Environmental Engineering Reference
In-Depth Information
(a)
(b)
Figure 13.3 Aerosol
climate model simulation of a decade-long Roza-scale
eruption (releasing 1200 Tg of SO
2
per year) with (a) showing the annual mean
change in aerosol optical depth (AOD) at 550 nm for the tenth year of the eruption
with respect to a pre-industrial control simulation, and (b) showing the latitudinal
mean AOD for a pre-industrial control simulation (dashed) and the volcanically
perturbed simulation (solid). The latitude of the eruption is indicated by the black
triangle.
-
carbon isotope excursions at the end-Permian, rather than these excursions being
due to the release of volcanic carbon (Wignall,
2001
, and references therein).
For the 14.7 Ma decade-long Roza
flow, Thordarson and Self (
1996
) estimated a
change in aerosol optical depth (AOD) at 550 nm of between 7 and 13, which is at
least 2.5 times larger than that for Toba (peak AOD of 2.6;
English et al
.,
2013
).
However, Thordarson and Self (
1996
) assumed that all SO
2
released is converted
to sulfuric acid aerosol of a certain size. Accounting for oxidant availability and
microphysical processes in a global model simulation of a Roza-scale eruption,
A. Schmidt (unpublished data) found an annual mean AOD change of 1.2 when
averaged over the northern hemisphere (
Figure 13.3
), which is signi
cantly
lower than previously estimated but nonetheless would have resulted in a
substantial perturbation of climate if maintained for a decade. Since the climatic
perturbations are relatively short-lived on geological timescales, A. Schmidt
(unpublished data) suggested that better constraints on the frequency and dur-
ation of individual eruptions as well as non-eruptive phases are needed to fully
quantify the magnitude and duration of the climatic and environmental effects
(see also
Chapter 11
).
13.5.2 Post-2000 small- to moderate-sized eruptions (VEI 3
-
4)
The rate of global warming slowed between the years 2005 and 2012. Among other
contributing factors, VEI 3
-
4 volcanic eruptions during that period contributed a
