We never see the sun but shorn of his beams

From Apocalypse Then by Stephanie Pain.

“So long in a country not subject to fogs, we have been cover’d with one of the thickest I remember. We never see the sun but shorn of his beams, the trees are scarce discernible at a mile’s distance, he sets with the face of a red hot salamander and rises with the same complexion.” When English poet William Cowper penned these words to his friend John Newton on 29 June 1783, an unwholesome haze had been hanging over England for more than a week, inducing peculiar atmospheric effects. “Some fear to go to bed, expecting an Earthquake,” he wrote. “Some declare that he [the sun] neither rises nor sets where he did, and assert with great confidence that the day of Judgement is at hand.” By September, it looked as if their fears might be justified. On 7 September, Cowper wrote to the rector of Stock in Essex: “Such multitudes are indisposed by fevers in this country, that farmers have with difficulty gathered in their harvest, the labourers having been almost every day carried out of the field incapable of work and many die.”

In Europe they called 1783 the Year of Awe. So many strange things happened: earthquakes rocked Calabria, volcanoes erupted in Iceland and Italy, and the weather was odd too. The summer was one of the hottest ever recorded and a persistent haze cloaked most of the continent. At sunset, the skies took on spectacular colours and at night the moon was blood-red. July brought calamitous thunderstorms. And after the torrid summer came a winter so deadly cold that travellers froze to death by the roadside. If these weren’t signs of impending Armageddon, what were they?

French naturalist Mourgue de Montredon was the first to suggest a less apocalyptic explanation, at least for the weird weather and vile fog. He was sure it was no coincidence that they came so soon after a great volcanic eruption in Iceland. On 8 June, the Laki fissure – now a 25-kilometre crack in the Earth’s crust in southern Iceland – began spewing lava from dozens of vents along its length. It was one of the biggest eruptions in recorded history. In the months that followed, some 10,000 Icelanders died, a quarter of the population. But, as Montredon suspected, Laki’s malign influence stretched much further afield.

There were 10 major eruptions in the first few months. Fiery fountains of lava shot as much as 1.5 kilometres into the air, accompanied by towering pillars of ash and gas that reached as high as 13 kilometres. By the time the eruption stopped the following February, it had pumped out almost 15 cubic kilometres of lava, 122 million tonnes of sulphur dioxide, and millions more tonnes of chlorine and fluorine. In Iceland, the big killer was fluorine, which poisoned crops, livestock and people. Many of those who survived the immediate aftermath later died of fluorosis or starved in the famine that followed. But for the rest of Europe, it was the vast outpouring of sulphur dioxide that spelled trouble.

For the first six weeks of the eruption, Laki sent 1.7 million tonnes of sulphur dioxide a day into the upper reaches of the troposphere and lower stratosphere, where it was quickly converted into a sulphuric acid aerosol and swept away on the westerly jet stream towards Europe. A stable area of high pressure over the continent – usually the bringer of fine, summer weather – helped to draw the acid down towards the ground, creating a persistent fog. During July, another 33 million tonnes of the gas ended up in the jet stream.

Across Europe, people complained of the stifling heat and the dry fog that stank of sulphur, jotting down their observations in letters and diaries. Some mentioned headaches, burning eyes, tingling lips and “sickness of the throat”. Many had breathing difficulties. The grave diggers noticed something too: summer was usually their slackest time – but not this year.

The “great dry fog” arrived in England and France within a week of the eruption. Soon it stretched all the way from Scandinavia to North Africa and stayed there for most of June, July and August. This was seriously dangerous air pollution on a massive scale, says John Grattan, a geoarchaeologist at the University of Wales, Aberystwyth. And the timing could not have been worse. Combined with the hot summer weather, it was lethal. New studies of burial records from England and France suggest that Laki’s final toll may have been many tens of thousands.