Gavin Newsom, the California governor, packed his bags and his ambition Monday and flew to Chinese provinces on a weeklong mission to negotiate Climate agreements.

Last month, he was the only American invited to address the United Nations about climate change, where he excoriated the fossil fuel industry for what he called its decades of “deceit and denial.”

He has signed a raft of laws and regulations to speed the nation’s most populous state away from fossil fuels, including a ban on the sale of new gas-powered cars by 2035 and a mandate to stop adding carbon dioxide to the atmosphere by 2045. He wants to end oil drilling in his state, a major oil producer, also by 2045.

The two-term Democratic governor wants California to set an aggressive pace for the nation — and the world — as time is running out to deeply cut the carbon emissions that are dangerously heating the planet. Mr. Newsom’s bold moves on climate have elevated his national profile, just as he is widely believed to be preparing for a White House run in 2028.

“We move the needle for the country and, as a consequence, for the globe,” Mr. Newsom said in a telephone interview Sunday night from Hong Kong. “And that is profound.”

Critics warn that some of Mr. Newsom’s climate policies are so ambitious as to be unrealistic, making them impossible to scale on a national or global level. Worse, they say, his headlong pursuit of his goals could disrupt California’s energy supplies, hike electric rates and devastate communities that depend on gas and oil drilling.

“The Newsom administration has been pushing harder and faster on a climate policy process that was already in place,” said David Victor, co-director of the Deep Decarbonization Initiative at the University of California San Diego. “The challenge is how hard and fast can you push the system ‘til it breaks?”

Mr. Newsom said that technological changes in the way the United States produces and uses energy are happening so fast, that it makes sense to set ambitious targets. “The breakthroughs that are coming in the next few years will blow past the paradigm of limited thinking we have today,” he said. “We have proven again and again that through policy we can accelerate innovation.”

In China this week, Mr. Newsom plans to sign five agreements with leaders of Chinese provinces aimed in part at exporting some of California’s climate policies and technologies.

Mr. Newsom’s posture as a climate warrior would seem to help him in 2028, when Gen Z and millennial voters will dominate the electorate, said Celinda Lake, a Democratic pollster and political strategist.

“The 2028 president is going to have a base among young voters and they’re going to want to see that he’s been in the trenches of the issues they care about — if he makes it work,” Ms. Lake said.

Many of Mr. Newsom’s constituents see his zeal as the proper response to the wildfires, storms and drought that have devastated the state and been made worse by climate change. A February poll by the Public Policy Institute of California found that three in four Californians think it is necessary to take immediate steps to counter the effects of climate change.

But Vince Fong, a Republican state assemblyman from Kern County, where the state’s oil industry is based, said that Mr. Newsom is charging ahead with high-level plans to slash emissions and shut down drilling with little regard for how to manage the economic fallout.

“Governor Newsom is very good at the political rhetoric of demonizing energy production,” said Mr. Fong. “But his policies are not grounded in economic reality.”

Mr. Newsom joins earlier California governors who pushed the state to the vanguard of climate policy, including Jerry Brown, a Democrat who promoted rooftop solar and later traveled to China to talk climate policy with president Xi Jinping, and Arnold Schwarzenegger, a Republican who helped craft the nation’s first major law to require cuts in greenhouse gasses and developed tailpipe emissions regulations that became a national model.

But Mr. Newsom, 56, has seized the climate mantle and made it his own. On top of the mandates to end emissions and compel sales of electric vehicles, he pushed California legislators to approve a record $52 billion in climate spending. Earlier this month, he signed a first-in-the nation law that would require major companies to publicly disclose all their greenhouse emissions.

And his administration is suing the world’s largest oil companies for the climate damages linked to their products. In addition, California has nearly stopped issuing new permits for oil and gas drilling. And it has created an agency to monitor oil companies for price-gouging or other illegal activities.

The governor says that while California helped give birth to the American oil industry in the 19th century, he sees no place for it now.

Oil drilling makes up less than 1 percent of the state’s gross domestic product and accounts for about 2 percent of its employment, said Ranjit Deshmukh, a professor at the University of California, Santa Barbara, who co-authored a paper on the economic impacts of California’s decarbonization policies. Production peaked in 1985.

Most of the state would be unaffected if oil drilling were to stop but it would devastate Kern County, where California’s fossil fuel industry is concentrated, Mr. Deshmukh said.

Chad Hathaway, who owns a 27-employee oil company in the county, feels like his community doesn’t matter to Mr. Newsom. “In his mind, it’s like we’re people he can afford to lose,” said Mr. Hathaway, a fifth-generation Californian.

“He treats us like we’re this evil empire,” he said. “I worry about my employees, I worry about my family, I worry about all the investment I’ve made in California in 20 years.”

