Small cars of any kind are certainly the way to go if you want to minimise carbon. Even a petrol supermini probably has lower cradle-to-grave emissions that a Chelsea tractor-scale EV.
I came across this very good article. It uses UK assumptions for grid carbon intensity, makes some quite broad generalisations and simplifications but I think does quite a neat job of explaining the factors involved in ICEs vs EVs and CO2 emissions, without getting bogged down in the evils of lithium mining, putting out EV battery fires on the hard shoulder, etc etc.
How much electric vehicles actually help to cut carbon emissions to mitigate climate change can be confusing. Here we compare buying EVs new or used against the emissions of petrol and diesel cars, and which cars avoid the most carbon emissions over their life cycle.
www.zerocarbonguildford.org
For us Cali owners it's a useful basis for pondering whether (in carbon terms) it makes sense to buy a small EV to use alongside a Cali, rather than just using the Cali for everything. Based on the article, and some other assumptions:
Based on daily drive miles (ie not holidays, moving Aunt Mabel's sofa, etc): 10,000 pa
Cali emissions per mile: 211g (T6 148bhhp)
Small EV emissions per mile: 45g (from article, based on UK grid intensity)
Avoided emissions by using EV for 10k daily drive miles, per year: 1.7 tonnes approx
Embodied carbon for second car (small EV): 14 tonnes (from article)
Payback time: 8.2 years
Hmmm....