Climate Controls

If we treated global warming as a technical problem instead of a moral outrage, we could cool the world.

Gregory Benford from the November 1997 issue

(Page 3 of 5)

First proposed by Martin in 1988, the "Geritol solution" of adding iron to the ocean had a rocky history. Many derided it automatically as foolish, arrogant, and politically risky. But in 1996 the idea finally got tested by the U.S. government, and it performed well. Near the Galapagos Islands lies a fairly biologically barren area. Over 28 square miles of blue sea, scientists poured 990 pounds of iron during a week of testing. Immediately the waters bloomed with tiny phytoplankton, which finally covered 200 square miles, suddenly green. Plankton production peaked nine days after the experiment started. One thousand pounds of iron dust stimulated over 2,000 times its own weight in plant growth, far greater than the performance of any fertilizer on land. The plankton soaked up carbon dioxide, reducing its concentration in nearby sea water by 15 percent. It quickly made up this deficiency by drawing carbon dioxide from the air.

Projections show that since this process would affect only about 16 percent of the ocean area, a full-bore campaign to dump megatons of iron into the polar oceans probably would suck somewhere between 6 percent and 21 percent of the carbon dioxide from the atmosphere, with most recent estimates settling around 10 percent. Such scary, big-time tinkering is the extreme; the method would have to be tested at far lower levels. Still, this mitigation could dent the greenhouse problem, though not solve it entirely.

Even such partial solutions attract firm opponents. Geoengineering carries the strong scent of hubris. What is best described as eco-virtue reared its head immediately after the 1988 proposal, even before any experiments took place. Following the Puritan model that any deviation from abstinence is itself a further indulgence, many scientists and ecologists saw in Martin's plan an incentive for polluters. "A lot of us have an automatic horror at the thought," commented atmospheric authority Ralph Cicerone of the University of California at Irvine.

Other specialists retaliated. Russell Seitz of Harvard said the Galapagos experimenters were afraid to seem politically incorrect. "If this approach proves to be environmentally benign," Seitz said, "it would appear to be highly economic relative to a Luddite program of declaring war against fire globally."

Large uncertainties remain: How would the iron affect the deeper ecosystems, of which we know little? Will the carbon truly end up on the seabed? Can the polar oceans carry the absorbed carbon away fast enough to not block the process? Would the added plankton stimulate fish and whale numbers in the great Antarctic Ocean? Or would some side effect damage the entire food pyramid? Even if the idea worked, who should run such a program? Additionally, there is some evidence that little of the newly fixed carbon in the Galapagos experiment actually sank.
It seems to have come back into chemical equilibrium with the air. Controversy surrounds this essential point; clearly, here is where more research could tell us much.

This much seems certain (and should allay many fears): If we decide to stop the Geritol solution because of unforeseen side effects, control is easy. The standing crop will die off within a week, providing a quick correction.

Costs, too, are easy to figure. There is nothing very high-tech about dumping iron. Martin estimated that the job would take about half a million tons per year. Depending on what sort of iron proves best at prodding plankton, and implementation methods, the iron costs range between $10 million and $1 billion a year. Throwing in 15 ships steaming across the polar oceans all year long, dumping iron dust in lanes, brings the total to around $10 billion. This would soak up about a third of our global fossil-fuel-generated carbon dioxide emissions each year.

Reflecting on Reflectivity

Not all mitigation efforts need take place on land or sea. In fact, the most intuitive approach may be simply to reflect more sunlight back into space, before it can be emitted in heat radiation and then absorbed by carbon dioxide. People understand the basic concept readily enough: Black T-shirts are warmer in summer than white ones. We already know that simply painting buildings white makes them cooler. We could compensate for the effect of all greenhouse gas emissions since the Industrial Revolution by reflecting less than 1 percent more of the sunlight.

A mere 0.5 percent change in Earth's net reflectivity, or albedo, would solve the greenhouse problem completely. The big problem is the oceans, which comprise about 70 percent of our surface area and absorb more light because they are darker than land.

When it comes to increasing albedo, it would be wise to begin the discussion by introducing positive measures that can be easily understood and are close at hand. Reflecting sunlight is not a deep technical idea, after all. Simply adding sand or glass to ordinary asphalt ("glassphalt") doubles its albedo. This is one mitigation measure everyone could see--a clean, passive way to Do Something.

A 1997 UCLA study showed that Los Angeles is 5 degrees Fahrenheit warmer than the surrounding areas, mostly due to dark roofs and asphalt. Cars and power plants contribute, but only a bit; at high noon, the sun delivers to each square mile the power equivalent of a billion-watt electrical plant.

This urban "heat island" effect is common. But white roofs, concrete-colored pavements, and about $10 billion in new shade trees could cool the city below the countryside, cutting air conditioning costs by 18 percent. Cooler roads lessen tire erosion, too. About 1 percent of the United States is covered by human constructions, mostly paving, suggesting that we may already control enough of the land to get at the job.

From such homegrown solutions, we could make the leap to space. The most environmentally benign proposal for increasing the planet's albedo is very high-tech (and expensive): a massive orbiting white screen, about 2,000 kilometers on a side. Even if such parasols were broken into small pieces, putting them up would cost about $120 billion, a bit steep. We would also have to pay a lot to take them down if they caused some undesirable side effects. (One is certain: a night sky permanently light-polluted, irritating astronomers and moonstruck lovers.)

Using more-innocuous dust to reflect sunlight does not work; it drifts away, driven off by the sun's light pressure. But the upper atmosphere is still a good place to intervene, because much sunlight gets absorbed in the atmosphere on its way to us. Also, measures far above our heads trouble us less.