Sulfurous ocean gases condensing into tiny aerosol particles over the Southern Pacific may seem far removed from the halls of government power. But they have a direct bearing on multibillion-dollar decisions that governments are considering as they try to respond to public pressure to "do something" about possible global warming.
Aerosols are the great unknown in computer-based climate forecasts. While "greenhouse gases" such as carbon dioxide and methane trap outgoing heat and warm the lower atmosphere, aerosol particles scatter sunshine back into space and cool things down. Climate modelers have a fair idea how to simulate greenhouse warming using computers. But they know zip about simulating the climatic influence of aerosol particles, say researchers studying the effect.
That's why aerosol chemist Timothy Bates at the National Oceanic and Atmospheric Administration's lab in Seattle says he can't have "real strong confidence" in climate modeling today. Dr. Bates is one of hundreds of atmospheric chemists engaged in an intensive international program to learn to make more accurate climate models. Some of them presented early fruits of their research this week at the fall meeting of the American Geophysical Union. As Bates and several colleagues explained, understanding the aerosol effect is substantially more complicated than dealing with greenhouse warming. Many aerosol particles are formed by sulfur dioxide emissions from burning fossil fuel. Others form from sulfurous volcanic gases and natural emissions of dimethyl sulfide by microscopic marine organisms. Uneven aerosol distribution complicates climate simulation, explains oceanographer Barry Huebert, of the University of Hawaii in Honolulu. Greenhouse gases are relatively long-lived and spread throughout the atmosphere; their warming effects act globally. …