It's still to early in the eruption process so far to say exactly what the long term effects the eruption of Iceland's Eyjafjallajokull Volcano will be. But so far the eruption appears to be small enough to be sub-climatic in scale.
The prevailing westerly winds are driving the ash plume over Europe. The plume is big enough to be visible from space by weather satellites.
According to experts at the USGS, the volcano is capable of producing only regional effects so far. Unless the eruption gets much bigger, things may stay that way.
Here are some observations about the eruption at this point.
-Reports indicate the ash plume is ejecting material between 18,000 and 36,000 feet into the atmosphere. This is what's causing havoc with air traffic in Europe.
-So far there is not enough material being ejected into the atmosphere to cause climatic scale impacts.
-Reports and measurements indicate the glacial melt is effectively "scrubbing" some of the Sulphur Dioxide (SO2) out of the volcanic plume before it can reach the atmosphere. SO2 is the most effective gas when it comes to reflecting incoming sunlight and causing potential climatic scale cooling.
-The plume consists of fine scale rock and glass particles. Most of these particles range in size between 1/12th and 1/250,000 of an inch. These tiny particles can stay suspended for months or years in the upper atmosphere.
This is a tiny eruption so far when compared historically to bigger volcanic events.
-Mt. Pinatubo's eruption in 1991 was rated a 6 on an eruption scale of 1 to 8. That eruption is credited with cooling the northern hemisphere 1 to 2 degrees Fahrenheit for 1 to 2 years.
-The gigantic Mt. Tambora eruption in 1815 is credited with causing the infamous "Year without a summer" in New England in 1816. Frost and snow in every month that summer caused widespread crop failures in the northeast United States.