"Martin Rowley" wrote in
message ...

... the 1980 event ejected material into the stratosphere, but the
primary thrust of the explosion was horizontal rather than vertical,
and if I understand the data correctly, the stratospheric loading from
that was minimal. As you say, whether this one would do something
different will be interesting to say the least. 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.

Just to follow up on this.... these higher latitude events can have
*regional* / local effects of course - here a note I have of the Laki
event with dates given:

1783/84: Icelandic volcanic eruption (Laki): Primary eruptions (five)
from June 8th to July 8th, 1783(60% of the total volume of ejection),
but minor eruptions occurred until early February, 1784. A major event,
with huge production of sulphur & acid products. The majority of
emissions are thought to have been confined to the troposphere, but the
initial ejections of each of the five major events did penetrate the
tropopause into the stratosphere. The intense period of eruption tallied
with contemporary reports across Europe of a blue haze or dry-fog in the
atmosphere, damage to vegetation and occurrence of respiratory problems.
These effects are consistent with increased atmospheric loading of acid
aerosols, particularly sulphates.

Because of the lack of major stratospheric impact, there is controversy
surrounding this event: For Iceland itself, the following winter
(1783/84) was known as the 'Famine Winter': 25% of the population died.
However, did it really cause changes to the regional/European climate in
the years 1783, 1784 etc?



Martin.