View of the plume from the Eyjafjallajokull eruption (scienceblogs). More photos here
What should be a concern, it appears, however, is that this particular volcano, although in itself not that large, is often a precursor to the eruption of the Katla volcano, which is nearby but further north- east. While the current eruption started away from a glacier, the Katla lies under the Myrdalsjoekull glacier, and the precedents are not good.
"Eyjafjallajokull has blown three times in the past thousand years," Dr McGarvie told The Times, "in 920AD, in 1612 and between 1821 and 1823. Each time it set off Katla." The likelihood of Katla blowing could become clear "in a few weeks or a few months", he said.
The second Katla eruption has, historically, had much greater impacts since it has had the power to inject large volumes of particles and gases into the atmosphere that create a sufficiently dense cloud that sunlight is reduced, harvests are affected and famines result. For example when the nearby Laki fissures erupted in 1783 the results that were reported included:
Iceland's Laki volcano erupted in 1783, freeing gases that turned into smog. The smog floated across the Jet Stream, changing weather patterns. Many died from gas poisoning in the British Isles. Crop production fell in western Europe. Famine spread. Some even linked the eruption, which helped fuel famine, to the French Revolution. Painters in the 18th century illustrated fiery sunsets in their works.The last eruption of Katla was not that severe, although there was severe flooding. But it can be violent, throwing large volumes of material into the air. The consequence of the Laki eruption of 1783-4 (it lasted for eight months and ejected over 9 cubic miles of basaltic lava and a quarter of the population of Iceland died from starvation, the effect on winter temperatures in the US was evident.
The winter of 1784 was also one of the longest and coldest on record in North America. New England reported a record stretch of below-zero temperatures and New Jersey reported record snow accumulation. The Mississippi River also reportedly froze in New Orleans.
But it is not the fine particles that apparently cause the most climate impact, rather the large volumes of gases that also are ejected and turn into acid aerosols that contribute to the disastrous consequences. It has been projected that there were some 8 million tons of fluorine and 120 million tons of sulphur dioxide released. To put this in context, during the Mount Pinatubo eruption (which also had a short term cooling on global climate) the volcano is projected to have emitted some 20 million tons of sulfur dioxide and that this lowered the global temperature by perhaps 0.8 deg C in 1992. (The aerosols reflecting back more solar energy into space.)
Mount Pinatubo erupting (USGS photo)
The fissures themselves, from which the Laki lava flowed, stretch some 16- miles though not as a continuous crack, but rather the lava flowed from about 130 craters.
Laki craters (climate4you)
The general locations of the Katla to the earlier Laki and Eldgja eruptive flows is shown here:
Location of the Laki, Katla and Eldgja fissures, the current eruption is further south and west, on the hidden side of the Mydalsjokull glacier.
The severity of the impacts of these eruptions on the global climate and the resulting devastation on the harvests is a matter of record. We know that there are more coming, and, from past history the damage will be great.
That record suggests that there will soon be another serious eruption that, on past performance, will also eject large quantities of sulfur dioxide gases into the atmosphere and induce another period of cooling.
Since the previous evidence has shown that this cooling has not been good for the global health, perhaps it might be about time that folks started working on what can be done to stop, or collect these large volumes of gases before they become too predatory. Certainly the problem of neutralizing the gas or otherwise collecting it or storing it is significant (but then so is that for carbon dioxide). However we know where it is going to come from, and some of the mechanics of how it will migrate upwards. There are large unknowns in terms of how we might capture, control, or neutralize a lot of the acid-forming gasses, but the size of the problem has never stopped us before.
And if the problem were to be addressed by the nations of the world, perhaps we could, in time, assuage some of the known negative effects from the global cooling that we can now expect as the Icelandic eruption continues. This cooling may well already be more certain than near term global warming, and more immediately likely to occur, so under the same Precautionary Principles that are driving the huge investments in climate change already, ought we not be spending our time right now trying to find ways to stop the impact of these massive eruptions on the health of the globe.
Silly thought – but one that suggests that the problems don’t always only have one side, and that we might find out by visual observation the down-sides of too much cooling and its effect on people and agriculture, perhaps sooner than we would like.