I don’t buy into manmade global warming, at all.
In fact, I would have especially welcomed a little warming last month.
I just mentioned Los Angeles and Mexico City, because those cities are notorious for having smog and bad air quality, due to their geography and climate - air masses frequently sit in place for an extended period, like water in a bowl, so local pollution can build up until it makes folks eyes burn. Most other cities are naturally better ventilated.
Air quality is better now in LA than it used to be, but auto exhaust is still their number one air pollution source. Burning hydrogen in the city instead of gasoline and diesel would improve local air quality, and total carbon output be damned. Hydrogen could be produced up the the coast, over the border in Mexico, or even offshore.
California requires automakers to meet tighter fuel efficiency and pollution than the rest of the country, and they closely monitor local air quality, especially in LA. But they don’t enforce total carbon output or overall energy efficiency. So their system would be fine with wasting money or energy elsewhere, to improve what they do measure.
Hydrogen is suitable for niches like that. As the technology improves, there could be a good business case to use it in other niches, or even for widespread adoption at some point.
There are no hard showstoppers - many hydrogen cars are driving around today. They are just not the best value for regular car owners at this point.
Again, I have no bitch about LA wanting to clean up its own air — but no one has a gun to their head to live there (Mexico City either), so unless their bluejean millionaires from the entertainment industry — the ones who want to get rid of dams because they want to canoe down the “lost” canyons — want to spring for the means, they’re free to move somewhere else.