Tables

Table 1: Volcanic aerosol loading of the stratosphere in $Tg$ after Stothers (1996) for volcanoes with $VEI=6$ and corrected $VEI$ after equation 3.

Volcano	Year of eruption	Mass loading in $Tg$	Corrected $VEI$
Krakatau	1883	44	6.25
Santa Maria	1902	30	6.08
Katmai	1912	11	5.64
Agung	1963	20	5.9
El Chichón	1982	14	5.75
Pinatubo	1991	30	6.08
Average		24.8	5.95

Table 2: Volcanic aerosol loading of the stratosphere in $Tg$ after Stothers (1997) for strong volcanic eruptions since 1880 with $VEI < 6$ and corrected $VEI$ after equation 3.

Volcano	Year of eruption	Mass loading in $Tg$	Corrected $VEI$
Unidentified$^{a)}$	1890	6	5.38
Soufriere/Pele	1902	5	5.3
Ksudach	1907	4	5.2
Puyehue	1921	2	4.9
Komakatake	1929	4	5.2
Paluweh	1928	3	5.08
Quizapa	1932	3	5.08
Bezymianny	1956	not significant	4$^{b)}$
Fernandino	1968	6$^{c)}$	5.38
Fuego	1974	5$^{c)}$	5.3
Average		4.2$^{d)}$	5.2$^{d)}$

$^{a)}$ Stothers (1997) gives a range of 6 to 24 $Tg$ which depends on the latitude of eruption. Since we suppose that Bogoslof (54$^{\circ}$N) may be the unidentified volcano, we use the smallest estimate of 6 $Tg$ according to the latitude of eruption. $^{b)}$ $VEI=4$ corresponds to $M=.25 Tg$. $^{c)}$ Values are taken from a scaling of the observed $AOD$ compared to the observations of Mt. Pinatubo (1991). $^{d)}$ Bezymianny eruption not considered.

Table 3: Exchange coefficients $m_{i,k}$ for different regions in % per month.

tropics $\leftrightarrow$ tropics	91
tropics $\rightarrow$ extratropics	30
extratropics $\rightarrow$ tropics	7
extratropics $\leftrightarrow$ extratropics (winter-spring)	90
extratropics $\leftrightarrow$ extratropics (summer-fall)	45
extratropics $\leftrightarrow$ winter polar vortex	10
extratropics $\leftrightarrow$ summer polar region	45
extratropics $\leftrightarrow$ polar region in moderate season	23

Table: Vertical exchange of air between stratosphere and troposphere in $\frac{10^{8}kg}{s}$ (taken from Rosenlof and Holton, 1993).

	DJF	JJA	Annual average
N hemisphere extra-tropics	-81	-26	-53.5
Tropics	114	56	85
S hemisphere extratropics	-33	-30	-31.5

Table 5: Linear correlations of the different volcanic $AOD$ time series.

	Time	Linear correlation coefficient
Time series	interval	global	$90 ^{\circ} - 30 ^{\circ} S$	$30 ^{\circ} - 0 ^{\circ} S$	$0 ^{\circ} - 30 ^{\circ} N$	$30 ^{\circ} - 90 ^{\circ} N$
Sato / Stothers	1880 - 1933	.68	.57	.56	.64	.81
Sato / this paper	1850 - 1995	.77	.75	.71	.75	.76
Stothers / this paper	1880 -1933	.94	.94	.90	.83	.90

Table 6: Linear correlation between the different volcanic forcing time series.

	time	linear correlation coefficient
Time series	interval	global	$90 ^{\circ} - 30 ^{\circ} S$	$30 ^{\circ} - 0 ^{\circ} S$	$0 ^{\circ} - 30 ^{\circ} N$	$30 ^{\circ} - 90 ^{\circ} N$
Sato / this paper	1850 - 1995	.75	.74	.70	.75	.72
Stothers / this paper	1880 -1933	.94	.95	.90	.82	.86

Table 7: Comparison of three year average forcing ($W/m^{2}$) of a volcanic eruption occuring in January and July respectively.

Latitude belt	Januar eruption	July eruption	$\hat{t}$-value of difference
$30 ^{\circ} - 30 ^{\circ} N$	-1.11	-.94	.89
$0 ^{\circ} - 30 ^{\circ} N$	-3.29	-2.98	.54
$0 ^{\circ}- 30 ^{\circ} S$	-3.28	-3.19	.15
$30 ^{\circ} - 90 ^{\circ} S$	-.98	-.96	.12