ArticlePDF Available

The Impact of Mount Pinatubo on World-Wide Temperatures

Authors:

Abstract and Figures

We monitor and model the effects on world-wide temperatures of the June 1991 volcanic eruption of Mount Pinatubo in the Philippines. Global mean air temperatures were reduced, by up to 0.5°C at the surface and 0.6°C in the troposphere, for some months in mid-1992, in approximate accord with model predictions. Differences from these predictions occurred in the Northern Hemisphere winters of 1991-1992 and 1992-1993, as a result of atmospheric circulation changes that yielded continental surface warmings not fully reproduced by the model. The effects of the eruption were less evident by 1994. A superposed-epoch composite for five major tropical eruptions shows significant global post-eruption cooling at the surface when the effects of the El Ni7o-Southern Oscillation are removed from the data. Stratospheric warmth following Pinatubo lasted until early 1993 according to Microwave Sounding Unit data.
Content may be subject to copyright.
INTERNATIONAL JOURNAL
OF
CLIMATOLOGY,
VOL.
16,487497
(1996)
THE IMPACT
OF
MOUNT PINATUBO ON WORLD-WIDE
TEMPERATURES
D.
E.
PARKER
Hadley Centre, Meteorological Ofice, London Road, Bmcknell RGI2 2SI:
UK
H.
WILSON
Columbia University and NASA, Goddard Institute for Space Shtdies, New York.
USA
I?
D. JONES
Climatic Research Unit, University
of
East Anglia,
UK
J.
R.
CHRISTY
Department of Atmospheric Science, University of Alabama
in
Hunlsville, Huntsville, Alabama. USA
AND
C.
K.
FOLLAND
Hadley Centreo Meteorological Ofice, London Road, Bracknell RG12 2SL
UK
Received I4 May
I995
Accepted
3
October
I995
ABSTRACT
We monitor and model the effects on world-wide temperatures of the June 1991 volcanic eruption of Mount Pinatubo in the
Philippines. Global mean air temperatures were reduced, by up to
0.5"C
at the surface and
0.6"C
in the troposphere, for some
months in mid-I 992, in approximate accord with model predictions. Differences from these predictions occurred in the Northern
Hemisphere winters of 1991-1992 and 1992-1 993, as a result of atmospheric circulation changes that yielded continental surface
warmings not
fully
reproduced by the model. The effects of the eruption were less evident by 1994.
A
superposed-epoch
composite for five major tropical eruptions shows significant global post-eruption cooling at the surface when the effects
of
the
El
Nifio-Southern Oscillation are removed from the
data.
Stratospheric warmth following Pinatubo lasted until early 1993 according
to Microwave Sounding Unit data.
KEY
WORDS:
volcanic eruptions; temperature variations; atmospheric circulation; Mount Pinatubo.
1.
INTRODUCTION
Many observational studies have been carried out to assess the climatic impacts
of
major volcanic eruptions. We do
not review these here, but refer readers to recent reviews by Mass and Portman (1989), Robock (1991) and
McCormick
et
al.
(1
995), and to the assessments made
in
the IPCC Reports (Folland
et
al.,
1990, section 7.2.1
;
Folland et al., 1992; Shine
et
al.,
1990). Most, but not all,
of
the studies reviewed find post-eruption surface cooling
of
several tenths "C on a world-wide average, despite difficulties encountered in making these assessments,
including the choice
of
radiatively effective eruptions, lack
of
statistical significance owing to small samples, and the
complicating influence
of
other atmospheric and oceanic variations such
as
the El Nifio-Southern Oscillation
(ENSO). Another widely recognized sequel to major eruptions is stratospheric warming (Parker and Brownscombe,
1983; Labitzke, 1994; McCormick
et
al.,
1995).
In this note we examine the changes of global surface temperature and tropospheric (Microwave Sounding Unit
(MSU)) air temperature observed since the June 199
1
eruption
of
Mount Pinatubo in the Philippines, in the light of
model predictions (Hansen
et
al.,
1992; Kolomeev
et
al.,
1993)
of
a global
or
hemispheric surface and tropospheric
cooling
of
about 0.5"C, at its strongest about a year
after
the eruption. We also use global average surface
temperatures around the times of Pinatubo and earlier eruptions to calculate superposed epoch global time series:
CCC 0899-8418/96/050487-11
0
Controller, HMSO, Norwich, England, 1996
488
D. E.
PARKER
ET
AL
these series are compensated for ENSO, using an index
of
the Southern Oscillation, to isolate the volcanic influence
more clearly.
An
influence of volcanic eruptions on Northern Hemisphere atmospheric circulation has already been discussed
by Robock and Mao (1992, 1995), Kirchner and Graf (1 995) and Graf
et al.
(1994), and is implied by the results of
Groisman (1 992). We examine this further with particular emphasis on Pinatubo.
Finally, MSU data are used to monitor stratospheric temperature changes following Pinatubo. The results are used
to conh both observational findings (Labitzke and McCormick, 1992; Labitzke, 1994) and modelling studies
(Graf
et al.,
1993; Kirchner and Graf, 1993). Linkages between the stratospheric temperature changes and those of
the Northern Hemisphere atmospheric circulation have already been proposed (Robock and Mao, 1992, 1995; Graf
et al.,
1993, 1994; Kirchner and Graf, 1993; Kelly
et al.,
1996): we briefly summarize their implications for the
analysis of volcanic effects.
2. RESULTS
2.1.
Changes
in
global surface temperature following Pinatubo
In Figure l(a) we show, in the solid curve, 3-month running mean global surface air temperature anomalies
following the June 1991 eruption of Pinatubo. Anomalies were calculated from a base-period 1961-1990, then
expressed relative
to
anomalies (not actual values) for the effectively pre-eruption 3-month period April to June
199
1.
Results relative to the 6-month period January to June 1991 and the 12-month period July 1990 to June 199
1
(not shown) were almost identical. The anomalies are based on land station air temperatures (Jones, 1994) and an
updated data base of the night-time marine air temperature (NMAT) measurements made fiom ships and buoys
described in Bottomley
et al.
(1 990). Day-time marine air temperatures were not used, because they are affected by
solar heating of ships' fabric. Air rather than sea-surface temperatures (SST) were used for compatibility with the
model results. A global cooling of about 0~5°C is observed between the eruption and the northern summer of 1992,
interrupted, however, by relative warmth between January and March 1992. Another period of relative warmth in
January to March 1993 was followed by a smaller cooling in the Northern Hemisphere summer of 1993. Early 1994
did not show a corresponding period of warmth, but a renewed warm period was seen in early 1995. If NMAT is
replaced by SST, the maximum observed cooling is reduced by about 0.1"C (not shown), owing to the greater
thermal inertia of the ocean.
Also included in Figure l(a) as dashed lines are corresponding global surface air temperature changes following
Pinatubo as predicted by the Goddard Institute for Space Studies (GISS) global coupled atmosphere-ocean climate
model (Hansen
et al.,
1988, 1992). This model has
8"
by 10" horizontal resolution, nine atmospheric layers, an
oceanic mixed layer with specified horizontal heat transports, and vertical diffusion to the deep ocean. The dashed
sequences in Figure l(a) were derived using randomly different initial atmospheric conditions for runs 'P1
'
and 'P2'
of the model
as
described by Hansen
et al.
(1 992). In both these
ms,
greenhouse gases increased linearly,
as
in
'scenario B'described in figure 2 of Hansen
et
al.
(1
988). The imposed aerosol burdens were also the same: the time-
dependence of global optical depth followed Hansen
et al,'s
(1 988) simulations of the effects of El Chichon, but with
an overall enhancement by a factor of 1.7, and with aerosols restricted uniformly to the belt 20"s to 30"N in the first
three months after the eruption, followed by a poleward spread into both hemispheres giving uniform cover in
January 1992. The implied net radiative forcings may, according to reanalysed aerosol data, be overestimated by up
to 20 per cent (Hansen
et al.,
1996). Also, the true aerosol distribution, although widespread, was not uniform by
January 1992 (Grant
et al.,
1994). Hitchman
et
al.
