John Snyder’s column relating sulfur dioxide and volcanoes to climate change brings to my mind the subject of geoengineering.
When volcanoes erupt, they loft SO2 high into the atmosphere, where it's chemically converted into sulfate particles. The particles reduce the temperature on the earth’s surface by reflecting incoming solar radiation back to space. Volcanoes, as Snyder points out, are one source of SO2 and account for approximately 30 percent of total SO2 emissions in North America, according to Ozone Monitoring Instrument satellite measurements. The majority of SO2 emissions are from coal-fired power plants and smelters. Volcanoes account for less than 1 percent of carbon dioxide emissions, according to the U.S. Geological Survey.
Rather than praying to Pele, the Hawaiian goddess of volcanoes, for more eruptions, it has been proposed to inject SO2 directly into the earth’s stratosphere, where it will do the most good while helping to prevent health effects from pollution, acid rain and smog. These sulfates, which can linger in the atmosphere for a few years, are spread around the Earth by stratospheric winds. But while the injections would counter global warming, they would not address all problems associated with climate change, and they would have their own negative side effects.
For example, the injections would not offset ocean acidification, which is linked directly to CO2 emissions. The injections would need to continue indefinitely, or at least until mitigation efforts were sufficient to greatly reduce CO2 emissions, which is the only real long-term solution to climate change.