LOS ANGELES (AP) — A decade ago, California vowed to dramatically slash greenhouse gas emissions by 2020.

With the nation's most populous state on pace to meet that target, Gov. Jerry Brown on Thursday charted a new goal to further cut carbon pollution by extending and expanding the landmark climate change law.

It will "keep California on the move to clean up the environment," Brown said in a Los Angeles park before signing a pair of bills that survived heavy opposition from the oil industry, business groups and Republicans.

Experts said going forward will be more challenging because the new goal — to reduce emissions 40 percent below 1990 levels by 2030 — is considerably more ambitious and many of the easy solutions have been employed.

"The long and the short of it is that meeting the goal will require sustained regulatory effort across all sectors of the economy," said Ann Carlson, a professor of environmental law at the University of California, Los Angeles.

California is on track to meet the 2020 climate goal that called for reducing emissions to 1990 levels by restricting the carbon content of gasoline and diesel fuel, encouraging sales of zero-emission vehicles and imposing a tax on pollution.

The state plans to build on that foundation and ramp up other efforts including increasing renewable electricity use, boosting energy efficiency in existing buildings and putting 1.5 million zero-emissions vehicles on the road, according to the California Air Resources Board, which is in charge of climate policy.

Supporters overcame strong opposition from oil companies and other industry interests to pass the legislation a year after business-friendly Democrats in the Assembly derailed an even more ambitious proposal to limit the use of oil in the state.

The new law puts "very severe caps on the emission of greenhouse gases in California without requiring the regulatory agencies to give any consideration" to how it will affect the economy and residents, the California Chamber of Commerce said in a statement.

Manufacturers in California already have higher energy costs compared to counterparts across the country and setting a new climate goal without providing cost-effective options "contributes to an already challenging business environment for manufacturers," Dorothy Rothrock, president of the California Manufacturers and Technology Association, said in a statement.

Since California became a green leader by passing the climate change law a decade ago, the state has seen a flourishing clean-energy industry, said Carlson, the UCLA law professor.

"One big accomplishment to date of California climate policy is demonstrating that we can cut greenhouse gases and still achieve impressive economic growth," she said in an email.

Brown, a Democrat who has traveled the world promoting greenhouse-gas reduction efforts, issued an executive order last year setting the new 2030 goal. On Thursday, he also signed a companion bill that provides more legislative oversight of the appointed state air resources board and gives aid to poorer areas that lawmakers say have suffered the most harm from climate change.

Despite pushing the climate goals through, the centerpiece of the state's effort to combat global warming remains in jeopardy.

The law doesn't address the cap-and-trade program, which requires companies that spew greenhouse gases to buy pollution permits that are auctioned quarterly. The funds can be spent only on programs that reduce carbon pollution. After impressive sales early on, the last two permit sales have fizzled, prompting concerns that funding won't be available to continue programs in the long run.

With the uncertainty over the cap-and-trade program, the expanded climate change law "is a point on a map, but the roadmap to that point has not been filled in yet," Dan McGraw, a Houston-based carbon analyst with the ICIS trade publication, said in an email.

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Associated Press writers Don Thompson and Juliet Williams in Sacramento contributed to this report.

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Follow Alicia Chang on Twitter: @SciWriAlicia