It seems rather naive to say that cars are 'responsible' for climatic instability. There are many other factors that have contributed to the rapid climate change coming into effect now. Factories are the largest problem - there are many regulations in place but unfortunately adequate inspections are not being done.
What has contributed to current climate change is not cars being driven today - emissions inspections have become stringent enough to bring this into check in most areas of the world. What has affected current climate change is, yes, cars from the 70's when there were little to no regulation on emissions, but as the world rebuilt following world war two right through to the 80's large corporations polluted to their heart's content as politicians looked the other way simply because the economy was being driven out of recession.