Geoengineering the Climate



In November 1997, University of California-Irvine physicist and best-selling science fiction author Gregory Benford wrote a reason story describing how various technical schemes might be deployed to prevent global warming. "Some geoengineering systems appear possible to deploy now, and at reasonable cost," wrote Benford. "They could be turned on and off quickly if we got unintended effects."

Benford reviewed proposals for reforestation and for fertilizing the oceans with iron to pull excess carbon dioxide out of the atmosphere. He also considered such ideas as injecting sulfate aerosols into the stratosphere and burning sulfur in ships to boost reflective cloud cover over the oceans. Benford even mentioned the possibility of building a reflective space mirror. All of the concepts except the space mirror were relatively cheap.

Twelve years later, geoengineering has become more respectable as a possible emergency measure to cool the planet down. "It's got to be looked at," White House science adviser John Holdren told the Associated Press in April. "We don't have the luxury of taking any approach off the table." Congress held its first hearings on it in November. Some of Benford's original proposals are at the forefront of the current geoengineering discussion. Chemistry Nobelist Paul Crutzen has endorsed a plan similar to the one Benford described to inject sulfate particles into the stratosphere. Stephen Salter, an engineer at the University of Edinburgh, suggests having ships inject seawater into the atmosphere, where salt particles would serve as extra cloud condensation nuclei.

In September the Copenhagen Consensus Center looked at estimates for implementing various geoengineering proposals. A space mirror turned out to be wildly impractical, at a total of $500 trillion. By contrast, a fleet of 167 F-15 airplanes flying three times per day to inject about 1 million tons of sulfur particles into the stratosphere each year would cost about $4.2 billion annually. Oceanic cloud brightening would take a fleet of 1,881 vessels, costing $5.8 billion annually.

"The next century will see a protracted battle between the prophets who would intervene and the moralists who see all grand-scale human measures as tainted," Benford concluded. "Even now, many argue that even to speak of geoengineering encourages the unwashed to more excess, since the masses will think that once again science has a remedy at hand." He added, "Some, though, will say quietly, persistently, Well, maybe science does." Twelve years later: Well, maybe science does.