AIRLINES STUCK IN THE KEROSENE AGE
But air transport presents the biggest problem. "The gas turbines in long-distance flying, that's the only way to go," says Smil. "There is no [replacement] on the horizon." Those same massive, kerosene-powered turbines propel every Airbus, 747, and cargo jet in the world. Even if engineers could devise aircraft that use electricity to travel at the speed of jets (and nothing like that exists – electric dirigibles notwithstanding), there's no way to carry the energy needed to propel such an airplane: The best batteries weigh 50 times more than jet fuel per unit of energy stored.
It means that the only renewable option for transportation, especially air transport, will be biofuels produced from corn, soy, sugar cane, and other sources – this, despite the fact that they demand enormous amounts of land and water, and may well encourage deforestation.
Continuing to rely on fossil fuels beyond a certain point will have consequences. Since the start of the Industrial Revolution, carbon dioxide in the atmosphere has risen from 280 parts per million to 380 p.p.m. Many climatologists now believe that letting it rise to a "red line" of 450 p.p.m. (which could happen by 2080) would trigger catastrophic changes, such as the melting of the Greenland and West Antarctic ice sheets. Steven Davis, a climatologist at the Carnegie Institution for Science in Palo Alto, Calif., has looked at how to avoid crossing that critical line.
In a paper published in the Sept. 10 journal Science, Mr. Davis reached a surprising conclusion. He calculated that if every Humvee, power plant, and other fossil fuel-burning device on Earth was used until it wore out – and then replaced with a carbon-neutral device – carbon dioxide would peak just below the red line.
In a way it's good news.
"It may suffice to get existing coal-burning power plants to commit to scheduled shutdown dates, and not to spend political capital on shutting them down early," says Davis.
If that plan were followed, typical shutdown dates for power plants might be 40 years away, creating the illusion of time to spare, says Davis. But his scenario, Davis says, "is still pretty radical" because every day, new automobiles and airplanes continue to roll off assembly lines around the world.