With China mulling an eventual ban on sales of cars with gasoline or diesel engines, the world's largest car market made it clear earlier this month that it intends to force a conversion to zero-emission vehicles.

Now California, which has led the U.S. in environmental awareness and emission reduction for decades, is doing the same.

Governor Jerry Brown is interested in the idea, noting that China could take a leading role in reducing climate-change emissions—one that his state has claimed for 70 years.

DON'T MISS: Will California lead the green-car resistance? (Dec 2016)

Mary Nichols, head of the powerful California Air Resources Board, told Bloomberg in an interview Friday that Governor Brown asked her, "Why haven’t we done something already?"

Any such ban, she said, would be at least 10 years away at the earliest.

But that's a short interval for planners at the world's large global automakers, whose product cycles run five to seven years—and who are already planning vehicles to be sold in the early and mid 2020s.

California Air Resources Board chair Mary Nichols (via Twitter)

California Air Resources Board chair Mary Nichols (via Twitter)

If California were to enact a ban on sales of new vehicles with combustion engines, it would continue the state's leadership role in the U.S. climate resistance to the Trump Administration denial of climate science.

Nichols, described by The New York Times on Wednesday as an "electric-car-driving, hoodie-wearing, 72-year-old air quality regulator," leads a body with enormous power to set both vehicle rules and climate policy for the U.S. market as a whole.

The state regulated emissions from new vehicles well before the national Environmental Protection Agency was established in 1971, as the Times notes in its fascinating profile.

CHECK OUT: China wants all electric cars: will it work? Reasons and reactions

A series of court cases have firmly established its right to regulate emissions separately from national standards.

In 2010 and 2012, CARB joined the EPA and the NHTSA in negotiations to establish two sets of linked carbon-emission and fuel-economy standards for model years 2012 through 2017, and 2018 through 2025.

The rules adopted were essentially those California had demanded, with automakers reluctantly conceding to more stringent requirements.

1970s Los Angeles smog depicted in the Honda short film

1970s Los Angeles smog depicted in the Honda short film

That enabled them to avoid what would have been a nightmare scenario: having to measure emissions and fuel economy separately for vehicles sold in California plus a dozen or so other states that have adopted its standards versus those sold in the rest of the U.S.

The EPA (now led by climate-science denier Scott Pruitt) has reopened its 2016 decision to confirm the 2022-2025 emission reductions agreed to in 2012. The agency has indicated it could delay, modify, freeze, or even roll back those limits.

Pruitt told lawmakers in a June budget hearing for the EPA, however, that his agency did not intend to challenge California's ability to set its own standards.

"Currently, the waiver is not under review," he said.

Meanwhile, the NHTSA is now evaluating its corporate average fuel economy standards for the same period, which must align with the EPA's emission limits.

Gas pump

Gas pump

California is going in precisely the other direction, as Nichols' comments made clear.

"Embracing [a ban on sales of cars with engines] would send shockwaves through the global car industry," Bloomberg notes, "due to the heft of California’s auto market."

California's car market is far larger than that of any other state, at more than 2 million sales a year.

In fact, it's larger than the sales in all of France—one of the countries that has enacted a version of the ban on sales of new cars with engines for 2040.

With sustained, meaningful action on climate change ever more urgent in the minds of elected officials and regulators, much of the world is likely to watch like a hawk for any new emission rules emerging from Nichols' agency.

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