(1 994) present
a
climatology of stratospheric aerosol and show
that the combination of sporadic volcanic injections and stratospheric circulation is unlikely to result in a uniform
distribution in practice. Nonetheless, volcanic influences on global tropospheric temperature have been fitted well by
a simple exponential-decay formula
(Christy
and McNider, 1994), and, despite its shortcomings, the GISS model
simulates successfully the observed overall cooling, although it gives only weak indications of the temporary
warmings affecting the Northern Hemisphere winter.
Figure I@) shows that the observed temporary warmings took place almost entirely over land and were not
reproduced by the model, at least for Northern Hemisphere winter 1991-1992. The model also slightly under-
estimated the maximum cooling over land, but slightly overestimated the observed overall changes
of
global-ocean
The effect
of
the
Mt.
Pinatubo eruption, June
1991
M
M
(*ti*
to
Apd1-J~
1991)
1.0
-
Obscned
Land
Surface
Air
Temperahre
(rrl.ti~
to
April-J~~
1991)
0
--I--
MOadpreatc.rioaS
0..
-
V
f
03-
OJ-
-
*
0
0,
*
LI
$
0.0
-
4
45-
h-
h.
-
B
*
-1.0
4.6
08
“91
AM192
AMJ93
Am94
W9S
M96
AMJW
AMlI
AN91 AM192
AM193
AMJPI
AN95
AMJ%
AUJW
--
I-,
Modd
pmdkliws
-
-
-
-
...........I...).......1.1.../.....1....
s
0
0.4
fi
-
Observed
MSU
2R
(relalive
to
April-June
1991)
0.4
A
-
-
Obwed
Night
Marine
Air
Temperature
-
--
I--
Moddledloaertropospherepredlction
V
(dative
to
April-Joar
1991)
v-
--
I-
-
ModclprrdieW
-
m
0’:
-
0
2:
c-
8
P-
m
0.2
-
-
b
Figure 1. (a) Observed (solid line) and modelled (dashed lines) global surface land with night-time marine air temperatures following the eruption of Mount Pinatubo. Values are 3-month
nmaing
mean anomalies relative to the period April to June 1991, The series
run
from this period through to the period October to December 1995.
@)
As (a) but
for
land only. (c) As (a) but for
$
\o
ocean
only.
(d)
As
(a) but for the global lower troposphere. Observed are Microwave Sounding Unit (MSUZR)
data:
modelled are layer tempemtures, weighted to match MSUZR
TI
-
P
- -
490
D.
E.
PARKER
ET
AL.
surface air temperature (Figure l(c)). Global lower to middle tropospheric temperature changes (Figure l(d)) were
well simulated: cooling was slightly overestimated except in early 1993. See also section 2.3.
The reasons for the observed global surface warmth in the Northern Hemisphere winter of 1991-1992 are
apparent from the temperature and mean-sea-level pressure anomalies in Figures 2(a) and 3. Anomalies in these
fields are taken relative to the previous five Northern Hemisphere winters, for compatibility with superposed-epoch
analyses (see below) in which this was done to eliminate longer-term climatic changes. Sea-surface temperatures
(SSTs) are used in Figure 2(a) because they have better coverage than night-time marine air temperature, which
yielded noisier results. The SSTs came from the Global sea-Ice and Sea-Surface Temperature (GISST1.l) data set
with some unreliable Southern Ocean and Arctic SSTs deleted (Parker
et
al.,
1994). The procedure used to blend the
land air temperatures with the SSTs was simpler than that used by Parker
et al.
(1 994) because of the new grid-box
analysis of the land air temperatures (Jones, 1994), but data from small islands were still given enhanced weighting
relative to the proportion of land in their grid-box. Figure 2(a) shows that the enhanced warmth was concentrated
over northern Eurasia and over central North America (see also Halpert
et
al.,
1993)
as
a result of anomalies of
atmospheric circulation.
A
strong (1 1 hPa) anticyclonic mean-sea-level pressure anomaly centred over the British
Isles (Figure 3) resulted in the advection of warm air across Scandinavia: positive temperature anomalies further east
were ensured by the continued, albeit indirect, advection of some of this air, along with enhanced southerly flow in
central Asia. The enhanced warmth over North America was associated with northward advection east of a deeper
and eastward-displaced Aleutian low, relative to the previous 5-winter average (Figure 3). This circulation anomaly,
in
turn,
may have resulted from the El Niiio event then in progress, as evidenced by the anomalous warmth of the
central and eastern equatorial Pacific in Figure 2(a) and by the El Niiio-atmospheric circulation relationships
reviewed by Glantz
et
al.
(1 99 1). These results, along with the well known tropical warmth during El Niiio events
(Pan and Oort, 1983), suggest that compensation of observed series, such as those in Figure 1, for ENS0 (see also
Robock and Mao, 1992, 1995) may yield a clearer picture of the overall cooling influence of major volcanic
eruptions. We do this in an elementary way in section 2.2.
The GISS model, having generally only 1-2 layers in the stratosphere, may not simulate realistically the
dynamical interactions between the troposphere and stratosphere (Hansen
et al.,
1996) which appear to underlie the
observed atmospheric circulation changes in the Northern Hemisphere in winter following tropical eruptions (see
section 3).
So,
scenario ‘Ply (Hansen
et
al.,
1992) shows mixed winter surface temperature anomalies over Northern
Eurasia whereas ‘P2’ has anomalous warmth over central and eastern Siberia but greater coldness than observed in a
belt from Europe through central Asia to China.
Also, the GISS model cannot produce an El Niiio (Robock and Liu, 1994), because it has specified horizontal heat
transports in the oceanic mixed layer. Without this influence for winter warmth over central North America, the
model’s internal variability appears to have dominated the results there, with anomalous coldness
in
scenario ‘P1
(Hansen
et al.,
1992) but warmth in scenario ‘P2’,
in
the 1991-1992 Northern Hemisphere winter. Overall,
therefore, neither simulation fully reproduces the global-average warmth
in
this season. Furthermore, additional
simulations would, owing to internal variability, probably yield very disparate results on a regional scale, as would
additional volcanic eruptions of similar magnitude, location, and seasonal timing in the real world.
The model was in better agreement with observations regarding overall global coolness in the Northern
Hemisphere summer
of
1992 (Figure l(a)), when natural and modelled internal variability are smaller than in
winter. Observations (not shown) included strong cold anomalies (down to
-
3°C) over North America and central
northern Asia, and warm anomalies (up to
+
2°C) over Europe. The latter are not a consistent feature of post-
eruption summers (e.g. Groisman, 1992). The observed anomalies are consistent with anomalous advection by the
atmospheric circulation (not shown). There were also warm anomalies (up to
+
2°C) over the eastern North Pacific,
in connection with the El Niiio.
2.2.
Comparison with previous tropical eruptions
We chose Krakatau (August 1883), Pelee (May 1902), Soufiiere (May 1902) and Santa Maria (October 1902)
combined
as
a single event (October 1902), Agung (March 1963), and El Chich6n (April 1982). These eruptions are
associated with the largest estimated stratospheric aerosol optical depths (Sat0
et
al.,
1993). We restricted our
selection to the tropics, because Robock and Mao (1992, 1995) found that Northern Hemisphere winter warmth
MOUNT
PINATUBO
IMPACT ON TEMPERATURES
49
1
Surface tem erature anomalies
relative to average
of
DJF 198d7
-
1990/1
December 19
6
1
to Februar 1992
Figure 2. (a) Land-surface air and sea-surface temperatures, December 1991 to February 1992, relative to the average
for
the same season
of
the
previous
5
years. Isopleths every
0.5"C.
