Volcano makes sense, but i'm sure the size, how high the ash cloud rises, the type of particles, the weather at the time, latitude of the volcanon, elevation, etc probably all play into it...of course if Yellowstone blows, we can all kids our butts goodbye
Personally, if last summer is what summer is going to be like, give me another volcano. That was horrible...
I've always said, i'd rather have a record cold summer then a record cold winter!