in what scientists say on the subject, with more than two in 10 saying they have a “moderate” amount of trust.

The ballot initiative, Proposition 23 , would delay implementation of the law until California unemployment drops to 5.5% and stays at that level for a year. Unemployment is now over 12%, and a sustained level at or below 5.5% has rarely been achieved, so environmental advocates argue that the initiative would in effect put the law on indefinite hold.

California voters believe global warming is a significant issue and are inclined to trust scientific views on the subject, but they remain closely divided on a November ballot measure that would suspend the state's global warming statute, according to a new Los Angeles Times/University of Southern California poll.

Full results of the Times/USC poll on the races for governor and U.S. Senate will be available Sunday.

Campaigns for and against Proposition 23 are just now gearing up. But candidates in California's sharply contested gubernatorial and Senate races are already attacking each other over Proposition 23, which is a litmus test for many green-leaning voters.

In the battle to succeed Gov. Arnold Schwarzenegger, Democrat Jerry Brown opposes the measure. Republican Meg Whitman said Thursday that she will vote against the initiative, but would nonetheless suspend the global warming law for a year if she is elected.

In the Senate race, incumbent Democrat Barbara Boxer, chairman of the Senate Environment and Public Works Committee, opposes Prop. 23, while her GOP rival Carly Fiorina has endorsed it.

The initiative's main funders are Valero Energy Corp. and Tesoro Corp., two Texas-based oil companies with refineries in California, along with Koch Industries, a Kansas-based oil conglomerate that has fought federal climate change legislation.

The survey of 1,511 registered voters, including 887 considered likely voters, was conducted for The Times and the University of Southern California College of Letters, Arts & Sciences between September 15 and 22. The polling was conducted by two national survey research firms, the Democratic firm of Greenberg Quinlan Rosner and the Republican firm American Viewpoint. The margin of error for the likely voter sample is plus or minus 3.3 percentage points.

Carbon dioxide and other greenhouse gases are trapping heat in the Earth's atmosphere, warming temperatures on land and in the oceans, according to scientific studies. California has begun to feel the effects, with rising sea levels, the disruption of habitats for plants and animals, and diminishing mountain snowpacks that are critical to the state's water supply.

California's global warming law, also known as AB 32, is the most sweeping in the nation, requiring greenhouse gas pollution to be slashed to 1990 levels by the end of the decade, and setting a goal of an 80% reduction by mid-century.

Over time, the law would affect nearly every industry and household in the state, with regulations to cut the carbon intensity of gasoline, require auto companies to build more fuel-efficient cars, force electrical utilities to switch to solar and wind energy, make buildings and appliances more energy-efficient and encourage denser development with access to public transportation.

The findings of the Los Angeles Times/USC poll are similar to a July poll by the Public Policy Institute of California, a non-partisan think tank. Two-thirds of Californians in the PPIC survey said they favored the existing greenhouse gas law, but likely voters were evenly split on whether the state should “take action right away” or “wait until the state economy and job situation improve to take action.”

--Margot Roosevelt

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Video: USC professors discuss poll results

Photo: An activist opposing Proposition 23 hands out a flier to a passing motorist at a rally in front of a Valero gas station on Sept. 18. Credit: Mariah Tauger / Los Angeles Times