Cars off the road

M&S unveils carbon-neutral target (BBC News):

M&S said the carbon savings it aimed to achieve under its plan would be like taking 100,000 cars off the road each year.

Lately, I’ve been seeing a lot of environmental plans being measured in the number of cars taken off the road. I did a search on Google News and came up with a long list. I’ve selected a few below:

Earth Hour’s initial goal is to reduce Sydney’s greenhouse gas emissions by 5 per cent over the next year, the equivalent of eliminating 75,000 medium sized cars off the road for one year. (Sydney Morning Herald)

The Greater Gabbard (GG) scheme supplying 500MW through 140-turbines will cut CO2 emissions by 1.5m tonnes a year – the equivalent of taking 350,000 cars off the road. (Press Release)

The California standard, Schwarzenegger said, will reduce carbon emissions by 13 million metric tons annually, equal to taking 3 million cars off the road. (Washington Post)

Just supplying Americans with plastic water bottles for one year consumes more than 47 million gallons of oil, enough to take 100,000 cars off the road and 1 billion pounds of carbon dioxide out of the atmosphere, according to the Container Recycling Institute. (SFGate)

While reducing carbon dioxide emissions is a good thing, I wasn’t sure whether measuring emissions in units of ‘cars’ is the best idea. It’s not a bad idea – it’s a very familiar unit to people, and everyone knows that cars produce pollution. And certainly companies and politicians like it, because it results in impressively high-sounding numbers, given the standard benchmark of 1 car = 4.3 metric tonnes of carbon dioxide. But do people really understand it? Exactly how many ‘cars of pollution’ are on the road? Indeed, at the rate that cars are being taken off the road, you begin to wonder whether there’ll be any cars left soon – or more pertinently, how much do cars actually contribute to total carbon dioxide emissions?

Based on this government report (Defra), road transport accounted for about 22% of carbon dioxide emissions in the UK in 2005. That 22% represents 120 million tonnes of carbon dioxide – or about 28 million ‘car units’*, which means that the UK’s entire emissions are equivalent to 129 million cars. That’s a lot of cars to take off the road – but not as many as I’d expected. So perhaps the measurement isn’t as bad as I thought, although it wouldn’t hurt reporters to put their measurements into context.

Yeah, like that’ll happen.

*There are about 32 million real cars in the UK, so the estimate of 4.3 tonnes per car isn’t bad at all, when you average things out.