Attempts to manipulate climate to counteract current trends of global warming could cause more problems than they solve, a study of weather data suggests.

Major volcanic eruptions spew large amounts of tiny particles, or aerosols, high into the atmosphere, where they scatter light back to space and significantly cool Earth for months to years (SN: 2/18/06, p. 110). Some researchers have proposed deliberately lofting tons of tiny particles into the stratosphere to achieve the same effect. That's probably not a good idea, says Kevin E. Trenberth, a climatologist at the National Center for Atmospheric Research in Boulder, Colo.

Trenberth's team studied data gathered by weather stations and river gauges worldwide from 1950 to 2004. For the 16 months following the 1991 eruption of Mount Pinatubo in the Philippines—an event that temporarily cooled Earth as much as 0.3°C—daily precipitation over landmasses worldwide dropped, on average, about 0.07 millimeter. Although that sounds small, no other large-scale weather phenomenon during that period triggered an extended decrease in daily precipitation that exceeded 0.04 mm.

Because the current global warming trend results from an increase in the atmospheric concentration of carbon dioxide, not an increase in solar radiation, simply providing Earth some shade doesn't address the problem, the researchers say in the Aug. 16 Geophysical Research Letters. Besides causing extended droughts, lofting artificial aerosols could significantly affect weather patterns and ocean currents, the team cautions.

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