We cannot stop it" much less reduce it. The amount of energy and resources this would require is far more likely to kill everything on this planet than fix anything.
You have to think in terms of planetary scale. California is a rounding error. Switching every car in CA to electrics is a rounding error. Switching everyone to solar and wind power is a rounding error.
The comparison is to every human being not being on this planet* and our technology shutting down. And in that we know we are looking at tens of thousands of years for a 100 ppm drop.
Look, I don't like this reality any more than anyone else. I just want us to stop lying so we can look at this issue from a far more honest perspective. We cannot fix this. We cannot create an artificial solution for a planetary scale problem that would take longer to solve without us around than humanity might survive.
Look at the massive forest fires we've had just this year in CA. Care to guess how much CO2 these fires released? I've done the numbers for other fires in the past. It's hard to estimate but I think it is very safe to say that these annual fires easily release YEARS of equivalent transportation CO2 into the atmosphere every year.
In fact, that's how the planetary system works!
If you go back to the 800,000 years of CO2 data there are two obvious questions anyone inquisitive enough should be asking:
How did CO2 increase without humanity around? Massive continental scale fires across somewhere in the order of 25,000 years.
How did CO2 decrease without humanity around? Weather. Rains. Hurricanes. Cyclones. Water precipitating CO2. And, yes, trees and plants growing back after the massive fires.
Destruction is always easier and faster than reconstruction. These are basic principles. If you curve fit the charts you'll come up with about 25,000 years for a 100 ppm increase due to massive fires and 50,000 to 100,000 years for a drop of the same amount due to weather.
Another question that comes up is: Well, we were able to increase it by 100 ppm in a few hundred years. How does that make any sense?
Good question. Easy answer.
We did it by burning through billions of years in accumulated energy in the form of petroleum". When we burn one gallon of gasoline in a car or one ton of bunker fuel in a cargo ship we are burning something that took an exceedingly long period of time to "manufacture". It took energy in the form of solar energy and an unimaginably large amount of raw materials (plants and animals) to produce the black goo we pull out of the ground and burn. So, yes, in a few hundred years we were able to burn energy that took millions of years and, again, unimaginable amounts of biomass, to produce.
And that's another reason for which fixing the problem is impossible. I challenge anyone to name one problem that can be solved with less* energy than that which produced it. If we start with the premise that nothing can be 100% efficient and add to that the sheer scale of the energy and mass that went into what caused this problem the answer, which is right there in the graphs, is beyond obvious. It's high school physics.
We need to stop lying if we want a chance to understand the future and make it a better one.