Countering global warming with cooling 

In your recent column on conspiracy theories about the government injecting chemicals into the atmosphere, you disparaged the idea of geoengineering, or at least using sulfur dioxide to counter global warming. But you don't defend your position. Is it a good or bad idea, and why? - Rob

The basic idea is simple. Our problem is global warming, right? We know when volcanic eruptions blast vast quantities of sulfur dioxide into the atmosphere, the pollution blocks sunlight and the earth noticeably cools off. Therefore, if we create artificial volcanoes to pump sulfur dioxide or other substances into the air, the resultant cooling will cancel out warming and we can go on happily burning fossil fuels and generally making a mess of the environment just like before.

Even in summary you can glimpse the dubiousness of this scheme, and the more you dig into it the worse it sounds. The core issue is this: Although everybody calls what's happening global warming, the more precise term is "anthropogenic global climate change"-a critical difference. While increased greenhouse gases are expected to lead to a warmer environment overall, that's just on average. Some areas will get wetter and some dryer. Many will get hotter; a few will get cooler.

Not to be parochial, but your columnist, who lives in Chicago, analyzed weather service data a couple years ago and found average late-spring temperatures in northern Illinois, hardly tropical to start with, have gotten noticeably cooler over the past 60 years. Is that due to human-caused climate change?

I have no idea, but I do know the 1991 eruption of Mount Pinatubo in the Philippines was followed by cooler summers in the midwest, which climatologists attribute to blocked sunlight. If we start heaving volcanic gases aloft on a regular basis, that doesn't just mean fewer days at the water park; we take the chance of screwing up the weather in a leading agricultural region.

That brings me to my larger point: Even if you can get past the idea of fighting pollution with pollution, we'd be fooling with a complicated system we don't fully understand. I'm not the only one to be alarmed about this. In 2008 Rutgers meteorology professor Alan Robock contributed a piece to the Bulletin of the Atomic Scientists called "20 Reasons Why Geoengineering May Be a Bad Idea." Among his concerns:

Effects on regional climate. Essentially what I said above. Robock points out that while volcanic eruptions may have brought about some global cooling, they've also led to disastrous reductions in rainfall. "At the fall 2007 American Geophysical Union meeting, researchers presented preliminary findings from several different climate models that simulated geoengineering schemes and found that they reduced precipitation over wide regions, condemning hundreds of millions of people to drought."

Ozone depletion. More pollutants in the upper atmosphere will lead to the destruction of more ozone and thus to more dangerous UV radiation.

Less sun for solar power. Geoengineering could make the earth not only cooler but darker, reducing the output of the solar power systems. "Following the eruption of Mount Pinatubo and the 1982 eruption of El Chichón in Mexico," Robock reports, "scientists observed a direct solar radiation decrease of 25-35 percent."

Environmental impacts of implementation. Proposals for getting all that sulfur dioxide up there involve huge amounts of airplane exhaust, 12-mile-long hoses dangling from immense balloons, and 16-inch naval guns shooting one-ton shells of dust up in the air. Even if these nutty measures worked, you can imagine the side effects.

Wild as geoengineering sounds, it's attracted a surprising level of interest among scientists. You may say: What's the harm in studying these things? Surely no one would actually launch such a project without thinking through the possible consequences. Maybe so, but that's what they said about the war in Iraq. cs




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Cecil Adams

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