In
the case of the 1991 Mt. Pinatubo eruption, the sulfate aerosol cloud resulted
in a
radiative forcing of about -0.5 W/m2, which lasted for a few
months. This coincided
with a global cooling on the order of a few tenths of degree C, which lasted
a year or so.
Other
historical volcanic eruptions are also associated with anomalies in the climate
record. The most noteworthy is the
enormous 1815 eruption of the Tambora
volcano. This is referred to as
the Òyear without a summerÓ in Europe and
North America. The cooling effect
was probably on the order of 5¼C.
However,
the global cooling effects of the volcanic eruptions we are familiar with last
at most a few years.