In it's lifetime an average petrol car produces 28 tonnes of CO2 plus between 5.6 tonnes and 9 tonnes (depending who you believe) during it's manufacture. (mostly in the production of steel)
An electric car requires the production of more CO2 to manufacture (17.5 tonnes)but assuming all low carbon electricity for driving.
So yes it's a saving ........ but it's a hell of a long way from, zero and actually might make things a bit worse in the short time as you will be scrapping IC cars before the end of their lives
whereas keeping them running until then maqyl produce less CO2
Also somebody needs to point out to the environmentalists who are so tunnel vision on automobiles that that is not the only big CO2 producer
It's a lot of various things ........
did you know that 8% of Global CO2 production is due to the manufacture of concrete ?
9% steel manufacture, Each tonne of Aluminium manufactured produces between 12 and 17 tonnes of CO2
there are many other things that need looking at but most are being ignored in favour of the IC engine
....... granted it has to go, but some sort of logic needs to be used not just a helter skelter approach