Do you want to lower CO2 emissions? The answer is simple.
1. Ban coal.
2. Replace coal with natural gas, nuclear, and wind.
3. Stop worrying about cars, trains, and planes. Power plants are the biggest producers of CO2 and are centralized.
4. Understand Solar is not the answer. The demand vs production curve does not work out. It is a good supplement in hot areas with a lot of sun in the summer but unless we go with orbital solar power stations it is not a good baseload solution. It just looks good and seems easy.
Why natural gas since it does produce CO2? Simple it produces about half the CO2 per BTU as coal does and is cheap. If you replaced every coal plant with natural gas you would have a massive savings in CO2 for a low cost. The next step would be to move large trucks, trains, and ships to natural gas. That would save about 20% on the CO2 they produce but since large trucks and trains have centralized fueling locations it would again be pretty simple to do.
You need to also think about the social cost of ending coal production You will be converting towns into ghost towns, Mining coal does pay pretty well and is pretty labor intensive. Sure you can retrain the miners for new jobs but those jobs will not be in the same location as the mine. You will not pay to relocate all the people in the town that depend on the mine. Think of the people that run the shops, restaurants, car lots, teach in the schools and so on. You can not get around the fact that you are going to cause a huge amount or problems and the idea of "job retraining " will not prevent it.