Negative values shaded.
(?J)
As
(a) but
MSUZR
data
for
the lower troposphere. lsopleths every 0.5T
with zero omitted. Negative contours dashed
492
D.
E.
PARKER
ET
AL.
Figure
3.
Northern Hemisphere mean-sea-level pressures, December 1991
to
February 1992, relative
to
the average for the same season of the
previous
5
years. lsopleths at
1
hPa intervals. Data source: blended analyses of the Meteorological Office, NCAR, and Scripps Institute of
Oceanography
tended to occur in the first winter after tropical eruptions, but in the second winter after higher-latitude eruptions., We
carried out a superposed-epoch analysis of monthly global land-surface air and sea-surface temperature anomalies
around the time of these eruptions and Pinatubo. Sea-surface temperatures were used because they have better
coverage than night marine air temperatures: global changes
of
these are expected to be very similar (Bottomley
et
al.,
1990). The anomalies were first referenced to the 5-year pre-eruption period, to remove the effects of longer term
climatic changes, and a low-pass smoothing filter, with half-power at
6
months period, was applied. The smoothed
anomalies were then composited; also standard errors were calculated from them (Figure 4(a)). Similar analyses
have been carried out by Kelly
er
al.
(1
996). The smoothed global temperature drop reached nearly 0.2"C about 15
months after the eruptions, effectively in the Northern Hemisphere summer ofthe post-eruption year. However, this
dips only marginally below
two
standard errors, largely because a major El Nifio, giving global warmth, followed the
eruption of El Chichon.
So
we then adjusted all the original monthly global surface temperatures for
ENS0
using
linear regressions against the standardized monthly Southern Oscillation index (Tahiti minus Darwin mean-sea-level
pressure: see Ropelewski and Jones (1987)) six months previously with a five-term binomial smoothing to eliminate
intraseasonal variations (Jones (1988); see also Robock and Mao (1992)). (Compensation for the Southern
Oscillation on a local basis, before taking global averages, was carried out by Robock and Mao (1995) and
could be more effective because geographically varying lags can be incorporated; but it could also yield noisy results
MOUNT PINATUBO IMPACT
ON
TEMPERATURES
493
in data-sparse areas and in regions where the ENSO signal is not dominant.) Then the composite coolness 15 months
after eruptions was close to 0.25"C (Figure 4@)) with reduced standard errors
so
that the statistical significance
reached the 99 per cent level, assuming five degrees of freedom in a one-tailed t-test, which is applicable given an a
priori expectation of cooling. The adjustment removed most of the warming following El Chichon. The adjusted
cooling following Pinatubo was comparable with, or a little greater than, that following most of the other eruptions
(Figure 4(c)). There was also significant cooling around 30 months after eruptions: because most of the eruptions
were in Northern Hemisphere spring, this was in the Northern Hemisphere autumn. Some of the remaining
variability between eruptions indicated by Figure
40,
and c) may have been caused by sparser data coverage around
the times of the earlier eruptions (Madden
et al.,
1993).
We have thus demonstrated consistency in overall cooling at the global surface after tropical eruptions. Next, we
examined a composite mean-sea-level pressure field (not compensated for the Southern Oscillation) for Northern
Hemisphere winters following the earlier eruptions. This field (not shown; covering an area similar to Figure 3)
indicates a strong similarity to Figure 3 over much of Eurasia: anomalous high pressure centred over France allowed
the advection of warm air across northern Europe towards central Asia. There was a weaker similarity over North
America and the Pacific, with a slightly deepened and eastward-displaced Aleutian low. The correlation with Figure
3, using 5" latitude
x
5" longitude grid-boxes, was
0.67
for the entire data area. Composite surface temperature
anomalies in the Northern Hemisphere winters following these four eruptions, not compensated for ENS0 (not
shown), were somewhat similar to Figure 2(a) (correlations 0.41, 0.34, 0.39
for
Northern Hemisphere, Southern
Hemisphere, globe), with warmth over northern Eurasia following all four eruptions and over North America
following Agung and El Chichon. There was also warmth over the central equatorial Pacific because the 1982-1 983
El Niiio was included in the composite.
As
after Pinatubo, this coincidence with El Nifio is likely to have contributed
to the anomalies in the mean-sea-level pressure field over the North Pacific and probably also therefore to the
temperature anomalies over North America (Glantz
et al.,
199 1).
2.3.
Changes
in
temperature
aloft
In Figure l(d) we present 3-month running mean global temperature anomalies for the lower to middle
troposphere based on 'MSU2R' radiances. These are most sensitive to temperatures near the
750
hPa level, with
substantial influence from the surface to 500 hPa but little sensitivity to temperature at 300 hPa (Spencer and
Christy, 1992). These MSU data indicate a global cooling of about 0.6"C between mid-1991 and mid-1992. This
was also noted by McCormick
et al.
(1 995). The pronounced temporary warmings
in
early 1992 and early 1993 at
the surface (Figure l(a)) were barely evident in the lower to middle troposphere (Figure I(d)). Tropospheric mid-
latitude continental winter temperature anomalies in general tend to be smaller than, although highly correlated with,
those at the surface, according to both the MSU (Spencer
et aE.,
1990) and radiosondes. Monthly averages of
radiosonde temperatures in the data base of Parker and Cox (1995) show a reduction of standard deviation
approaching 50 per cent between the surface and mid-troposphere in these regions in winter, and this decrease of
amplitude with height was evident in the winters of 1991-1992 and 1992-1993.
So
the weaker tropospheric
continental positive anomalies in these winters were more than compensated by negative anomalies in the subtropics
and the Arctic, especially in its North American sector (Figure 2(b)), giving negative global anomalies (Figure l(d)).
A similar balance occurred in March 1990, which was very warm at the surface over the Northern Hemisphere
(Parker and Jones, 1991). Note that this was not preceded by a tropical eruption (see section 3).
Figure 5 is a 17-year monthly temperature series for the global lower stratosphere, based on MSU Channel 4,
which monitors mainly the 150 hPa to
30
hPa layer, with peak sensitivity near
70
hPa (Spencer and Christy, 1993).
This series is dominated by the warmings following
El
Chichon (Parker and Brownscombe, 1983) and Pinatubo
(Labitzke and McCormick, 1992; Labitzke, 1994). These papers show that the major warmings occurred in the
tropics, where most, but not all (Trepte
et
al.,
1993) of the aerosol was concentrated in the first
4-6
months after the
eruptions, before its dispersal by synoptic-scale eddies and the meridional stratospheric circulation. When
El
Chichon erupted, the tropical stratospheric quasi-biennial oscillation (QBO) was in its warm phase (Labitzke and
McCormick, 1992) whereas the QBO was in its cold phase when Pinatubo erupted (Labitzke, 1994). This partially
explains the warmth before El Chich6n and coldness before Pinatubo in Figure 5 (Christy and Drouilhet, 1994). In
addition, the eruption of Cerro Hudson in Chile in August 1991 may have enhanced the post-Pinatubo warming
494
0.2
0
0.0
73
-0.2
D.
E. PARKER
ET
AL.
-
-
-
0.4:"
'
"
''
"
I'
"
"
''
"
~
0.2
I
-100
-50 0
50
100
Months before/cfter
eruption
0.41
'
' ' '
'
' '
'
'
'
'
'
'
'
'
' ' ' '
1
0.2
1
t
-100
-
50
0
50
100
Months
before/cfter eruption
0.41
" "
I'
"
'
" "
'
"
'
'
1
t
V
-0.4L,,
.
I
I I I I
I,
1.1
I
I,,
I
-100
-50
0
50
100
Months
before/after eruption
Figure
4.
(a) Composite sequence
of
low-pass filtered monthly global land-surface air with sea-surface temperatures around the time
of
five
tropical volcanic eruptions
(Krakatau,
Pebe-Soufiere-Santa Maria (composite), Agung, El Chichh, Pinatubo) (solid line). Values are
expressed
as
anomalies relative to the
5-year
pre-eruption periods. The dashed lines
are
f
1
standard
mr.