Mr. Newsom said his administration is helping Kern County transition to a new economy and pointed to $120 million the state has invested to cap thousands of its abandoned oil wells. “These are great jobs,” he said. “It’s the same workers, the same skills.” He noted that Kern County is also home to a fast-growing solar industry.

The governor has less empathy for the multinational oil companies he is suing, including Chevron, which is headquartered in his state.

“I’ve had it with those guys,” Mr. Newsom said of the oil companies. “They knew more than the rest of us did about the devastation their product was creating. They claim climate change is real now, but they’re not investing in the solutions. We’re the only ones putting money to help with the transition. They’re not doing a goddamned thing.”

“Yes, I use their product,” he said. “And yes, I flew over here. And yes, I’m in a car that uses gas. I’m not stupid. I’m not naïve. I didn’t walk here in my organic moccasins. But nor am I naïve about their deceit and their denial and as a consequence of the delay and how that’s literally accelerating the destruction of our planet.”

A Chevron spokesman declined to respond to Mr. Newsom’s criticisms and was dismissive of the state’s lawsuit. “Climate change is a global problem that requires a coordinated international policy response, not piecemeal litigation for the benefit of lawyers and politicians,” said the spokesman, Bill Turenne Jr.

For all the governor’s climate ambitions, California is not on track to meet its own 2030 emissions reductions target.

“Well, we’ve got work to do,” Mr. Newsom said on Sunday. “The work is exciting. You ain’t seen nothing yet. We got work to do and every year we iterate.”

After the California legislature passed a landmark bill last month requiring large companies to disclose all their greenhouse gas emissions, Mr. Newsom appended an unusual note to his signature on it, noting that the deadlines are “likely infeasible” and asking legislators to work on a new law to modify it.

And in an acknowledgment that the state may not be able to produce renewable electricity fast enough to replace its old polluting power sources, Mr. Newsom wants regulators to extend the life of Diablo Canyon, the state’s sole nuclear power plant for another 20 years. The plant, which supplies about 9 percent of the state’s electricity without emitting greenhouse gasses, is scheduled to close in 2025.

“Before I got elected I never heard of cleanup legislation,” said Mr. Fong. “His argument is, this will have costs but we’ll clean it up later. That’s not how you make economic and energy policy for 40 million people.”

One area in which California appears to be zooming ahead to meet its climate targets is in the adoption of all-electric vehicles.

In the second quarter of 2023, 25 percent of new cars sold in the state were electric (compared with 7 percent nationally), putting California on track to meet Mr. Newsom’s mandate that by 2035, every new car sold in the state will be electric.

Charging stations are moving even faster. The state has already met the governor’s goal of installing 10,000 fast-charging public stations by 2025.

“California is blowing these targets out of the water,” said Sara Rafalson, a vice president at EVgo, an Oakland-based charging company, who credits Mr. Newsom for the work.

But as the E.V. network spreads, utilities are facing a challenge: how to supply the additional electricity required.

A report by Southern California Edison, one of the state’s largest electric utilities, found that meeting Mr. Newsom’s climate mandates would cause demand for electricity to spike by more than 80 percent, primarily because of electric vehicles. That rising demand comes as utilities would be required to rapidly slash their greenhouse emissions.

To meet Mr. Newsom’s climate goals, Southern California Edison would need to invest heavily in wind and solar energy while erecting transmission lines and towers four times faster than it does now and building smaller distribution lines 10 times faster. And it would need to keep that pace going for 20 years — at a cost of more than $370 billion.

“We are rebuilding the plane while we’re flying it,” said Pedro Pizarro, the CEO of Edison International, the parent company of Southern California Edison.

And even that won’t be enough, he said. To keep the lights on and the cars charged, the company would have to continue to run its existing fossil fuel-fired plants but equip them with costly technology designed to capture carbon emissions before they are released into the atmosphere. That nascent technology is not yet in commercial use and no power plant in California currently uses it.

“It’s not that the emperor doesn’t have clothes, but the clothes are pretty thin,” said Mr. Pizarro.

Some California companies say that while they find the Newsom climate regime burdensome, they also see it as inevitable.

Hamid Moghadam, CEO of Prologis, a San Francisco-based company that builds and leases warehouses for products ordered online from retailers like Home Depot,

said that his global business must comply with 19 California climate regulations, ranging from rules that limit carbon dioxide emitted from cement manufacturing to restrictions on emissions from the delivery trucks. The rules can add roughly 6 percent to project costs, he said. “It drives up the cost of building, leasing and maintaining the warehouses, which drives up the cost to the consumers.”

Still, he said, “the smart companies are looking at the climate thing as a business opportunity and instead of fighting it, the forward-looking ones that have the capital are embracing it. Twenty years from now we’ll be looking at what we’re doing today in California as the norm.”