Environmental Engineering Reference
In-Depth Information
Figure 5.6
Mean anomalies of surface air temperature
(°C) for the period 2 to 3 years after volcanic
eruptions with volcanic explosivity power
approximately equal
to the Krakatoa eruption, (a) Winter (b) Summer.
Points show the stations used. Dashed regions depict n
egative anomalies
produced a similar pattern, and Groisman
suggests that the unusually mild winter of 1991-
92 in central Russia was an indication of a
positive anomaly associated with Mount
Pinatubo. The warming is seen as a result of the
greater frequency of westerly winds over Europe,
which owe their development to an increase in
zonal temperature gradients following the general
global cooling associated with major volcanic
eruptions.
Volcanoes have the ability to contribute to
changes in weather and climate at a variety of
temporal and spatial scales. At a time when the
human input into global environmental change
is being emphasized, it is important not to ignore
the contribution of physical processes, such as
volcanic activity, which have the ability to
augment or diminish the effects of the
anthropogenic disruption of the earth/
atmosphere system.
THE HUMAN CONTRIBUTION TO
ATMOSPHERIC TURBIDITY
The volume of particulate matter produced by
human activities cannot match the quantities
emitted naturally (see Figure 5.7). Estimates of
the human contribution to total global particulate
production vary from as low as 10 per cent (Bach
1979) to more than 15 per cent (Lockwood 1979)
with values tending to vary according to the size-
fractions included in the estimate. Human
activities may provide as much as 22 per cent of
the particulate matter finer than 5 µm, for
example (Peterson and Junge 1971). It might be
expected that the human contribution to
atmospheric turbidity would come mainly from
industrial activity in the developed nations of the
northern hemisphere, and that was undoubtedly
the case in the past, but data from some
industrialized nations indicate that emissions of
particulate matter declined in the 1980s (see
Figure 5.8). There is also some evidence that the
burning of tropical grasslands is an important
source of aerosols (Bach 1976), and although
specific volumes are difficult to estimate, smoke
and soot released during the burning of tropical
Source:
From Groisman (1992)
Groisman (1992) has compared temperature
records in Europe and the northeastern United
States with major volcanic eruptions between
1815 and 1963. The results show that in western
Europe, and as far east as central Russia and
Ukraine, statistically significant positive
temperature anomalies occur in the winter
months some 2 to 3 years after an eruption the
size of Krakatoa (see Figure 5.6). The analysis of
data following the eruption of El Chichón
