In An Inconvenient Truth, Al Gore produces a graphic of the cities to which he has flown (sometimes by private jet) to talk about climate change. There are dozens of them, all over the world. I am glad that he gave those talks—his contribution to the fight against climate change is equal to that of all other environmental campaigners put together. But I was shocked not so much by his mode of travel as by his total lack of embarrassment—even, perhaps, of awareness—about the contradiction between what he was saying and what he was doing.
In Europe, where the environmental impacts of transport have been subject to furious debate for years, a climate change campaigner would never have exposed himself in this way. Had he flown as much as Gore, he would have felt it necessary to explain that he could not otherwise have been so effective. He would never set foot in a private jet. He might have conducted his talks by video link–and made a point of that in the film.
Jets produce staggering amounts of carbon dioxide and other gases that accelerate global warming. But in North America the impacts of transport—especially flying—are only beginning to nudge the political surface.
Carbon dioxide emissions per passenger mile from a standard airliner are very similar to those from cars. But you can cover nearly 15,000 miles in one day by plane. The CO2 produced by planes is augmented by the other greenhouse gases they release, magnifying its effect by 270 percent. This means that flying is one of the most destructive things we can do.
It appears that the only ethical option—and I realize that this will be an even less popular message in North America than it is in Europe—is greatly to reduce the number of flights we take. Because our economy has been built around the rapid mobility of goods and people (the volume of US airfreight grew by 372 percent between 1980 and 2004), this could be our greatest political challenge.
Officially, transport is the world’s second-fastest-growing source of CO2 emissions; between now and 2050, they are expected to double. But these numbers tell only half the story. The fastest-growing source of carbon emissions is the power sector, whose output is expected to quadruple by mid-century. But much of this growth should in fact be attributed to transportation, as it is partly driven by the use of coal and gas to make synthetic liquid fuels used for vehicles. Cars and planes could soon become the primary cause of global warming.
The automobile problem is—in engineering terms—relatively easy to address: All the necessary technologies required to slash emissions from surface transport exist already. But dealing with airplanes is a far more complicated problem. It means confronting not just the political and cultural resistance we meet while trying to clean up emissions from cars but also massive technical barriers.
Lifting a large passenger plane into the air and keeping it there is a feat subject to strict physical constraints, and it requires a massive amount of fossil fuel. The standard jet engine has more or less reached the limits of efficiency, and there is no replacement anywhere near production. There has been a great deal of talk about “blended wing bodies”: planes in which the passengers sit in swollen wings. In principle they could cut fuel use 30 percent. But this is no more than a concept, whose stability and controllability have not been proven.