Volcanic ash and climate
Sulphur particles from volcanic eruptions may affect the cloud cover, and cool down the climate.
Natural-color satellite image from of the explosive eruptions at Eyjafjallajökull Volcano. Picture: NASA, Robert Simmon, using ALI data from the EO-1 team
Despite of being difficult to spell and almost impossible to pronounce, the name Eyjafjallajökull has been on every European’s lips lately. It all culminated on 14 April, when magma started erupting from the crevasse which the previous eruption had ruptured on the volcano nearly a month earlier.
As the lava reached the glacial ice, the cold water from the melting ice chilled it quickly, causing it to fragment into very small particles of glass (silica) and ash, which were carried into the atmosphere along the eruption column.
Even though the volcanic ash cloud is not visible on the continent, the impacts of it were immediate. Air traffic around Europe came to a standstill. The flight restrictions have been eased lately, but the long term effects of the eruption remain to be seen.
Atmospheric physicist Ilona Riipinen is a member of My Camp Climate Change steering group. She explains how the ash particles affect the climate directly and indirectly.
Ash itself can scatter the solar radiation or create the same effect indirectly through clouds. Every cloud droplet is formed around an aerosol particle, and the concentration or capacity within these particles determine the type of the cloud. Volcanic activity releases sulfur particles into the atmosphere, and these particles are very efficient cloud condensation nuclei.
In other words volcanic eruptions emit a lot of particulate matter to the atmosphere, which scatters solar radiation and affects the cloud cover, and as the result the climate may become cooler. The more powerful the eruption is, the higher the particles drift, and if they end up as high as in the stratosphere, the effects on climate can last even for years.
According to Heikki Pohjola from Väisälä Group, the latest statistically significant volcanic activity was the eruption of Mount Pinatubo in Phillipines, 1991. The climate decreased by half a centigrade Celsius globally for several months. If the bigger volcano Katla, next to Eyjafjöll, erupts like it has done after Eyjafjöll’s previous eruptions, the long term consequences might be similar to those after Pinatubo’s eruption.
The Finnish Meteorological Institute offer computed estimates on the transport of the ash cloud that are done using the Meteorological Institute’s dispersion model (SILAM). The forecast can be found from The Finnish Meteorological Institute’s website.
Link: The Finnish Meteorological Institute
Elisa Lautala works as web editor for University of Helsinki's Faculty of Science. Elisa likes all kinds of cultural events, good books, warm weather, and aqua-jogging.