 - January 14, 2005 Volcanic eruptions can release large amounts of sulfur gases, mainly sulfur dioxide and hydrogen sulfide, into the atmosphere. These gases react with atmospheric hydroxyls (water) to form acid aerosols. While suspended in the atmosphere, aerosols can limit the amount of direct solar radiation reaching Earth's surface and possibly cause global cooling. The extent of the cooling is directly controlled by the amount of sulfur released into the atmosphere during the eruption and only indirectly controlled by the magnitude of the eruption. To significantly affect the global climate, sulfur gases need to be injected into the stratosphere (~10-15 km high). If the volcanic plume does not reach the stratosphere, precipitation will remove the particles from the atmosphere quickly. Above the stratosphere the volcanic aerosols can remain for 2-3 years, long enough to affect the climate for a couple of seasons. Initially, scientists believed that volcanic ash suspended in the atmosphere could cause global cooling. As it turns out, volcanic ash settles out of the atmosphere relatively quickly (within a couple of months) and, therefore, cannot account for global climate variations. |