1st - Global warming is real and all, but there is nothing comproving it is caused by the actions os men.
2nd - Take EUA for example, even if they banish old cars, 60% of their energy is generated from Fossiel Fuel. so nothing would change, might get even worse.
3nd - The State is what cause issues, not what solves them, so never support the State to prohibit/regulate something, it always ends bad.
Explaining because some people may have difficult understanding what im saying;
1st: There is a thing called "scientific method" and to this day I haven't yet been presented with a study made by said method that comproves the warming is caused by the actions of men. Instead, what we have are things like "Medieval Warm Period", which shows that our planet do get hot sometimes because yes.
2nd - Eletric cars still needs to be charged, to be charged they need energy and this energy in most parts of the wolrd is generated by burning fossil fuel. Thus, even if you banish old cars and force people to buy eletric cars, you would still be using fossil fuel.
3nd - This is a general thing, but you can apllie it to anything. Lets take health care price for example. Its price is high and that is a issue, a issue some people demand the State to resolve giving people "free" health care. Would that solve the issue? Hell no. What would solve the issue would be lifting the State regulations and taxes on health care sectors, which would lower the price be it because the material used to provide health care is cheaper or because there would be more people willing to invest/open their own business which would raise the competition.
If you can and if it interess you, take a time to search what regulations the State where you live impose on health care sectors or any other sector you think is important.