Not so good news for Europe

Get ready for decades of Icelandic fireworks - environment - 16 April 2010 - New Scientist

Volcanologists say the fireworks exploding from the Eyjafjallajökull volcano on Iceland, which is responsible for the ash cloud that is grounding all commercial flights across northern Europe, may become a familiar sight. Increased rumblings under Iceland over the past decade suggest that the area is entering a more active phase, with more eruptions and the potential for some very large bangs.

"Volcanic activity on Iceland appears to follow a periodicity of around 50 to 80 years. The increase in activity over the past 10 years suggests we might be entering a more active phase with more eruptions," says Thorvaldur Thordarson, an expert on Icelandic volcanoes at the University of Edinburgh, UK. By contrast, the latter half of the 20th century was unusually quiet.

As for the question of whether the current eruption could cause significant cooling: apparently, it's not thought big enough yet to do that.

Update: there's a lot more comparative detail on the size of the Iceland volcano (and why it is not close to be being a big climate influence) here.