PAUL CRUTZEN: Geoengineering might be described as human tinkering on a global scale, especially with the goal of rebooting atmospheric processes. But potential “big fix” approaches to climate change — constructing immense space mirrors to deflect solar radiation, say — are often derided as science fiction that diverts talent and financing from more plausible solutions. John Holdren, for one, as president of the American Association for the Advancement of Science, noted its “combination of high costs, low leverage and a high likelihood of serious side effects.” So it was with considerable surprise in late 2006 that Paul Crutzen, one of the most prominent and respected atmospheric chemists in the world, proposed cooling the earth by pumping millions of tons of sulfur into the stratosphere. It would be the man-made equivalent of a volcanic eruption, spreading a thin layer of particles around the planet and increasing its reflectivity. Crutzen’s proposal appeared in the scientific journal Climatic Change, but the mainstream media quickly picked it up and set off a fierce debate over the ethics and efficacy of such large-scale human interference with the atmosphere. Crutzen, who won a Nobel Prize in Chemistry in 1995 for his work on the the ozone layer, was feeling deeply frustrated. “I saw how little action was taking place on reducing greenhouse emissions,” he says. He published his article in desperation, hoping that “maybe this is a way of reducing the heating rate in the atmosphere.” Natural science backs Crutzen up. After the massive 1991 eruption of Mount Pinatubo in the Philippines, the resulting haze of sulfuric acid in the stratosphere temporarily lowered global temperatures by nearly a full degree. Doing this ourselves is complicated, of course. The sulfur would have to be carried aloft by rockets or balloons — and every year or two, at a cost of untold billions of dollars. For Crutzen, the article was intended to be provocative, to prod the discussion and encourage research. “Although I want it to be debated, to test whether this solution is feasible, looking for side effects is very essential,” he says. Such side effects could be profound, like a diminished ozone layer. “It’s not really a nice experiment to put a million tons of sulfur into the stratosphere,” he says. “It’s a quite dirty experiment.”
CARBON SEQUESTRATION: The United States has proven coal reserves of 275 billion tons, enough to supply our current energy needs for hundreds of years. The catch, of course, is that coal is nonrenewable, messy to extract and, worst of all, emits 10 percent more CO2 than oil and 60 percent more than natural gas when it is burned. Could coal ever satisfy our energy needs without exacerbating climate change? Only if that carbon could be stored somewhere. Proponents of carbon sequestration seek to do just that. Emissions from a fossil-fuel-burning plant would be caught before being released into the atmosphere, and the resulting billions of cubic yards of CO2 would be pumped into porous layers of rock far beneath the earth or sea.Sequestration was a central part of the plan to curb emissions that President Bush announced in his 2007 State of the Union address. The flagship project was known as FutureGen, a near-zero-emission coal plant in Illinois. But the Department of Energy canceled its support for the project in January, citing excessive costs, and it is now unclear if it will ever be built. Critics deride sequestration as pie in the ground: ruinously expensive for the amount of carbon being kept out of the atmosphere. One study found that to reduce emissions from coal by just 10 percent, a volume of CO2 equivalent to all the oil pumped annually worldwide would need to be forced underground, at a possible cost of trillions of dollars. But true believers maintain that sequestration is the only way we can supply our energy needs while stabilizing atmospheric carbon. And the Norwegian government already has a functioning carbon sequestration facility on a platform in the North Sea that pumps CO2 emissions deep into the seabed. Norway might even be able to sell excess storage capacity to other European countries.
KITE-SAILING TANKERS: The last wind-powered cargo ships sailed around Cape Horn in the 1940s, having been relegated to nostalgic obsolescence by steam and then internal-combustion engines. But if a German company called SkySails succeeds, wind energy will once again power the global shipping trade. Instead of sails mounted on masts, huge, computer-controlled kites flying 1,000 feet over the water will harness the wind. Attached to ships by polyethylene-fiber ropes, SkySails’ oval-shaped kites are similar in design to those used by kite surfers and paragliders. With an area of 1,615 to 10,764 square feet, the kites can generate up to 6,800 horsepower and, in ideal conditions, cut a ship’s fuel consumption by as much as a third. Ninety percent of global trade in goods is moved by sea, and the high-sulfur diesel fuel used by most of the world’s 90,000 cargo ships accounts for an estimated 4.5 percent of the global output of carbon dioxide and 20 percent of the sulfur dioxide. The shipping industry burns 2.1 billion barrels of oil annually. SkySails claims that a universal application of its technology could keep 146 million tons of carbon out of the atmosphere each year. (An American company called KiteShip is working on a cargo-kite concept of its own.) But would that be worth the effort? While shipping’s proponents hold that bulk freight by sea is far more efficient by volume than other means of transportation, it has been estimated that the shipping industry’s CO2 emissions could increase by a third by 2020. Critics of the kites contend that other projects to reduce emissions could have greater impact and that the sail technology would never work on the largest ships, half-million-ton oil tankers. Still, cargo kites aren’t merely a question of green religion; they’re also about plain old economics. Fuel costs are at an all-time high, and those savings could help a shipping company’s bottom line. To prove the technology’s potential, last December a 10,000-ton merchant ship called the Beluga SkySails left the port of Bremerhaven, Germany, for Venezuela. Its engine power was supplemented by a 1,700 square-foot kite. The computer-controlled kite system can cost $395,000 to nearly $4 million, but Stephan Wrage, the inventor and managing director of SkySails (“My friends called me an eco-freak,” he says), claims it can save around $1,500 or more a day in fuel costs. The ship made the crossing on time and under budget.