Volcanic Clouds

The estimated average air temperature above the land surface of the Earth. The thick black line. The squiggle lines are data and the grey lines give an indication of uncertainty in the estimate. Th bold black line shows the results of a model based on carbon dioxide and the effect of named volcanoes.

The estimated average air temperature above the land surface of the Earth. The squiggly lines are data and the grey lines give an indication of uncertainty in the estimate. The bold black line shows the results of a model based on the effects of carbon dioxide and the effect of named volcanoes. Figure is from the Berkeley Earth Temperature Project

The explosion of Mount Tambora in 1815 was the largest explosion in recorded history. Its catastrophic local effects – earthquakes, tsunami, and poisonous crop-killing clouds – were witnessed by many people including Sir Stamford Raffles, then governor of Java.

Curiously, one year later, while touring through France, Raffles also witnessed deserted villages and impoverished peasantry caused by the ‘year without a summer’ that caused famine throughout Europe.

But at the time no-one connected the two events! The connection was not made until the late 20th Century when scientists were investigating the possibility of a ‘nuclear winter’ that might arise from multiple nuclear explosions.

Looking at our reconstructed record of the air temperature above the land surface of the Earth at the head of this article, we can see that Tambora lowered the average surface temperature of the Earth by more than 1 °C and its effects lasted for around three years.

Tambora erupted just 6 years after a volcanic explosion in 1809 whose location is still unknown. We now know that together they caused the decade 1810-1820 to be exceptionally cold. However, at the time the exceptional weather was just experienced as an ‘act of god’.

In Tambora: The Eruption that changed the world, Gillen D’Arcy Wood describes both the local nightmare near Tambora, and more significantly the way in which the climate impacts of Tambora affected literary, scientific, and political history around the globe.

In particular he discusses:

  • The effect of a dystopian ‘summer’ experienced by the Shelleys and Lord Byron in their Alpine retreat.
  • The emergence of cholera in the wake of a disastrous monsoon season in Bengal. Cholera went on to form a global pandemic that eventually reached the UK through trade routes.
  • The period of famine in the rice-growing region of Yunnan that led to a shift towards opium production.
  • The bizarre warming – yes, warming – in the Arctic that led to reports of ice free northern oceans, and triggered decades of futile attempts to discover the fabled North West Passage.
  • The dramatic and devastating advance of glaciers in the Swiss alps that led to advances in our understanding of ice ages.
  • The ‘other’ Irish Famine – a tale of great shame and woe – prefacing the great hunger caused by the potato-blight famines in later decades.
  • The extraordinary ‘snow in June’ summer in the eastern United States

Other Volcanic Clouds

Many Europeans will recall the chaos caused by the volcanic clouds from the 2010 eruptions of the Icelandic volcano Eyjafjallajökull (pronounced like this  or phonectically ‘[ˈeɪjaˌfjatlaˌjœːkʏtl̥]).

The 2010 eruptions were tiny in historical terms with effects which were local to Iceland and nearby air routes. This is because although a lot of dust was ejected, most of it stayed within the troposphere – the lower weather-filled part of the atmosphere. Such dust clouds are normally rained out over a period of a few days or weeks.

Near the equator the boundary between the troposphere and stratosphere – known as the tropopause – is about 16 km high, but this boundary falls to around 9 km nearer the poles.

For a volcanic cloud to to have wider effects the volcanic explosion must push it above the tropopause into the stratosphere. Tiny particles can be suspended here for years, and have a dramatic effect on global climate.

Laki

Tambora may have been ‘the big one’ but it was not alone. Looking at our reconstructed air temperature record at the head of this article, we can see that large volcanic eruptions are not rare. And the 19th Century had many more than the 20th Century.

Near the start of the recorded temperature history is the eruption of Laki in Iceland (1783-84). Local details of this explosion were recorded in the diary of Jon Steingrimsson, and in their short book Island on Fire, Alexandra Witze and Jeff Kanipe describe the progression of the eruption and its effects further afield – mainly in Europe.

In the UK and Europe the summer consisted of prolonged ‘dry fogs’ that caused plants to wither and people to fall ill. On the whole people were mystified by the origin of these clouds, even though one or two people – including the prolific Benjamin Franklin – then US Ambassador to France – did in fact make the connection with Icelandic volcanoes.

Purple Clouds

Prior to the two books on real volcanic clouds, I had previously read a fictional account of such an event: The Purple Cloud by M P Shiel, published in 1901, and set in the early decades of that century.

This is a fictional, almost stream-of-consciousness, account of how an Arctic explorer discovers a world of beauty at the North Pole – including un-frozen regions. But by violating Nature’s most hidden secrets, he somehow triggers a series of volcanic eruptions at the Equator which over the course of a couple of weeks kill everyone on Earth – save for himself.

I enjoyed this book, but don’t particularity recommend it. However what is striking to me now having since read accounts of these genuine historical events is that the concept of a globally significant volcanic cloud actually existed at the end of the nineteenth Century.

Final Words

The lingering flavour of these books – factual and fictional – is that historically there have been poorly-appreciated tele-connections between historical events.

Now, we live in a world in which the extent and importance of these global tele-connections has never been greater.

And in this world we are vulnerable to events such as volcanic clouds which – as the chart at the top of the page shows – affect the entire world and are not that rare.

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