Geoscience Reference
In-Depth Information
(A)
1883 (Aug-Nov)
60°N
30 NOV
40°
31 OCT
10 OCT
31 OCT
10 OCT
22 SEPT
22 SEPT
20°
0°
20°
22 SEPT
40°
10 OCT
60°
180°
120°
60°W
0°
60°E
120°
180°
(B)
1
98
2 (April)
40°N
20°
0°
20°S
0°
60°E
120°
180°
120°
60°W
0°
Figure 2.12
The spread of volcanic material in the atmosphere following major eruptions: A Approximate
distributions of observed optical sky phenomena associated with the spread of Krakatoa volcanic dust
between the eruption of 26 August and 30 November 1883. B The spread of the volcanic dust cloud
following the main eruption of the El Chichón volcano in Mexico on 3 April 1982. Distributions on 5, 15 and
25 April are shown.
Sources: Russell and Archibald (1888), Simkin and Fiske (1983), Rampino and Self (1984), Robock and Matson (1983). A: by
permission Smithsonian Institution.
in less than three weeks. The spread of the
Krakatoa dust in 1883 was more rapid and
extensive due to the greater amount of fine
dust that was blasted into the stratosphere. In
June 1991, the eruption of Mount Pinatubo in
the Philippines injected 20 megatons of SO
2
into the stratosphere. However, only about
twelve eruptions have produced measurable
dust veils in the past 120 years. They occurred
mainly between 1883 and 1912, and 1982 and
1992.
Volcanic eruptions, which inject dust and
sulfur dioxide high into the stratosphere,
are known to cause a small deficit in surface
heating with a global effect of -0.1
C,
but the effect is short-lived, lasting only a year
or so after the event (see
Box 13.1
). In addition,
unless the eruption is in low latitudes, the dust
and sulfate aerosols remain in one hemisphere
and do not cross the equator.
The contribution of man-made particles
(particularly sulfates and mineral dust) has
been progressively increasing, and now
accounts for about 30 percent of the total
tropospheric aerosol load. Sulfate emissions
have decreased in Europe and North America
since the 1990s, but increased in southern and
eastern Asia; global sulfate emissions have
°
to -0.2
°