(b)
As (a) with the influence of the El
NifiWSouthem Oscillation removed (see text). (c) As
(b)
but showing individual sequences
for
Pinatubo (light solid line) and
for
the other
eruptions (dashed lines), along with the composite sequence (heavy solid line)
MOUNT PINATUBO IMPACT ON TEMPERATURES
495
-1.0
3
8
-
-
-
- -
-
-
I
I
I
I
I I
I
I
I
I
I I
I I
I I
Monthly MSU 4 global temperature anomalies for lower stratosphere,
relative to a
1984-90
average.
[
Data
to December
1995
]
1.57
I
I
I
I
1
I
I
I
I
I
I
I
-0.5
1
Figure
5.
Monthly MSU-4
global temperature anomalies
for
the
lower
stratosphere, relative to a
1984-1990
average
(Angel], 1993) and the eruption of Nyamuragira in Ahca in December 198
1
(Dutton and Christy, 1992) may have
contributed to the warming before El Chichon. The solar-cycle modulation of ozone and human-induced ozone
depletion may also have contributed, respectively, to the fluctuations and downward trend of temperature in Figure
5
(Folland
et
al.,
1992; McCormick
et
al.,
1995). The stratospheric warming following Pinatubo was modelled
successfdly by Graf
et
al.
(1 993). The warmings following both El Chich6n and Pinatubo were followed by stronger
coolings, in which the chemistry of ozone depletion in the presence of volcanic aerosols may be implicated
(McCormick
et
al.,
1995).
3. DISCUSSION
Our demonstration of the consistent effects of Pinatubo and other tropical eruptions on Northern Hemisphere winter
atmospheric circulation is in accord with recent observational findings (Groisman, 1992; Robock and Mao, 1992,
1995; Graf
et
al.,
1994). These papers, along with the modelling studies of Graf
et
al.
(1993) and Kirchner
and
Graf
(1995), suggest that the following processes may be in operation. The warming of the tropical stratosphere (e.g.
Labitzke and McCormick, 1992) imposes an anomalous westerly thermal wind at these levels in mid-latitudes thus
strengthening the winter polar stratospheric vortex. As a result, more planetary wave energy is thought to be trapped
in the middle and high-latitude troposphere (Graf
et
al.,
1994), giving enhanced westerlies overall,
as
in Figure 3,
and the positive surface temperature anomalies seen in Figure 2(a). The ‘ECHAM2’ model used by Graf
et
al.
(1 993) and Kirchner and Graf
(
1995) has four levels between 10 hPa and
100
hPa and three levels between 100 hPa
and
200
hPa (Roeckner
et
al.,
1992), probably enabling a better simulation of troposphere-stratosphere interactions
than with the GISS model (see section
2.1),
which has layers representing 10-70 hPa, 70-150 hPa, and 15&
200 hPa (Hansen
et
al.,
1996).
496
D.
E. PARKER
ET AL.
A
similar winter atmospheric circulation pattern in the Northern Hemisphere may, however, also occur without
volcanic triggering (Baldwin
et
al.,
1994; Graf
et
al.,
1994; Kodera and Yamazaki, 1994). There were, for example,
enhanced westerlies over northern Eurasia in the winters of 1988-1989 and 1994-1995 (not shown, but Figure l(b)
indicates warmth in 1994-1995), when there was no volcanically induced differential warming of the tropical
stratosphere.
So
although overall post-tropical-eruption surface and tropospheric cooling appears to be real, it may
be difficult to detect because of the consequential and coincidental changes
of
atmospheric circulation, which may
not be unique to post-eruption seasons. In a given location, especially at high latitudes, there may not be a volcanic
cooling signal (Kelly
et
al.,
1996). Furthermore, volcanic aerosols are not the only influence on tropical stratospheric
temperatures. For example, the impacts of the solar 1 1-year cycle
of
ultraviolet radiation, and the QBO, on both the
stratosphere and the troposphere have been modelled by Rind and Balachandran (1995) whose results showed
qualitative agreement with the observed extratropical response (e.g. Labitzke and van Loon, 1988). In a study of the
aftermath
of
the eruption of
El
Chichon, Dunkerton and Delisi (1991) diagnosed competing influences of volcanic
aerosols, the QBO, and extratropical forcing, on the tropical upper stratosphere. However, the volcanic effects
dominated temperature changes in the tropical lower stratosphere,
as
discussed also in section
2.3.
Kirchner and Graf (1995) found the observational data base on its
own
to be inadequate to clearly resolve the
separate and combined climatic impacts of volcanic eruptions and
El
Niiio events. They therefore also analysed
atmospheric model simulations for Northern Hemisphere winter with
El
Niiio and volcanic forcing, using
eigenvector techniques to isolate and assess the El Niiio and volcanic signals. The results showed some accord
with the limited observational evidence, e.g. in the volcanic case there was warming at the surface and in the lower
troposphere over northern Eurasia, despite the limitation of the simulations to perpetual January.
A
combined
empirical-modelling approach is expected to offer the best way forward in this, as in many other, areas of climatic
research.
ACKNOWLEDGEMENTS
Tracy Basnett, Andrew Colman, Robert Hackett, and Matthew O’Donnell provided valuable support in
data
analysis
and graphics production.
REFERENCES
Angell,
J.
K. 1993. ‘Comparison of stratospheric warming following Agung, El Chich6n and Pinatubo volcanic eruptions’,
Geophys. Res.
Lea,
Baldwin, M.
I?,
Cheng,
X.
and Dunkerton, T. J. 1994. ‘Observed correlations between winter-mean tropospheric and stratospheric circulation
anomalies’,
Geophys. Res. Len.,
21,
1141-1
144.
Bottomley, M., Folland, C. K., Hsiung, J., Newell, R. E. and Parker, D. E. 1990.
Global
Ocean
Surjace
Temperature Atlas (GOSTA),
Joint
Meteorological Office/Massachusetts Institute of Technology Project. Project supported by
US
Department of Energy, US National Science
Foundation and
US
Office of Naval Research. Publication funded by UK Departments of Energy and Environment. 20
+
iv pp. and 3 13
plates. HMSO, London.
20,
715-718.
Christy, J. R. and Drouilhet,
S.
J. 1994. ‘Variability in daily zonal mean lower-stratospheric temperatures’,
1
Climate,
7,
106120.
Christy,
J.
R. and McNider, R. T. 1994. ‘Satellite greenhouse signal’,
Nature,
367,
325.
Dunkerton, T.
J.
and Delisi, D.
I?
1991. ‘Anomalous temperature and zonal wind in the tropical upper stratosphere, 1982/1983’,
1
Geophys.
Res.,
96,
2263 1-22641.
Dutton,
E.
G.
and Christy,
J.
R. 1992. ‘Solar radiative forcing at selected locations and evidence for global lower tropospheric cooling following
the eruptions of El ChichQ and Pinatubo’,
Geophys. Res. Lett.,
19,
2313-2316.
Folland, C.
K.,
Karl,
T. R. and Vinnikov, K. Ya. 1990. ‘Observed climate variations and change’, in Houghton,
J.
T.,
Jenkins,
G.
J.
and
Ephraums, J. J. (eds),
Climate Change, the IPCC scienh>c Assessment,
Section 7, WMO/UNEP, IPCC, Cambridge University Press,
Cambridge, pp. 195-238.
Folland, C. K.,
Karl,
T. R., Nicholls, N., Nyenzi, B.
S.,
Parker,
D.
E. and Vinnikov, K. Ya. 1992. ‘Observed climate variability and change’, in
Houghton, J. T., Callander, B. A. and Vamey,
S.
