April 17, 2010

Iceland Eruption Too Small To Cool The Planet

In the past, volcanic eruptions have had a cooling effect on the Earth's climate, but the recent Icelandic eruption is too small to provide any relief from manmade global warming, scientists said on Friday.

The biggest cooling event of the last 30 years was the 1991 eruption of Mount Pinatubo, which cooled the Earth's surface by nearly 1 degree Fahrenheit over the following year. This, in turn, was enough to offset the impact of greenhouse gases from 1991 to 1993.

The Mount St. Helens eruption in 1980 triggered a smaller cooling event. That episode, though impressive in its own right, only released one-tenth of the material of Pinatubo.

The cooling comes from a simple formula: The volcano unleashes large amounts of fine volcanic ash and sulfur dioxide, which are released into the upper atmosphere -- the stratosphere. Once there, a process creates a fine layer of whitish particles that blow around the Earth for months or years and reflect some of the Sun's heat back into space rather than letting it reach the ground.

Thus far, the Icelandic event has been too small for such a cooling to occur. In addition, the eruption has not contained a sufficient amount of sulfur, and the plume circulated at too low an altitude to make an impact.

Any effect that the ash cloud has will be "very insignificant," said Scylla Sillayo of the World Meteorological Organization (WMO) in Geneva.

At its current level, the eruption is 100 times smaller than Mount St. Helens.

"At the scale it's at now, it's relatively unlikely that it will have any perceptible effect on climate," explained Kathryn Goodenough of the British Geological Survey (BGS).

The Mount Pinatubo eruption set off an ash cloud that reached 58,000 feet into sky. The Iceland eruption has only managed to send the plume an average of 20,000 feet up, with a few peaks at 35,000 feet. In these ranges, powerful winds have a huge dispersing effect.

The Eyjafjallajokull eruption in Iceland could have a regional effect on Europe's climate, but only if the eruption lasted for months or years.

There is a theory that the present eruption could touch off a much bigger eruption from the neighboring Katla volcano. While only a theory right now, it did happen in in 1823. After the periodic eruptions of Eyjafjallajokull from 1821 to 1823, Katla erupted.

Though people speculate there is a link between the two volcanoes through fissures, "it is important to emphasize there is no proof the one would trigger the other," Goodenough said.

In any event, volcanic cooling is only a temporary solution to the effects of manmade greenhouse gases, which are blamed for altering Earth's fragile climate system.


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British Geological Survey