I just typed a bunch of random letters, it just so happened to spell the name of that Icelandic volcano that is erupting like a mother as we speak. The "islandmountainglacier volcano" has been spewing for a day shy of a week and it has been hampering travel plans worldwide. But what sort of impact is it having on a climatic scale?
Despite the wide spread impacts, this volcano is not really going to have a long-term impact on the climatologyy of the world. In the past, large eruptions have altered global temperatures by 1-2 degrees Celsius. While this is a pretty good sized eruption, its composition is not one that would alter global temperatures. Take a look at the picture to the left, you can see the grey stream of ash that is pointed like a fire hose to Europe. Many eruptions have Sulfur Dioxide comprised in them and the sulfur acts as a reflecting agent that sends incoming solar radiation from the sun back into space. Large scale eruptions (Vesuvius, St. Helens, Santorini, Etna) spew great amounts of this sulfur dioxide into the atmosphere. That tends to linger and gets dispersed by the global winds and results in the lowering of global temperatures. But Eyjafallajokull is not emitting that much dioxide, so scientists are not expecting any climatic impacts from this eruption. Clearly there will be smaller scale impacts but they will not linger as long as a world wide impact could.
One of those small scale repercussions are thunderstorms. The heat released by the volcano mixes with cold air as well as ice particles colliding cause electrical discharges that result in these awesome lightning displays. These are often refered to as "dirty thunderstorms".