Era of major volcanic eruptions nears

from natural records like sulphate found in the polar ice cores and tree rings. Worryingly, this points to a number of as yet undiscovered eruptions — one as recently as 1809. The largest sulphur fallout of the last 7,000 years was in 1259. Nobody knows which volcano was responsible.

The release notes that this evidence also shows why the repercussions of volcanoes are felt far beyond the impact zone. The large eruptions of the past few millennia produced huge clouds of sulphurous dust. These caused dramatic climatic swings.

One case, in 1783, shows what a bigger eruption in Iceland could do. That year an eruption took place at Laki that was 200 times the size of the 2010 example. It emitted 122 megatons of sulphur dioxide, wiped out a fifth of the country’s population and coincides strikingly with tens of thousands of deaths in England and France.

The reason for the scale of the catastrophe may be linked to the sulphuric cloud that spread over Europe.

Documented at the time as a mysterious “haze”, this initially interacted with an area of high pressure over the continent, causing a heat wave that killed thousands. A very severe winter then followed — the result of a temperature drop as the sulphuric particles in the atmosphere reflected solar radiation that should have been reaching the Earth back into space. First the Thames and other rivers froze. Then, as the snow melted, there was widespread flooding.

These changes in the climate resulted in dramatic crop and livestock failure and the spread of disease. The death rate in England spiked in both the summer of 1783 and the following winter; an estimated 25,000 people lost their lives overall.

Laki is far from the only example of volcanoes having disastrous consequences far away. 3,600 years ago an eruption entombed the island of Santorini in the Mediterranean and, as debris hit the ocean, caused a tsunami which contaminated farmland elsewhere. Within a few generations the Minoan civilisation that had dominated the region collapsed.

In 536, a still-unidentified volcano again caused a climate swing and an agrarian crisis. It is probably no coincidence that the first pandemic of bubonic plague happened at the same time – rats would have abandoned the dying fields and headed for man-made grain stores where they spread the bacterium.

And in 1815, global cooling caused by 30 megatons of sulphur emitted from an eruption on Sumbawa, Indonesia, led to the infamous “year without a summer” of 1816 in both Europe and the Eastern United States. In the latter, the failure of crops in places like Connecticut sparked a wave of migrations westwards. In Europe, where the Napoleonic Wars had just ended, an economic crisis occurred. Amid the riots and looting were a number of pogroms — violent reprisals against Jews. They were the first in an ongoing chain of such events that reached their final, terrible conclusion with the rise of the Nazis.

These scenarios may seem unlikely today, but, Oppenheimer argues, volcanoes could still wreak havoc if we do not prepare for larger eruptions. A Laki-type event in Iceland now would do far more than upset a few indignant tourists; its sulphur cloud could add to the air pollution in modern European cities and produce a serious public health crisis. Then there is the possibility of a super-eruption, which would cause a major humanitarian disaster.

The last one we know about happened 26,000 years ago. Oppenheimer estimates that there is roughly a 1/500 chance of one recurring in the next century — odds long enough for governments to ignore, but short enough to cause serious concern.

His study recommends that international organizations already exist that could introduce measures like spot traffic bans or distribution of dust masks in a repeat of the Laki eruption. For those who find themselves in the immediate vicinity of a volcano, however, Oppenheimer says evacuation is the only real solution — adding that governments should consider creating and maintaining plans for this in potential disaster zones.

In spite of that, however, his conclusion is oddly optimistic. “Humankind has yet to run into the buffers as the result of a volcanic eruption and may have learned to adapt and benefit from them in the long-term,” Oppenheimer said. “As the global population heads towards 10 billion, the human track record shows that we can manage the consequences of eruptions with resolve, flexibility and creativity — if we prepare properly.”