http://www.erh.noaa.gov/car/Newsletter/htm_format_articles/climate_corner/yearwithoutsummer_lf.htm
More like Decade without Summer if Yellowstone blows!
It’s unlikely we will see a super-eruption in our lifetimes, but there has been increased seismic activity in the park in recent years, starting with a large swarm in January 2009.
That suggests that we may well see some very scary event like a hydrothermal explosion or even a smaller eruption in our lifetimes.
There’s a lot of scary stuff that can happen at Yellowstone short of a super-eruption. I follow this fairly closely since it will be my rear end if it goes off, and the September swarm definitely got my attention.