Couple of points to mention; the Eyjafjallajokull volcano is at a high latitude in the Northern Hemisphere..volcanoes located in Iceland can a much higher impact on the weather than volcanoes in the tropics as a number of stuides have shown. (Some studies have shown just the opposite..as might be expected-different locations around the World are affected different based on the location of the volcano.) Having said that, this particular volcano doesn't have much sulfur in it and isn't generally producing much emissions above 30,000 feet which is the critical threshold for having climate effects.
More importantly, the melting of the glacier and removing all that weight from the summit of the nearby Katla caldera may cause that volcano to erupt sometime in the next year or so. (This scenario has happened several times before.)
That volcano is huge and has a much much higher chance of altering the World's climate.
"When Katla went off in the 1700s, the USA suffered a very cold winter," says Gary Hufford, a scientist with the Alaska Region of the
National Weather Service. "The Mississippi River froze just north of New Orleans, and the East Coast, especially New England, had an extremely cold winter. Depending on a new eruption, Katla could cause some serious weather changes.""
Lots of interesting articles and realtime data can be found here:
http://www2.norvol.hi.is/page/ies_Eyjafjallajokull_eruption
