"John Hall" wrote in message
...
In article ,
Martin Rowley writes:
However, I wonder if Mt. St.Helens
is a bit far north for major long-lasting effects anyway: I understand
that to have world-wide impact, the event would need to be in the
tropical/sub-tropical belt? However, would be glad to be corrected if
anyone has got more on this.

ISTR HH Lamb saying that in "Climate, History and the Modern World."
--
Found this on the CRU site which might help .... they imply that for
*maximum* effect such activity should be at lower latitudes etc.

http://www.cru.uea.ac.uk/cru/info/volcano/

Martin.