NASA - Goddard Institute for Space Studies Research News:
Volcanic Blast Location Influences Climate Reaction

Mount Katmai erupted on June 6, 1912. Ash devastated areas hundreds of
miles away. That eruption is said to have cooled the Northern
Hemisphere during the summer, weakened the Asian monsoon, warmed India,
and cooled Asia the following winter. Temperatures around the world
dropped by 1-2 degrees Fahrenheit up to two years following the
eruption.

A study based on that eruption concluded that eruptions to the far
north of the equator have a different affect on the world's climate to
volcanoes in the tropics. There is less cloud cover, warmer
temperatures and less precipitation across northern India west into the
Persian Gulf.

Studies on tropical volcanic eruptions show a change in the, an
anticlockwise winds pattern circling the Arctic at about 55 degrees
north. (Spinning slowly it sends cold air down toward the equator into
the mid-latitudes, a faster spin keeps the cold up north.)

Aerosols from Mount Pinatubo's eruption on 12th June 1991, spread
around the globe in the troposphere and allegedly blocked the sun,
cooling the tropics. It is further alleged that this reduces the north
to south temperature difference that helps to shift the Arctic
Oscillation, keeping frigid air in the north during the winter,
resulting in mild conditions over much of eastern North America.

But, when Alaska's Mount Katmai erupted, most of the aerosols
remained well to the north, where they were not heated as much. In
turn, the lower stratosphere did not warm greatly, so there was little
influence on the Arctic Oscillation.

http://pubs.giss.nasa.gov/abstracts/...manRobock.html

http://www.nasa.gov/vision/earth/env...o_climate.html
The study appeared in the July 2005 issue of the Journal of Geophysical
Research-Atmospheres.

These are the snags I came up with:
The angle that insolation hits the aerosols in the northern hemisphere
will -in summer (as with the Katmai eruption) heat the pollution more
than that
which appeared with the Pinatubo eruption. The angle of incidence is
such that more radiation will get under the aerosols and of course with
the increased length of the day, do so for longer.

Then there is the fact that glaciers can exist in the tropics despite
their height and thus increased exposure to insolation. (From their
existence by the way it aught to be pretty clear that insolation is not
he be all and end all of meteorology that logic would suggest.)

Assuming that the aerosols have different affects at different
latitudes is another way of saying that aerosols don't have the
effect that they are or were assumed to have. In fact you could say
that the temperature differences might well have been caused by another
effect altogether.