Until -- and unless -- there is a large mass movement against air or train travel, a person choosing one over the other is not going reduce his carbon footprint even an iota.

Let's say that Joe wants to go from NYC to DC and decides to take the train instead of flying. The same plane he would have boarded will still take off, albeit with one more empty seat. If he goes by air, Amtrak is not going to take one of the cars off of its train because Joe will not be there.

Getting on a bus to the airport instead of taking your car will make a (very tiny) difference but I am not at all certain about driving a Tesla vs a car with an internal combustion energy. Both will require the same amount of energy, be it produced by the car or transmitted over wires. In California, I suspect that most Tesla owners, given the large blackouts, have private generators to fill their batteries (an extremely fuel-inefficient method to produce electricity).

(A bit off-topic but I suspect that the wild fires in California are a major contributor of carbon -- and they double down on the damage by destroying forests which would otherwise be absorbing CO2 and replacing it with oxygen.)