Consequences in Europe
An estimated 120 mio. tons of sulfur dioxide were emitted: approximately equivalent to three times the total annual European industrial output in 2006, and also equivalent to a Mount Pinatubo-1991 eruption every three days.[6] This outpouring of sulfur dioxide during unusual weather conditions caused a thick haze to spread across western Europe, resulting in many thousands of deaths throughout 1783 and the winter of 1784.

The summer of 1783 was the hottest on record and a rare high pressure zone over Iceland caused the winds to blow to the south-east. The poisonous cloud drifted to Bergen in Norway, then spread to Prague in the Province of Bohemia by 17 June, Berlin by 18 June, Paris by 20 June, Le Havre by 22 June, and to Great Britain by 23 June. The fog was so thick that boats stayed in port, unable to navigate, and the sun was described as "blood coloured".[6]

Inhaling sulfur dioxide gas causes victims to choke as their internal soft tissue swells. The local death rate in Chartres was up by 5% during August and September, with over 40 dead. In Great Britain, the records show that the additional deaths were outdoor workers, and perhaps 2-3 times above the normal rate in Bedfordshire, Lincolnshire and the east coast. It has been estimated that 23,000 British people died from the poisoning in August and September.

The haze also heated up causing severe thunderstorms with hailstones that were reported to have killed cattle until it dissipated in the autumn. This disruption then led to a most severe winter in 1784, where Gilbert White at Selborne in Hampshire reported 28 days of continuous frost. The extreme winter is estimated to have caused 8,000 additional deaths in the UK. In the spring thaw, Germany and Central Europe then reported severe flood damage.[6]

The meteorological impact of Laki resonated on, contributing significantly to several years of extreme weather in Europe. In France a sequence of extremes included a surplus harvest in 1785 that caused poverty for rural workers, accompanied by droughts, bad winters and summers, including a violent hailstorm in 1788 that destroyed crops. This in turn contributed significantly to the build up of poverty and famine that triggered the French Revolution in 1789. Laki was only a factor in a decade of climatic disruption, as Grímsvötn was erupting from 1783–1785 and a recent study of El Niño patterns also suggests an unusually strong El-Niño effect between 1789-93.[9]
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http://en.wikipedia.org/wiki/Laki#1783_eruption