Superfreakonomics_ global cooling, patri - Steven D. Levitt [86]
But the best reason to reject the idea, Caldeira thought, was that it simply wouldn’t work.
That was his conclusion after hearing Lowell Wood give a lecture on stratospheric sulfur dioxide at a 1998 climate conference in Aspen. But being a scientist who prefers data to dogma—even if the environmental dogma in this case lay close to his heart—Caldeira ran a climate model to test Wood’s claims. “The intent,” he says, “was to put an end to all the geoengineering talk.”
He failed. As much as Caldeira disliked the concept, his model backed up Wood’s claims that geoengineering could stabilize the climate even in the face of a large spike in atmospheric carbon dioxide, and he wrote a paper saying so. Caldeira, the most reluctant geoengineer imaginable, became a convert—willing, at least, to explore the idea.
Which is how it comes to pass that, more than ten years later, Caldeira, Wood, and Myhrvold—the onetime peacenik, the onetime weapons architect, and the onetime Viking fanboy—are huddled together in a former Harley-Davidson repair shop showing off their scheme to stop global warming.
It wasn’t just the cooling potential of stratospheric sulfur dioxide that surprised Caldeira. It was how little was needed to do the job: about thirty-four gallons per minute, not much more than the amount of water that comes out of a heavy-duty garden hose.
Warming is largely a polar phenomenon, which means that high-latitude areas are four times more sensitive to climate change than the equator. By IV’s estimations, 100,000 tons of sulfur dioxide per year would effectively reverse warming in the high Arctic and reduce it in much of the Northern Hemisphere.
That may sound like a lot but, relatively speaking, it is a smidge. At least 200 million tons of sulfur dioxide already go into the atmosphere each year, roughly 25 percent from volcanoes, 25 percent from human sources like motor vehicles and coal-fired power plants, and the rest from other natural sources like sea spray.
So all that would be needed to produce a globe-changing effect is one-twentieth of 1 percent of current sulfur emissions, simply relocated to a higher point in the sky. How can this be? Myhrvold’s answer: “Leverage!”
Leverage is the secret ingredient that distinguishes physics from, say, chemistry. Think back to the Salter Sink, IV’s device for preventing hurricanes. Hurricanes are destructive because they gather up the thermal energy in the ocean’s surface and convert it into physical force, a primordial act of leverage creation. The Salter Sink ruptures that process by using wave power to continually sink the warm water all through hurricane season.
“A kilogram of sulfur dioxide, emitted by a truck or a bus or a power plant into the troposphere, does much less good for you than in the stratosphere,” Myhrvold says. “So you get a huge leverage, and that’s a pretty cool thing. That’s why Archimedes said, ‘If you give me a fulcrum, I can move the world.’”*
So once you eliminate the moralism and the angst, the task of reversing global warming boils down to a straightforward engineering problem: how to get thirty-four gallons per minute of sulfur dioxide into the stratosphere?
The answer: a very long hose.
That’s what IV calls this project—a “garden hose to the sky.” Or, when they’re feeling slightly more technical, a “stratospheric shield for climate stabilization.” Considering its scientific forebear and the way it wraps the planet in a protective layer, perhaps it should be called Budyko’s Blanket.
For anyone who loves cheap and simple solutions, things don’t get much better. Here’s how it works. At a base station, sulfur would be burned into sulfur dioxide and then liquefied.