Calling the issue the defining difference between himself and Republican Meg Whitman in the governor’s race, Democrat Jerry Brown gave an impassioned defense Thursday of California’s landmark global warming law.

In a wide-ranging interview with the Mercury News editorial board, the attorney general called Assembly Bill 32 — now under attack by conservatives and some business interests as a job killer — “a path forward” for the Golden State. Brown said the new law would create hundreds of thousands of clean-energy jobs, reclaiming from China leadership of the cleantech economy.

“This is a powerful future,” Brown said. “I see this as the key” to job creation.

Whitman, the former CEO of eBay, has called for a one-year moratorium on implementation of the law, which is due to take effect in 2012. Her stance puts her on the opposite side of many Silicon Valley companies, including eBay.

“While she supports the goals of AB 32, she also believes we must fix its implementation so each regulation is fully analyzed based on careful economic and environmental review,” Whitman spokeswoman Sarah Pompei said.

Brown on Thursday also weighed in on Sacramento gridlock, the state’s staggering costs for employee pensions and the influence of special interests in crafting legislation. And he reiterated a willingness to release 10 years of tax returns if Whitman does too.

Hammering the global warming issue, Brown said he strongly opposes Proposition 23 on the November ballot, his first public stance on the measure. The proposition, on which Whitman hasn’t yet taken a position, would suspend AB 32 until the state’s unemployment rate drops to 5.5 percent for at least a year. In the past two decades, that has only occurred three times.

Brown’s strong statements on the global warming issue came a day after the Public Policy Institute of California released its annual survey of attitudes on the environment. The poll found that two in three state residents still support AB 32’s requirement to cut greenhouse emissions to 1990 levels by 2020.

More Californians think combating climate change will create, rather than destroy, jobs, the poll found. Just 16 percent of residents told pollsters the effects of global warming will never materialize.

A Field Poll released July 9 also found that among independent voters — who now make up 20 percent of the state’s electorate — less than a third supported Proposition 23.

“As undecided voters put together who they are going to vote for, this issue is one of two or three — along with jobs and education — that will help make the difference,” said Barbara O’Connor, director emeritus of the Institute for the Study of Politics and the Media at Sacramento State.

Whitman’s campaign said she isn’t worried about coming down on the wrong side of the issue because voters will care more about her proven record of creating jobs.

Opponents of AB 32, which Gov. Arnold Schwarzenegger signed into law in 2006, say it will hurt businesses and have little effect worldwide on greenhouse gases. Supporters say it will boost the state’s renewable energy and green technology industries, setting an example for other states and Congress.

While the California Air Resources Board continues to write the specific rules that will take effect in 2012, the regulations are expected to fall hardest on industries that burn the most fossil fuels, including oil refineries, power plants and cement kilns. Two Texas oil companies, Valero and Tesoro, provided much of the funding to qualify Proposition 23 for the ballot.

In a March debate with her primary opponent, Steve Poizner, Whitman said she had called for the one-year moratorium on the implementation of AB 32 because the law was going to drive more businesses out of the state.

“I understand why we want to own the green tech industry. We should. We have to own innovation,” she said then. “But AB 32 is not going to create more green jobs in California. The way we are going to have to do that is compete for those jobs with tax incentives and other ways to make sure we don’t lose that industry.”

Brown in the past has said he would support “some changes” in AB 32. But on Thursday, he explained that he was talking about relatively slight changes in the regulatory process, not the law itself.

In other matters Thursday, Brown:

Said he would release his tax returns only if Whitman releases hers. Brown in June agreed to the Mercury News’ request for 10 years of returns, but the Whitman campaign balked, saying Brown should release returns for all 27 years since his prior stint as governor. When asked Thursday if the returns would indicate he had cashed in on his gubernatorial years, Brown said “no.”

Agreed with Whitman that 4,000 bills per legislative session is way too many — particularly since so many are sponsored by special interests, as reported in a recent Mercury News series. Brown called for more transparency in legislation and limits on the number of bills that could be introduced, saying: “The Legislature doesn’t provide solutions. It provides legislation.”

Defended the current pension system for state employees, saying he thought it could be “mended.” Whitman has called for putting most new state workers into a 401(k)-style plan.