K. (eds),
Climate Change
1992--The
Supplementary Reporr
to
the IPCC scienh&
Assessment,
Section C, WMO/UNEP, IPCC, Cambridge University
Press,
Cambridge, pp. 135-170.
Glantz, M.
H.,
Katz,
R. W.
and
Nicholls,
N.
(eds)
1991.
Teleconnections Linking Worldwide Climate Anomalies,
Cambridge University
Press,
Cambridge,
x
+
535
pp.
Graf, H.-F.,
Kirchner,
I.,
Robock, A. and Schult,
1.
1993. ‘Pinatubo eruption winter climate effects: model versus observations’,
Climate
m.,
9,
Graf,
H.-F., Perlwitz,
J.
and Kirchner,
I.
1994. ‘Northern Hemisphere tropospheric mid-latitude circulation after violent volcanic eruptions’,
Beitr Phys. Amos.,
67,
3-13.
Grant, W.
B.,
Browell, E.
V,
Fishman,
J.,
Brackett,
V
G.,
Veiga, R. E., Nganga, D., Minga, A., Cros, B., Butler, C. F., Fenn, M. A,, Long, C.
S.
and Stowe,
L.
S.
1994. ‘Aerosol-associated changes in tropical Stratospheric
ozone
following the eruption of Mount Pinatubo’,
1
Geophys.
Res.,
99,
8197-8211.
81-93.
MOUNT PINATUBO IMPACT ON TEMPERATURES
497
Groisman,
F‘.
Ya.
1992.
‘Possible regional climate consequences of the Pinatubo eruption: an empirical approach’, Geophys. Res. Lett.,
19,
1603-
Halpert, M.
S.,
Ropelewski, C. F., Karl, T. R., Angell, J. K., Stowe, L. L., Heim, R. R., Jr., Miller, A. J. and Rodenhuis, D. R.
1993. ‘1992
brings
Hansen, J., Fung,
I.,
Lacis,
A.,
Rind, D., Lebedeff,
S.,
Ruedy, R., Russell,
G.
and Stone,
I?
1988.
‘Global climate changes as forecast by Goddard
Hansen,
J.,
Lacis, A., Ruedy,
R.
and Sato, M.
1992.
‘Potential climate impact of Mount Pinatubo eruption’, Geophys. Res. Lett.,
19,
215-218.
Hansen, J., Sato, M., Ruedy, R., Lacis,
A.,
Asamoah,
K.,
Borenstein,
S.,
Brown, E., Cairns, B., Caliri,
G.,
Campbell, M., Cum, B., decastro,
S.,
Druyan, L., Fox, M., Johnson, C., Lemer, J., McCormick, M.
I?,
Miller, R., Minnis, P., Morrison, A,, Pandolfo,
L.,
Rambem,
I.,
Zaucker,
F., Robinson, M., Russell,
F‘.,
Shah,
K.,
Stone,
I?,
Tegen,
I.,
Thomason,
L.,
Wilder, J. and Wilson, H.
1996.
‘A Pinatubo climate modelling
investigation’, in Fiocco,
G.,
Fua, D. and Visconti,
G.
(eds), The EApects ofMt Pinatubo Eruption on the Aimosphere and Climate, NATO AS1
Series Volume, Subseries
I,
Global Environment Change, Springer-Verlag,
233-272.
1606.
return
to moderate global temperatures’, Eos (Am. Geophys. Union),
74,
433439.
Institute for Space Studies three-dimensional model’,
1
Geophys. Res.,
93,
9341-9364.
Hitchman, M. H., McKay, M. and Trepte, C. R.
1994.
‘A climatology of stratospheric aerosol’,
1
Geophys. Res.,
99,
20689-20700.
Jones, P. D.
1988.
‘The influence of ENS0 on global temperatures’, Climate Monitor,
17,
80-89.
Jones, P. D.
1994.
‘Hemispheric surface air temperature variations: a reanalysis and an update to
1993’,
1
Climate,
7,
1794-1802.
Kelly,
P.
M., Jia,
F‘.
and Jones,
I?
D.
1996.
‘The spatial temperature response to large explosive volcanic eruptions’, Int.
1
Climatol., in press.
Kirchner,
1.
and Graf, H.-F.
1995.
‘Volcanoes and El Niiiesignal separation in winter’, Climate Dyn.,
11,
341-358.
Kodera, K. and Yamazaki,
K.
1994.
‘A possible influence of recent polar stratospheric coolings on the troposphere in the Northem Hemisphere
Kolomeev, M.
P.,
Nikonov,
S.
A,, Sorokovikova,
0.
S.
and Khmelevtsov,
S.
S.
1993.
‘Simulation of the Northern Hemisphere climate response to
Labitzke, K.
1994.
‘Stratospheric temperature changes after the Pinatubo eruption’,
1
Amos. Ter,: Phys.,
56,
1027-1034.
Labitzke, K. and McCormick, M. P.
1992.
‘Stratospheric temperature increases due to Pinatubo aerosols’, Geophys. Res. Lett.,
19,
207-210.
Labitzke, K. and van Loon, H.
1988.
‘Associations between the
1
I-year solar cycle, the QBO and the atmosphere. Part
I:
the troposphere and
Madden, R. A., Shea, D. J., Branstator,
G.
W., Tribbia, J. J. and Weber, R.
0.
1993.
‘The effects of imperfect spatial and temporal sampling on
Mass, C. F. and Portman, D. A.
1989.
‘Major volcanic eruptions and climate: a critical evaluation’,
1
Climate,
2,
566593.
McCormick, M.
P.,
Thomason, L. W. and Trepte, C. R.
1995.
‘Atmospheric effects of the Mt Pinatubo eruption’, Nature,
373,
399404.
Pan,
Y.
H. and Oort, A. H.
1983.
‘Global climate variations connected with sea surface temperature anomalies in the eastem equatorial Pacific
Parker, D. E. and Brownscombe, J.
L.
1983.
‘Stratospheric warming following the
El
Chichon volcanic eruption’, Nature,
301,
406-408.
Parker, D. E. and Cox, D.
1.
1995.
‘Towards a consistent global climatological rawinsonde data-base’, Int.
1
Climatol.,
15,
473496.
Parker, D. E. and Jones,
F‘.
D.
1991.
‘Global warmth in
1990’,
Weather,
46,
302-31
1.
Parker, D. E., Jones,
P.
D., Folland, C.
K.
and Bevan,
A.
1994.
‘Interdecadal changes of surface temperature since the late nineteenth century’,
1
Rind,
D.
and Balachandtan,
N.
K.
1995.
‘Modelling the effects of UV variability and the QBO on the troposphere-stratosphere system. Part
11:
Robock, A.
1991.
‘The volcanic contribution to climate change of the past
100
years’, in Schlesinger, M. E. (ed.), Greenhouse-gas-induced
Robock, A. and Liu,
Y.
1994.
‘The volcanic signal in Goddard Institute for Space Studies three-dimensional model simulations’,
1
Climate,
7,
Robock, A. and Mao,
J.
1992.
‘Winter warming from large volcanic eruptions’, Geophys. Res. Let?.,
19,
2405-2408.
Robock, A. and Mao, J.
1995.
‘The volcanic signal in surface temperature observations’,
1
Climate,
8,
10861
103.
Roeckner, E., Arpe, K., Bengtsson, L., Brinkop,
S.,
Diimenil, L., Esch, M., Kirk,
E.,
Lunkeit, F., Ponater, M., Rockel, B., Sausen, R., Schlese,
U.,
Schubert,
S.
and Windelband, M.
1992.
‘Simulation of the present-day climate with the ECHAM model: impact of model physics and
resolution’, Max-Planck-Institut
fiir
Meteorologie Report No.
93,
Hamburg,
172
pp.
Ropelewski, C.
F.
and Jones, P. D.
1987.
‘An
extension of the Tahiti-Darwin Southern Oscillation Index’, Mon. Wea. Rev.,
115,
2161-2165.
