An eruption in Indonesia may have caused the bad weather that brought Napoleon down, says S.Ananthanarayanan.

The history of the battle of Waterloo, where Britain’s Lord Willington and his Prussian ally defeated Napoleon is well recorded. Apart from some errors in generalship on the part of the French, it is believed that it is the bad weather during the days of the battle that turned its course against them

Dr Matthew J Genge from Imperial College and the Natural History Museum, London writes in ‘GEOLOGY’, the journal of the Geological Society of America, that the unseasonal rain that affected the timing of the French attack may have been caused by the volcanic eruption of Mount Tambora, in Indonesia, just two months earlier. As records of 1815 are sparse, Dr Genge examined the records of another eruption in Indonesia in 1883 and concludes that it may be reasonable to believe that Mount Tambora had contributed to Napoleon’s downfall

Dr Matthew J Genge from Imperial College and the Natural History Museum, London writes in ‘GEOLOGY’, the journal of the Geological Society of America, that the unseasonal rain that affected the timing of the French attack may have been caused by the volcanic eruption of Mount Tambora, in Indonesia, just two months earlier. As records of 1815 are sparse, Dr Genge examined the records of another eruption in Indonesia in 1883 and concludes that it may be reasonable to believe that Mount Tambora had contributed to Napoleon’s downfall

Waterloo is in modern day Belgium, then part of the Dutch Kingdom. Anglo-Dutch forces, under Wellington, were stationed on the western border of Belgium and Prussian (German) forces, under Blücher, were in eastern Belgium. Napoleon decided to engage these two forces before they could get together, with others, to invade France. On the 15th of June, Napoleon was able to beat the Prussians back and he sent a force under Marshal Ney to deal with the Anglo-Dutch. But there appears to have been indecision on the part of the French commander, and delay in the deployment, which gave the Prussians time to rally to the aid of the Anglo-Dutch.

The battle of Waterloo took place on 18th June 1815. It was a horrific battle and 47,000 men died. And, although Wellington was victorious, he described it as, “the nearest-run thing you ever saw in your life”. Many commentators believe that unseasonal rain during the 16th and the 17th of June induced the French to delay the engagement till the ground dried. Dry ground was may not have been equally helpful to the enemy, as the French were clearly superior, but the lapse of time allowed the enemy to regroup. A commentator of Victor Hugo, in Les Misérables, observes,” Had it not rained on the night of 17th June, the future of Europe would have been different …an unseasonably clouded sky sufficed to bring about the collapse of a World.”

Dennis Wheeler and Gaston Demarée of the University of Sunderland (UK) and Koninklijk Meteorologisch Institut van België, Belgium had studied scattered records which had mentioned the weather. On the strength of these, and entries in individual diaries and other records, they concluded, in a paper in the journal of the Royal Meteorological Society, in 2005, that there had been an unexpected thunderstorm on the night of the 17th June and this was a factor, at least, in Napoleon’s defeat. As regards the effect of the Indonesian eruption of April 1815, they note that it was in 1816, which was ‘a year without a summer’, that the effect was manifest

Mount Tambora is volcano that is in Sumbawa, one of the islands in Indonesia.The eruption of April 1815, was the most devastating ever recorded. The climax was on 10th April, but release of vapours and ash, and smaller eruptions continued for the next six months. The volcanic ash spread, and brought down temperatures, worldwide. The following year, 2016, as a fallout, is recorded as the second coldest year in the Northern Hemisphere since 1400. The effects were outbreak of disease, frost, rainfall, worldwide, even the Indian monsoon was affected.

To say whether the climate changes recorded in June 1815 was on account of the Mount Tambura eruption, however, there is very little data available. What we do have is systematic data at the time of the 1883 Krakatau (Indonesia) eruption, of nearly comparable intensity.

The study by Dr Matthew J Genge in the journal, GEOLOGY examines the mechanics of the rise of volcanic ash into the atmosphere following an eruption. It has so far been understood that the ash, which rises as high as 50 km, would not rise above the stratosphere and into the upper reaches of the atmosphere, because the stratosphere acts as a barrier, the study says. The stratosphere is where the falling of temperature with increase in the altitude, which we see in the lower atmosphere, is replaced by rising of temperature with altitude, in the upper atmosphere. Convection driven elevation of volcanic dust is hence not likely to go beyond the stratosphere and eruptions would have little effect on the upper atmosphere.

However, the study says, there is evidence that eruptions create high electric charges which can lead to non-thermal forces to levitate charged ash particles. “Electrostatic interaction between charged volcanic ash particles and plumes having a net charge of the same polarity will unavoidably cause levitation of particles,” the study says. And “Large explosive eruptions could, therefore, have a significant effect on the global electrical circuit,” the study says. “Global suppression of cloud formation would be likely to increase atmospheric H2O content, thus in the immediate aftermath of supervolcano eruptions, recovery of the ionosphere and resumption of normal cloud formation may result in enhanced cloud cover and precipitation,” the study says.

After the 1883, Krakatau eruption, the study says, there was a dip in the temperature and the lowest rainfall recorded was while the eruption lasted. Records of the start of the effects of aerosols, as opposed to charged volcanic ash, also show that the aerosols arrived a good time later. This would partly tally with the events of 1815, where there was an unseasonal rise in rainfall two months after the eruption, while continued, aerosol dominated effects came later.

The study says that there are no records to evaluate the effect of electrostatic levitation of ash in the 2015 event but concludes that this must be so because of the records of increased rainfall. It would h not really be valid, hence, to conclude that the increased rainfall is connected with the eruption, when we are linking suppression and recovery of cloud formation due to levitation of ash with the reports of high rainfall. There is, however, as the study says, the possibility that the events are linked.

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