Friday, August 10, 2007

Lies, Damn Lies & Statistics

Global warming, organic produce, hybrid vehicles, low-carbon lifestyles. Just about every day brings a story about one of these topics into my inbox. The claims range from "global warming is a myth" to "get 100 mpg!" and it's always a bit of a hoot to read through and see what particular brand of pseudo-science or statistical manipulation form the basis for the claim.

I'm not a scientist, of course. But I hope that I'm a decent evaluator of information and can at least identify the whackoloons and crackpots. (Well, Snopes helps, too.)

For example, I spent a lot of time trying to explain to people on a pet food board that organic does not necessarily equal "safe" -- nor does it mean "better" or "more nutritious"-- when the pet-food tainting story came out a few months ago. There might be many reasons to choose organic produce or free-range chicken, for example, but that is no automatic guarantee of safety and goodness. Taking herbal supplements or using homeopathic remedies is not safe simply because it's "natural", whereas taking aspirin is dangerous because it's made in a lab.

Lies, damn lies, and statistics, right?

So I was amused to find an article in the Times of London that makes the rather outrageous claim that it actually "costs more" in terms of carbon emissions and energy usage to walk around the city than it does to drive. The analysis is flawed (for example, not taking into account the cost of making the automobile and providing gasoline, while counting everything in the lifetime of a cow and assuming that 100% of our energy comes from meat) but the article is in a major (read: non-tabloid) newspaper and makes some rather outrageous claims that sound persuasive and reasonable. I'm sure that most people reading the article will file it away as "correct"
Food production is now so energy-intensive that more carbon is emitted providing a person with enough calories to walk to the shops than a car would emit over the same distance. The climate could benefit if people avoided exercise, ate less and became couch potatoes. Provided, of course, they remembered to switch off the TV rather than leaving it on standby.

The sums were done by Chris Goodall, campaigning author of How to Live a Low-Carbon Life, based on the greenhouse gases created by intensive beef production. “Driving a typical UK car for 3 miles [4.8km] adds about 0.9 kg [2lb] of CO2 to the atmosphere,” he said, a calculation based on the Government’s official fuel emission figures. “If you walked instead, it would use about 180 calories. You’d need about 100g of beef to replace those calories, resulting in 3.6kg of emissions, or four times as much as driving.
Mr Goodall is a Green Party parliamentary candidate. Obviously, this sort of analysis supports his particular campaign, but the logic doesn't quite stand up to scrutiny. The article is not entirely wrong, of course -- Goodall makes some good points that we need to consider the distance that our food travels as part of the "cost", and how much energy is needed to process, store, and then cook the foods that we buy. It's not an unreasonable suggestion, of course, but the misleading claim that 'walking is worse than driving' tends to make me skeptical about the rest of his "science".

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