You might not be able to pronounce "Eyjafjallajokull" but if you're in Europe, you're feeling the effects. Travel is shut down thanks to an ash cloud spreading over parts of western Europe. And by "shut down," I mean air space is closed. Don't know why flying in volcanic ash is a bad thing? Read this. Harrowing doesn't begin to describe that.
On the global warming front, volcanic eruptions have, in the past, dropped global temps for a limited time, as seen with Mt. Pinatubo in 1991. It'll be some time before we'll even be able to deduce if Eyjafjallajokull has any affect though. That's the thing with climate. It always takes time.