The thought experiment: What if every person on Earth had a car?

There are 1.2 billion cars in the world today, and 7.5 billion people. So we’ll need at least 6.3 billion extra cars to make sure everyone has their own. This will require 5.6 billion tonnes of steel, which is 3.5 times as much steel as the world produces each year.

On the roads, those 7.5 billion cars will occupy 36 million kilometres of road – about half the total length of all the roads in the world. Cars normally only spend about 5 per cent of their time on the road network, but there aren’t 7.1 billion parking spaces either.

Even with 95 per cent of them parked, the world’s cars currently use 6.5 billion litres of petrol a day. If this demand scales linearly up to 7.5 billion cars, the oil industry will need to increase output more than five times, sending oil prices to hundreds of dollars per barrel.

Cars today emit 2.5 billion tonnes of CO2 into the atmosphere each year. If driving habits stay the same, increasing the world fleet to 7.5 billion cars will add another 13 billion tonnes per year. That’s nearly half the current CO2 produced globally by humans.

Read more thought experiments:

• What is the carbon footprint of an email?
• What would happen if everyone on the planet suddenly went vegan?

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