Sato, M., Hansen, J. E., McCormick, M. P. and Pollack, J. B.
1993.
‘Stratospheric aerosol optical depths,
185&1990’,
1
Geophys. Res.,
98,
Shine, K. P., Derwent, R.
G.,
Wuebbles, D. J. and Morcrette, J.-J.
1990.
‘Radiative forcing of climate’, in Houghton, J. T., Jenkins,
G.
J. and
Ephraums, J.
J.
(eds), Climate Change, the
IPCC
Scientific Assessment, Section
2,
WMO/UNEP,
IPCC, Cambridge University Press,
Cambridge, pp.
41-68.
Spencer, R. W. and Christy, J. R.
1992.
‘Precision and radiosonde validation of satellite gridpoint temperature anomalies. Part
11:
a tropospheric
retrieval and trends during
1979-90’,
1
Climate,
5,
858-866.
Spencer, R. W. and Christy, J. R.
1993.
‘Precision lower stratospheric temperature monitoring with the MSU: technique, validation and results
1979-1991’,
1
Climate,
6,
1194-1204.
Spencer, R. W., Christy, J.
R.
and Grody, N. C.
1990.
‘Global atmospheric temperature monitoring with satellite microwave measurements:
method and results
1979-84’,
1
Climate,
3,
11
11-1
128.
Trepte, C. R., Veiga, R. E. and McCormick, M.
P.
1993.
‘The
poleward dispersal of Mount Pinatubo volcanic aerosol’,
1
Geophys.
Res.,
98,
winter’, Geophys. Res. Lett.,
21,
809-812.
the eruption of Mount Pinatubo’, Russian Meteorol. Hydrol.,
4,
9-13.
stratosphere in the Northern Hemisphere in winter’,
1
Atmos. Terr Phys.,
50,
197-206.
estimates of the global mean temperature: experiments with model data’,
1
Climate,
6,
1057-1066.
Ocean for the
1958-73
period’,
Mon.
Wea. Rev,,
111,
12441258.
Geophys. Res.,
99,
14373-14399.
The troposphere’,
1
Climate,
8,
2080-2095.
Climatic Change: a Critical Appmisal
of
Simulations and Observations, Elsevier, Amsterdam, pp.
429-443.
4455.
22987-22994.
18563-18573.
... Although the impacts from large volcanic eruptions on the global environment have been widely studied (e.g., Hofmann, 1987;Grattan and Pyatt, 1999;Parker et al., 1996;Oppenheimer, 2002;Self, 1845), those of lower tropospheric emissions from persistently degassing volcanoes still remain poorly known. On a time-averaged basis, gas emissions from persistent passive volcanic degassing greatly exceed those from sporadic eruptive activity (e.g., Andres and Kasgnoc, 1998;Oppenheimer et al., 2003), producing significant long-term (years to decades) effects at local and regional scales, both on humans and the environment (e.g., Tortini et al., 2017 and references therein). ...
Article
Full-text available
Volcanic gas dispersal can be a serious threat to people living near active volcanoes since it can have short- and long-term effects on human health, and severely damage crops and agricultural land. In recent decades, reliable computational models have significantly advanced, and now they may represent a valuable tool to make quantitative and testable predictions, supporting gas dispersal forecasting and hazard assessments for public safety. Before applying a specific modelling tool into hazard quantification, its calibration and its sensitivity to initial and boundary conditions should be carefully tested against available data, in order to produce unbiased hazard quantifications. In this study, we provided a number of prototypical tests aimed to validate the modelling of gas dispersal from a hazard perspective. The tests were carried out at La Soufrière de Guadeloupe volcano, one of the most active gas emitters in the Lesser Antilles. La Soufrière de Guadeloupe has shown quasi-permanent degassing of a low-temperature hydrothermal nature since its last magmatic eruption in 1530 CE, when the current dome was emplaced. We focused on the distribution of CO2 and H2S discharged from the three main present-day fumarolic sources at the summit, using the measurements of continuous gas concentrations collected in the period March–April 2017. We developed a new probabilistic implementation of the Eulerian code DISGAS-2.0 for passive gas dispersion coupled with the mass-consistent Diagnostic Wind Model, using local wind measurements and atmospheric stability information from a local meteorological station and ERA5 reanalysis data. We found that model outputs were not significantly affected by the type of wind data but rather upon the relative positions of fumaroles and measurement stations. Our results reproduced the statistical variability in daily averages of observed data over the investigated period within acceptable ranges, indicating the potential usefulness of DISGAS-2.0 as a tool for reproducing the observed fumarolic degassing and for quantifying gas hazard at La Soufrière. The adopted testing procedure allows for an aware application of simulation tools for quantifying the hazard, and thus we think that this kind of testing should actually be the first logical step to be taken when applying a simulator to assess (gas) hazard in any other volcanic contexts.
... Dynamical changes and subsidence associated with El Niño might have caused higher cooling in the monsoon season of 2012 than in 2011. This cooling is a factor of 10 smaller than the cooling caused by the Mt Pinatubo eruption, which amounts to −0.6 °C to −0.5 °C global mean surface temperature change during 1992-1993 51 . Observations suggest that large volcanic eruptions for the last 150 years have produced a global mean surface cooling of 0.3°C 52 . ...
Article
Full-text available
The Indian summer monsoon rainfall (ISMR) is vital for the livelihood of millions of people in the Indian region; droughts caused by monsoon failures often resulted in famines. Large volcanic eruptions have been linked with reductions in ISMR, but the responsible mechanisms remain unclear. Here, using 145-year (1871–2016) records of volcanic eruptions and ISMR, we show that ISMR deficits prevail for two years after moderate and large (VEI > 3) tropical volcanic eruptions; this is not the case for extra-tropical eruptions. Moreover, tropical volcanic eruptions strengthen El Niño and weaken La Niña conditions, further enhancing Indian droughts. Using climate-model simulations of the 2011 Nabro volcanic eruption, we show that eruption induced an El Niño like warming in the central Pacific for two consecutive years due to Kelvin wave dissipation triggered by the eruption. This El Niño like warming in the central Pacific led to a precipitation reduction in the Indian region. In addition, solar dimming caused by the volcanic plume in 2011 reduced Indian rainfall.
... By adopting the method of Gao and Gao (2017), each of the selected eruptions is investigated by plotting the 60 months (i.e. 5 years) prior to and 60 months (i.e. 5 years) following each eruption. Temperature anomalies are calculated as the difference of each month's mean from the five-year pre-eruption mean (Parker et al. 1996;Dätwyler et al. 2018). Since the record only begins in 1834, Cosiguina could only be investigated for 12 months before and 60 months after the eruption, so anomalies are calculated as a departure from the same five-year pre-eruption mean as used for Amargura (i.e. ...
Article
Full-text available
Improving scientific knowledge of volcanic eruptions and their impact on climate is important for testing and improving climate projection models. Despite substantive work on the impacts of major volcanic eruptions on global to regional scale climate, most studies have focussed on the northern hemisphere, with little information available for the southern hemisphere. Nevertheless, there is emerging evidence suggesting that major volcanic eruptions significantly influence weather patterns and climates of the southern hemisphere. Here we examine the climatic impact of major nineteenth century volcanic eruptions at various temporal scales for southernmost Africa (i.e. Cape Town). The oldest and longest available daily instrumental weather record for southern Africa (the South African Astronomical Observatory record) is used to test possible temperature responses following seven major volcanic eruptions (Cosiguina, 1835; Amargura, 1846; Cotopaxi, 1855; Makian, 1861; Cotopaxi, 1877; Krakatau, 1883; Tarawera, 1886) during the period 1834–1899. Following all the eruptions (for which data are available), a mean negative temperature departure is recorded in Cape Town in the second year post-eruption. The most immediate (first ten months) negative temperature response is noted following the four strongest eruptions. Tarawera, the only SH eruption, recorded the strongest and most immediate (months 1–10) mean negative temperature departure (− 0.54 °C). The importance of investigating post-eruption climatic responses at a seasonal temporal scale is demonstrated; for instance by the identification of cooler than ‘normal’ but extreme unidirectional temperature departures during austral autumn. Similarly, investigations at the monthly temporal scale enabled the identification of an increase in extreme opposing month-to-month temperature variability following such eruptions.
