Can we test our geoengineering schemes before we have to use them?

News and commentary about environmental issues.
Jan. 28 2010 5:53 PM

The Earth Trials

Can we test our geoengineering schemes before we have to use them?

Mount Pinatubo erupting in 1991. Click image to expand.
Mount Pinatubo erupting in 1991

The Copenhagen climate meeting was a big disappointment. Sen. Lindsey Graham now says the cap-and-trade bills "are going nowhere." So despite continued work toward cutting greenhouse emissions, we may see in the coming months a renewed interest in geoengineering—the deliberate, large-scale manipulation of the atmosphere—in an attempt to ward off the dangers of climate change.

The once-rogue concept of planet-hacking has come a long way in just three years: from key private meetings among scientists, to sophisticated computer modeling papers (PDF), to serious investigations of the idea by the British Royal Society and the U.S. National Academy of Sciences. This week the discussion moves into a new phase: a debate over how actual field tests for geoengineering should be implemented, regulated and, in fact, whether their results would even help us to understand the most severe risks of deployment at all. In three opinion pieces published in the premiere science journals—one in Nature yesterday, and two in Science today—scientists from across the world offered differing takes on the future of internationally coordinated testing. But their back-and-forth over which experiments might be best and what sort of political treaties would be necessary raises a distressing possibility: It's not just that geoengineering tests will be difficult. It's that the problems they invite would be so diverse—and their results so inconclusive—that we're likely to skip the testing altogether. If countries are going to hack the stratosphere, they may just do it full-bore in the face of disaster.

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The three papers naturally focus on what's considered the fastest and most feasible form of geoengineering—the sun-blocking method some call the Pinatubo Option. If deployed, this would mimic the cooling effect of volcanoes by putting a cloud of particles in the upper atmosphere, where they could scatter a small percentage of the sun's rays. (It's named after the eruption of Mount Pinatubo in 1991. That event cooled the globe 1 degree Farenheit in less than a year by spewing 10 million tons of sulfur pollution into the stratosphere.) Scientists have proposed creating a cloud of sulfuric acid or other particles using airplanes, naval guns, or hoses suspended by balloons. So, can we do a practice run of the Pinatubo Option?

The easiest experiments would involve the design of geoengineering hardware and tools to monitor the dispersal of particles from the ground. We might be able to look at how very small particle clouds affect local ozone levels or weather conditions at low altitudes. Those small-scale tests aren't likely to affect the climate at all, but they wouldn't give us very much information on the gravest risks of geoengineering, either. A more useful set of tests would be medium-scale field applications of the Pinatubo Option—in the form of releasing particles into the sky for years, enough time to alter the climate. In theory, this might help us to understand how dimming the globe effectively might shift circulation patterns or perturb the stratospheric ozone layer. But that's where things get dicey, according to University of Calgary physicist David Keith and colleagues writing in Nature. The trick is to balance usefulness with risk in experiments. Some compare (PDF) the ideal field-testing regime for the Pinatubo Option to a clinical trial for a new pharmaceutical drug, in which scientists incrementally trade higher risks for more useful data. They start with mice and increase the dosage in the trial gradually, with each step mitigating the dangers of the next one. The larger doses may have more side effects, but they also yield more information about the drug when taken at full strength.

Keith advocates such an approach for geoengineering, calling for "a carefully designed, incremental, transparent and international program" of sun-blocking approaches like the Pinatubo Option. "It would be reckless to conduct the first large-scale [sun-blocking] tests in an emergency," he writes. "Experiments should expand gradually to produce barely detectable climate effects and reveal unexpected problems, yet small enough … to limit risks." But he acknowledges that even an experiment involving one-tenth the sulfur of Pinatubo would involve "nontrivial" dangers.

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