Volcanoes and economics

Paul Sweeney: We may have harnessed nature, but the last few days flight cancellations in Europe demonstrate that nature can assert itself very strongly. What if the eruptions continue? What if other volcanoes erupt? Iceland has many volcanoes and with the right winds……

How long will the eruption last, will it impact on the food supply and on the world's climate?

The problem with volcanic eruptions is that you really don't know what they're going to do.

Sally Sennert, a Smithsonian Institution volcano expert, says that the eruption could last for months, just as Eyjafjallajokull's previous one did back in 1821-23. But she said, "there's no telling how long the eruptions could last." This volcano is Eyjafjallajokull and its eruption of ash doesn't contain much sulphur, which is needed to generate the sulphuric acid droplets that could linger in the upper atmosphere and have a cooling effect on climate.

In 1991, Mount Pinatubo in the Philippines, the second-largest eruption of the 20th century (much larger than Eyjafjallajokull), sent a sulfuric acid haze into the stratosphere, reducing global average temperatures about 0.9 degrees Fahrenheit over the following year

Back in 1783, Laki in Iceland erupted over an 8 month period during 1783-1784 from its fissure and the adjoining Grímsvötn volcano, pouring lava and also poisonous acid and sulphur clouds. These clouds killed over half of Iceland's livestock, leading to famine which in turn, killed a quarter of the population.
But it had a big impact in Europe too and some say it contributed to the French Revolution taking place. This was because it caused extremes in climate for several years with frosts in summer, droughts, clouds etc and led to food shortages all over Europe but particularly in France.

Ben Franklin wrote in 1784:

During several of the summer months of the year 1783, when the effect of the sun's rays to heat the earth in these northern regions should have been greater, there existed a constant fog over all Europe, and a great part of North America. This fog was of a permanent nature; it was dry, and the rays of the sun seemed to have little effect towards dissipating it, as they easily do a moist fog, arising from water. They were indeed rendered so faint in passing through it, that when collected in the focus of a burning glass they would scarce kindle brown paper. Of course, their summer effect in heating the Earth was exceedingly diminished. Hence the surface was early frozen. Hence the first snows remained on it unmelted, and received continual additions. Hence the air was more chilled, and the winds more severely cold. Hence perhaps the winter of 1783-4 was more severe than any that had happened for many years.

The cause of this universal fog is not yet ascertained... or whether it was the vast quantity of smoke, long continuing, to issue during the summer from Hecla in Iceland, (it was Laki) and that other volcano which arose out of the sea near that island, which smoke might be spread by various winds, over the northern part of the world, is yet uncertain.

What if this volcano continues to spew or if others erupt? We are have much better seed crops, farm systems, etc. than in 1783, but in the end, we need the sun to generate plant life.
The economic impact on the European aviation industry has already been dramatic (and on shipping in reverse), but if prolonged, it could have a bigger impact on agriculture and food prices. And this is on top of NAMA and the 20% collapse in national income (GNP) since 2007!