... Lors d'éruptions importantes, ces cendre volcaniques et ces aérosols soufrés peuvent se déplacer sur plusieurs milliers de kilomètres et atteindre la stratosphère, engendrant ainsi un refroidissement de l'atmosphère sur des périodes de temps assez longues pouvant aller jusqu'à plusieurs années. Ce fut le cas avec l'éruption du Tambora situé en Indonésie et ayant eu lieu en 1815, ou encore avec celle du Pinatubo situé dans l'archipel des Philippines et ayant eu lieu en 1991, engendrant un refroidissement global de l'ordre de 0.5°C au cours de l'année suivante (Parker et al., 1996). À l'inverse des volcans cités précédemment et qui sont de type explosif (émission de laves fragmentées dans l'atmosphère), les volcans de type effusif (coulées de laves fluides à la surface du volcan) tel que l'Etna, sont une source continue de gaz soufré (Allard et al., 1991;Oppenheimer et al., 2003). ...
Thesis
La région Euro-méditerranéenne est soumise à de fortes charges en aérosols d’origine variée et présentant une forte variabilité spatio-temporelle. Le climat de cette région va en être impacté suite à leur effet direct sur le rayonnement mais aussi à travers leurs effets semi-direct et indirects sur les nuages et la dynamique atmosphérique. Ces travaux de thèse, s’inscrivant dans les programmes de recherche Med-CORDEX et ChArMEx, vont aborder au travers de la modélisation climatique régionale la question de l’impact radiatif direct des différents aérosols sur la période historique, leur évolution entre la période 1971-2000 et la période 2021-2050 ainsi que celle de la sensibilité du climat futur de cette région à ces aérosols. Afin d’avoir une prise en compte la plus complète possible des aérosols anthropiques dans le modèle climatique régional ALADIN-Climat, utilisé tout au long de ce travail de thèse, un nouveau module d’aérosols simplifié permettant de représenter les particules de nitrate et d’ammonium a été implémenté dans son schéma interactif d’aérosols TACTIC. Un ensemble de simulations, prenant en compte ou non les particules de nitrate et d’ammonium, a été réalisé sur la période 1979-2016. Les résultats ont montré l’impact important de ces particules atmosphériques sur le climat de la région Euro-Méditerranéenne avec une contribution à hauteur de 40% à l’AOD totale (à 550 nm) ainsi qu’un forçage radiatif direct supérieur à celui des particules de sulfate et de carbone organique à partir de l’année 2005. Sur une période de temps plus longue et en utilisant différents scénarios, les résultats montrent une baisse de 35% de l’AOD totale sur l’Europe entre les périodes 1971-2000 et 2021-2050. Celle-ci est principalement due à la forte diminution de l’AOD des aérosols de sulfate compensée en partie par la hausse des nitrates. Ces derniers auront par ailleurs la contribution à l’AOD totale la plus élevée sur l’Europe, à hauteur de 45%, sur la période future. Cette évolution des différents aérosols va impacter leur forçage radiatif direct avec notamment une baisse significative de celui exercé par les particules de sulfate et une hausse de celui des aérosols de nitrate et d’ammonium. Ces changements, robustes en fonction des différents scénarios, expliquent en moyenne annuelle environ 6% du réchauffement climatique attendu sur l’Europe entre les deux périodes, principalement dû aux interactions aérosols-rayonnement mais également par une modification de l’albédo des nuages (premier effet indirect) et de la dynamique atmosphérique sur cette région.
... Some synchronization between the simulations and observations can be found in the historical part of the CMIP5 projections ( Supplementary Fig. 1). This synchronization can be attributed to the forcing by the observed atmospheric composition (which mostly varies by the greenhouse gas emissions and large volcanic eruptions; e.g., 1992-1993 cooling related to the Mount Pinatubo eruption 51,52 , the effects of the Agung eruption in 1963, and the El Chichon eruption in 1982). The climate system responded to the volcanic eruptions within several years. ...
Article
Full-text available
Climate predictions are only meaningful if the associated uncertainty is reliably estimated. A standard practice is to use an ensemble of climate model projections. The main drawbacks of this approach are the fact that there is no guarantee that the ensemble projections adequately sample the possible future climate conditions. Here, we suggest using simulations and measurements of past conditions in order to study both the performance of the ensemble members and the relation between the ensemble spread and the uncertainties associated with their predictions. Using an ensemble of CMIP5 long-term climate projections that was weighted according to a sequential learning algorithm and whose spread was linked to the range of past measurements, we find considerably reduced uncertainty ranges for the projected global mean surface temperature. The results suggest that by employing advanced ensemble methods and using past information, it is possible to provide more reliable and accurate climate projections. The ensemble spread of climate models is often interpreted as the uncertainty of the projection, but this is not always justified. Applying learning algorithms to an ensemble of climate predictions allows for a significant uncertainty reduction of projected global mean surface temperatures compared to the ensemble spread.
Article
Full-text available
About 74,000 years ago Earth’s climate abruptly transitioned to particularly severe cold and dry conditions, which lasted for several millennia. An incomplete eruption record may be why volcanic eruptions were dismissed as the trigger.
Preprint
Full-text available
The Mt. Pinatubo eruption in 1991 had a severe impact on the Earth system with a well-documented warming of the tropical lower stratosphere and a general cooling of the surface. This study focuses on the impact of this event on the mesosphere by analyzing solar occultation temperature data from the Halogen Occultation Experiment (HALOE) instrument on the Upper Atmosphere Research Satellite (UARS). Previous analysis of lidar temperature data found positive temperature anomalies of up to 12.9 K in the upper mesosphere that peaked in 1993 and were attributed to the Pinatubo eruption. Fitting the HALOE data according to a previously published method indicates a maximum warming of the mesosphere region of 3.3 K and does not confirm significantly higher values reported for that lidar time series. An alternative fit is proposed that assumes a more rapid response of the mesosphere to the volcanic event and approximates the signature of the Pinatubo with an exponential decay function having an e-folding time of 6 months. It suggests a maximum warming of 5.5 K if the mesospheric perturbation is assumed to reach its peak 4 month after the eruption. We conclude that the HALOE time series probably captures the decay of a Pinatubo-induced mesospheric warming at the beginning of its measurement period.
Thesis
Anthropogenic atmospheric aerosols have been recognized to have significantly affected the climate system through their interactions with radiation and cloud during the last decades. Besides these well-known butpoorly-understood physical processes in the atmosphere, recent studies reported strong influences of aerosols on the carbon cycle, especially its terrestrial component. The changes in carbon cycle will further alter the climate through the climate-carbon feedback. It remains uncertain how much anthropogenic aerosols perturb the land carbon cycle. This thesis aims to quantify and attribute the impacts of anthropogenic aerosols on the terrestrial cycle using a modeling approach. In Chapter 2, a set of offline simulations using the ORCHIDEE land surface model driven by climate fields from different CMIP5 generation climate models were performed to investigate the impacts of anthropogenic aerosols on the land C cycle through their impacts on climate. The results indicate an increased cumulative land C sink of 11.6-41.8 PgC during 1850-2005 due to anthropogenic aerosols. The increase in net biome production (NBP) is mainly found in the tropics and northern mid latitudes. Aerosol-induced cooling is the main factor driving this NBP changes. At high latitudes, aerosol-induced cooling caused a stronger decrease in gross primary production (GPP) than in total ecosystem respiration (TER), leading to lower NBP. At mid latitudes, cooling‐induced decrease in TER is stronger than for GPP, resulting in a net NBP increase. At low latitudes, NBP was also enhanced due to the cooling‐induced GPP increase, but regional precipitation decline in response to anthropogenic aerosol emissions may negate the effect of temperature. As climate models currently disagree on how aerosol emissions affect tropical precipitation, the precipitation change in response to aerosols becomes the main source of uncertainty in aerosol-caused C flux changes. The results suggest that better understanding and simulation of how anthropogenic aerosols affect precipitation in climate models is required for a more accurate attribution of aerosol effects on the terrestrial carbon cycle.
