Suppose that some category of product, such as cars, becomes more fuel-efficient across the board. You might expect the outcome to be that someone who now drives 12,000 miles per year in a 30-mile-per-gallon car will start driving 12,000 miles per year in a 40-mile-per-gallon car, saving 100 gallons of gas. But according to Tierney, what tends to happen instead is that the driver with the 40-mile-per-gallon car will start driving more. If he drives an extra 4,000 miles each year, that will totally wipe out the gas savings from increased fuel efficiency, in what's known as the "energy rebound effect." And this effect, Tierney claims, is often so large that it more than offsets the savings from energy efficiency, resulting in higher total energy use. It's like the case of a dieter who sees that baked potato chips contain only 1.5 grams of fat per serving and thinks, "Great, I can eat a whole bag of these for the same amount of fat as just a handful of regular chips," and consequently takes in far more calories overall.
Now, I can see how the rebound effect could potentially lead to higher energy use, although I should point out that Tierney doesn't provide any actual data to show that it does so in reality. (The closest he comes is citing two studies that say rebound effects "could sometimes erode all the expected reductions in emissions.") But I have to say, I'm not really sold on this argument. It's true that a person who's bought an energy-efficient car might start driving more—or, at the very least, might not make as strong an effort to drive less. But most people I know don't have all that much flexibility as to how much driving we do. The daily commute, for example, is usually of fixed length. Someone who lives 10 miles from work, and consequently drives 20 miles a day (or roughly 1,000 miles a year) getting to and from work, will use less gas driving those 1,000 miles at 40 mpg than at 30 mpg. True, that person will now have less of an incentive to bike to work or carpool as a way of saving gas, since the amount of gas used on each trip will be less. But I suspect that people who bike to work now aren't suddenly going to stop doing so just because they've bought a more fuel-efficient car. ("Well, on the one hand, I do get more exercise this way, and it's better for the environment, and I can steer around traffic jams—but on the other hand, this car is so efficient, it seems a shame not to use it.")
Tierney also argues that more fuel-efficient cars pose another drawback: their smaller size makes them less safe. "Because of the smaller and consequently less safe cars built to meet federal fuel-efficiency standards starting in the 1980s," he claims, "there were about 2,000 additional deaths on the highway every year, according to the National Research Council." I have one word for this argument: hogwash. Today's cars (and I do mean cars, not SUVs) are both much more efficient and much safer than those built fifty years ago. Check out this video made by the Insurance Institute for Highway Safety, in which a 1959 Chevy Bel Air (which got about 17 mpg at highway speeds) is crashed into a 2009 Chevy Malibu (30 mpg). The before-and-after photos from the crash show that the passenger compartment in the Bel Air is crushed, while that in the Malibu remains intact. Clearly, it is possible to make cars more efficient without making them less safe.
Ah, but, Tierney points out, there is an "indirect rebound effect" as well. Even if drivers don't respond to increased fuel efficiency by driving more, they may opt to "use the money they save on gasoline to buy other things that produce greenhouse emissions, like new electronic gadgets or vacation trips on fuel-burning planes." Again, I think this connection is highly doubtful. For one thing, wouldn't a driver with a more fuel-efficient car be more likely to opt for driving as opposed to flying? (Actually, if this article is to be believed, that's not really an improvement—but that's a subject for a separate entry.) And also, aren't the type of people who buy fuel-efficient cars also the type of people who would be more likely to invest the savings in other products that benefit the environment, like organic produce or better insulation? (Or is Mr. Tierney going to argue that insulating your home is a bad idea too, because it will only encourage you to turn up the heat and strip down to your shirt sleeves? He does apparently think that buying more efficient light bulbs will only encourage you to increase the light level in your home, as he points out that "we spend the same proportion of our income on light as our much poorer ancestors did in 1700," even at much less per lumen. But does it follow from this that if I go out and buy a dozen compact fluorescent bulbs to replace less efficient incandescents, I'll look at my lower electricity bill the next month and think, "Wow, at these prices, I could put strobe lights and a huge disco ball in the garage"?)
Now, I'm not trying to dispute Tierney's conclusion, which is that energy efficiency standards alone are not sufficient to make a dent in global warming, and we also need to "consider alternatives like a carbon tax." Certainly, when facing a problem as massive and as threatening as global warming, we need to use every available tool. But I do confess myself skeptical that efficiency standards are, in and of themselves, destructive. They're not going to solve global warming by themselves, I grant that freely. But it's going to take more solid data than Tierney provides in his column to convince me that they're actually harmful.