There have been some spectacular videos and photos of the latest volcanic eruption to occur: Calbuco in southern Chile. Climatologists have been watching the eruption closely to see what climate impacts, if any, will occur due to the eruption.
Big volcanic eruptions are known to shoot sulfuric acid high into the atmosphere where it forms little shiny droplets that reflect sunlight back to space before it can warm up the earth’s surface. I’ve discussed it in this blog before, and there is also a good explanation in this blog entry at http://www.carbonbrief.org/blog/2015/04/how-do-volcanic-eruptions-influence-the-climate/. Note that the more visible ash that is pulverized rock does not usually get up as high as the sulfuric acid and is too heavy to stay aloft for long, so it generally only causes local effects.
It is really too early at this point to determine how much sulfuric acid got up into the stratosphere, so we won’t be able to tell how much cooling the eruption might cause. If any does occur, it is likely to affect mainly the Southern Hemisphere because it will take time (several months at a minimum) for the sulfuric acid aerosols to move north and cross the equator, and while they are migrating they are also falling out of the stratosphere and so become less effective at reflecting sunlight.