Article
Evidence from a newly discovered well at Berenike, a Hellenistic port on Egypt's Red Sea coast, suggests that the late third-century BC hiatus in occupation may have resulted from a multi-year drought that caused the city's freshwater source to run dry. This climatic shift was probably triggered by a volcanic eruption in 209 BC, an event that also caused a failure of the Nile to flood, leading to the famine-induced revolt of 207–186 BC in Upper Egypt. The Berenike excavations have not only uncovered the first Hellenistic city on the East African coast, but have also contributed to a better understanding of the effect of natural disasters on ancient societies.
Article
Full-text available
The global response of air temperature at 2 m above the surface to the eruptions of Mount Agung in March 1963, El Chichón in April 1982, and Mount Pinatubo in June 1991 is investigated using 11 global atmospheric reanalysis data sets (JRA-55, JRA-25, MERRA-2, MERRA, ERA-Interim, ERA-40, CFSR, NCEP-NCAR R-1, 20CR version 2c, ERA-20C, and CERA-20C). Multiple linear regression (MLR) is applied to the monthly mean time series of temperature for two periods – 1980–2010 (for 10 reanalyses) and 1958–2001 (for 6 reanalyses) – by considering explanatory factors of seasonal harmonics, linear trends, quasi-biennial oscillation (QBO), solar cycle, tropical sea surface temperature (SST) variations in the Pacific, Indian, and Atlantic Oceans, and Arctic SST variations. Empirical orthogonal function (EOF) analysis is applied to these climatic indices to obtain a set of orthogonal indices to be used for the MLR. The residuals of the MLR are used to define the volcanic signals for the three eruptions separately. First, area-averaged time series of the residuals are investigated and compared with the results from previous studies. Then, the geographical distribution of the response during the peak cooling period after each eruption is investigated. In general, different reanalyses show similar geographical patterns of the response, but with the largest differences in the polar regions. The Pinatubo response shows the largest average cooling in the 60∘ N–60∘ S region among the three eruptions, with a peak cooling of 0.10–0.15 K. The El Chichón response shows slightly larger cooling in the NH than in the Southern Hemisphere (SH), while the Agung response shows larger cooling in the SH. These hemispheric differences are consistent with the distribution of stratospheric aerosol optical depth after these eruptions; however, the peak cooling after these two eruptions is comparable in magnitude to unexplained cooling events in other periods without volcanic influence. Other methods in which the MLR model is used with different sets of indices are also tested, and it is found that careful treatment of tropical SST variability is necessary to evaluate the surface response to volcanic eruptions in observations and reanalyses.
Conference Paper
Full-text available
Global cooling of the Earth's surface has been observed following the largest volcanic eruptions of the past century, although the average cooling is perhaps less than expected from simple energy balance considerations. The Mount Pinatubo eruption, with both the climate forcing and response observed better than previous volcanoes, allows a more quantitative analysis of the sensitivity of climate to a transient forcing. We describe the strategy and preliminary results of a comprehensive investigation of the Pinatubo case.
Article
Full-text available
We present global fields of decadal annual surface temperature anomalies, referred to the period 1951-1980, for each decade from 1881-1890 to 1981-1990 and for 1984-1993. In addition, we show decadal calendar-seasonal anomaly fields for the warm decades 1936-1945 and 1981-1990. The fields are based on sea surface temperature (SST) and land surface air temperature data. The SSTs are corrected for the pre-World War II use of uninsulated sea temperature buckets and incorporate adjusted satellite-based SSTs from 1982 onward. The generally cold end of the nineteenth century and start to the twentieth century are confirmed, toegether with the substantial warming between about 1920 and 1940. Slight cooling of the northern hemisphere took place between the 1950s and the mid-1970s, although slight warming continued south of the equator. Recent warmth has been most marked over the northern continents in winter and spring, but the 1980s were warm almost everywhere. -from Authors
Article
Full-text available
It is shown that interannual variability of the northern winter stratospheric flow in 1964-1993 was closely linked to large-scale circulation anomalies in the middle troposphere. Of the known tropospheric teleconnection patterns, the one having the strongest relation to the DJF (December-February) zonal-mean stratospheric flow was the North Atlantic Oscillation (NAO). Singular value decomposition between the 500 and 50-hPa geopotential heights produced a 500-hPa structure containing elements of the NAO pattern, but including an anomaly in eastern Siberia. During this time period, the correlation of NAO-related modes to the polar lower stratosphere exceeded that of the equatorial quasi-biennial oscillation.
Article
A large portion of the global climate change of the past 100 years may be due to the effects of volcanoes, but a definitive answer is not yet clear. While effects over several years have been demonstrated with both data studies and numerical models, long-term effects, while found in climate model calculations, await confirmation with more realistic models. In this paper chronologies of past volcanic eruptions and the evidence from data analyses and climate model calculations are reviewed. -from Author
Article
During the first part of the year, the 1991-1992 ENSO episode contributed to above normal temperatures in the Northern hemisphere, while cooling during the latter part of the year was associated with the aerosol cloud produced by the June 1991 eruption of Mt. Pinatubo. By the spring of 1992, the stratospheric aerosol cloud had extended from the tropics well into both hemispheres. In this report, global surface temperature anomalies are defined as departures from the 1961-1990 base period means. As the aerosol cloud spread throughout the Northern Hemisphere during a time of increasing solar radiation, the surface temperature anomalies responded by becoming less positive over much of the the hemisphere. The presence of volcanic aerosols in the stratosphere also contributed to reduced ozone concentrations over the polar region of the Southern Hemisphere. -from Authors
Article
As a result of the eruption of Mt. Pinatubo (June 1991), direct solar radiation was observed to decrease by as much as 25–30% at four remote locations widely distributed in latitude. The average total aerosol optical depth for the first 10 months after the Pinatubo eruption at those sites is 1.7 times greater than that observed following the 1982 eruption of El Chichón. Monthly-mean clear-sky total solar irradiance at Mauna Loa, Hawaii, decreased by as much as 5% and averaged 2.4% and 2.7% in the first 10 months after the El Chichón and Pinatubo eruptions, respectively. By September 1992 the global and northern hemispheric lower tropospheric temperatures had decreased 0.5°C and 0.7°C, respectively compared to pre-Pinatubo levels. The temperature record examined consists of globally uniform observations from satellite microwave sounding units.
Article
Natural events, such as the Mt. Pinatubo eruption in the Philippines and the El Niño/Southern Oscillation (ENSO) episode in the tropical Pacific Ocean, had major impacts on the global climate in 1992. These phenomena were associated with a return to more moderate global temperatures during 1992 after several years of record or near-record high temperatures. During the first part of the year, the 1991-1992 ENSO episode contributed to above normal temperatures in the Northern Hemisphere, while cooling during the latter part of the year was associated with the aerosol cloud produced by the June 1991 eruption of Mt. Pinatubo. By the spring of 1992, the stratospheric aerosol cloud had extended from the tropics well into both hemispheres. In this report, global surface temperature anomalies are defined as departures from the 1961-1990 base period means. As the aerosol cloud spread throughout the Northern Hemisphere during a time of increasing solar radiation, the surface temperature anomalies responded by becoming less positive over much of the hemisphere. This relative cooling helped to make 1992 the coolest year since 1986. Temperatures also were dramatically cooler throughout the troposphere.