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.
Observed
global air temperature anomaly associated with the Mt. Pinatubo eruption in 1991. (from Ahrens, Meteorology Today)