There are an estimated 1.475 billion cars/trucks/vans in the world, as of 2023. 8 million is 0.005% of 1.475 billion.

Now, if they're going by the number of vehicles in the UK, then that number is obviously different. 41.2 million estimated vehicles in the UK. 8 million is a significantly larger percentage in that equation (19.4%). They also don't mention whether they're talking about ICE or electric cars, but I think it's safe to assume ICE. In 2023 there were 851,000 licensed zero emissions vehicles in the UK, up 57% from the prior year.

I'm a strong proponent for cutting your beef, lamb, cheese, coffee, and chocolate consumption , as they're among the worst, emissions-wise (bearing in mind this chart is by kilogram, not by calorie) by a long-shot, but we should be realistic about the things that are likely to do the most good.

We recommend four widely applicable high-impact (i.e. low emissions) actions with the potential to contribute to systemic change and substantially reduce annual personal emissions: having one fewer child (an average for developed countries of 58.6 tonnes CO2-equivalent (tCO2e) emission reductions per year), living car-free (2.4 tCO2e saved per year), avoiding airplane travel (1.6 tCO2e saved per roundtrip transatlantic flight) and eating a plant-based diet (0.8 tCO2e saved per year). These actions have much greater potential to reduce emissions than commonly promoted strategies like comprehensive recycling (four times less effective than a plant-based diet) or changing household lightbulbs (eight times less).

^https://iopscience.iop.org/article/10.1088/1748-9326/aa7541/pdf^