Island on Fire Page 11

  The remarkable fog, which had occurred in the last summer, was also clearly observed in the winter of 1784, except on few days. It was seen in winter during snowfall, as it was always seen in summer during rainfall. From this coincidence we may conclude easily that this special vapour, which had caused extraordinary heat and disastrous thunderstorms in summer, was also responsible for the extraordinary amount of snow and extremely cold temperatures.

  This observer, of course, was pretty much spot on.

  The deep freeze was not restricted to Europe. The newborn nation of the United States also experienced an unusually hard and long winter, with the heaviest snowfall ever known in northern New Jersey, prodigious snowstorms in the south, and the longest recorded spell of below-zero readings in southern New England. Ice sealed Baltimore’s harbour on 2 January and did not release it until 25 March; at least three ships were lost. During the week of 10 February, temperatures in Hartford, Connecticut, fell below -24 degrees Celsius. There were ice jams in Virginia’s James River at Richmond and in the mouth of the Mississippi River, at New Orleans. Ice floes drifted in the Gulf of Mexico.

  In Pennsylvania, Henry Muhlenberg’s weather diary of 1783–84 is a litany of misery:

  December 24: Much snow and bitter cold.

  January 1: The New Year set in with an uncommonly deep snow, so that one can scarsely [sic] get out of the house.

  January 25: He could not get across the Schuylkill because the streams are too high and full of ice floes.

  January 29: Our children would be glad to be back home, but they must wait until there is a path made on the road, for the wind-storm has piled up the snow as high as six to eight feet in many narrow places on the road.

  February 7: The cold is so continuously severe that it is not to be compared with previous winters.

  March 9: Another deep snowfall… The dreadful winter is setting in afresh.

  In Virginia, the Bill of Rights author James Madison tried to make light of the snows in a letter to Thomas Jefferson:

  We have had a severer season and particularly a greater quantity of snow than is remembered to have distinguished any preceding winter. The effect of it on the price of grain and other provisions is much dreaded. It has been as yet so far favourable to me that I have pursued my intended course in law reading with fewer interruptions than I had presupposed.

  In typical didactic fashion, Jefferson tried to use the extraordinary winter to revive a plan to conduct simultaneous weather observations across the state. (He failed.)

  And in Mount Vernon, Virginia, the practical George Washington had his own complaints. Having reached his beloved plantation in time for the holiday season, hoping for a little rest and relaxation, Washington found himself ‘arrived at this Cottage on Christmas eve, where I have been locked up ever since in frost and snow.’

  Meanwhile, on the other side of the Atlantic, an old compatriot of Washington, Jefferson and Madison was himself shivering outside Paris, and wondering what to make of the sudden and chilling winter.

  CHAPTER SIX

  The Big Chill

  Laki’s global fallout

  IN 1783, BENJAMIN FRANKLIN was living in Passy, as the United States’ main diplomatic representative to France. Although Franklin had other weighty matters on his mind – notably, hammering out a British–American peace treaty following the Revolutionary War – he became fascinated, inevitably, by the oddities of the weather that summer. Franklin was many things – a politician, a writer, and America’s first postmaster. At heart, though, he was a scientist.

  No record exists of exactly when Franklin first spotted the dry fog that descended over France, but a key document survives that describes how he thought about it. In May 1784, Franklin sent a letter to his friend Thomas Percival, a physician in Manchester, who corresponded with him regularly on meteorological topics. The contents became public that December, when Percival read it in front of the Manchester Literary and Philosophical Society.

  Never one to let a natural phenomenon pass him by, Franklin had seized the opportunity to think about the mysterious haze. As usual, he had thoughtful and insightful things to say about where such a fog might have come from – things that cemented his reputation in the history of volcanology. In his letter to Percival, Franklin described the event:

  During several of the summer months of the year 1783, when the effect of the sun’s rays to heat the earth in these northern regions should have been greatest, there existed a constant fog over all Europe and great part of North America. This fog was of a permanent nature; it was dry, and the rays of the sun seemed to have little effect towards dissipating it, as they easily do a moist fog, arising from water. They were indeed rendered so faint in passing through it, that when collected in the focus of a burning glass, they could scarce kindle brown paper. Of course, their summer effect in heating the earth was exceedingly diminished. Hence the surface was early frozen. Hence the first snows remained on it unmelted, and received continual additions. Hence the air was more chilled, and the winds more severely cold. Hence perhaps the winter of 1783–4 was more severe than any that had happened for many years.

  Franklin was far from the only scientist to note the bitter winter of 1783–84, nor was he the first to link it to the dry fog that spread across Europe the previous summer. But in a typical Franklin twist, it appears as if he had been intrigued enough to try a little backyard experiment, to see whether the haze had attenuated sunlight to the point that a magnifying glass (a ‘burning glass’) could not ignite a fire. Such a minor test would not have been a stretch for a man who famously flew a kite into a thunderstorm to verify the nature of electricity.

  In his essay, Franklin goes on to probe where the dry fog might have come from:

  The cause of this universal fog is not yet ascertained. Whether it was adventitious to this earth and merely a smoke proceeding from the consumption by fire of some of those great burning balls or globes which we happen to meet with in our rapid course round the sun, and which are sometimes seen to kindle and be destroyed in passing our atmosphere, and whose smoke might be attracted and retained by our earth: or whether it was the vast quantity of smoke, long continuing to issue during the summer from Hecla [sic] in Iceland, and that other volcano which arose out of the sea near that island, which smoke might be spread by various winds over the northern part of the world, is yet uncertain.

  A curiosity for everything: Benjamin Franklin in Paris in 1783.

  Here Franklin proposes two ideas, one perhaps more outlandish than the other. The ‘great burning balls or globes’ he refers to are meteors, such as the fireball that soared across Europe on 18 August 1783. Richard Payne, a geographer at Manchester Metropolitan University, has argued that Franklin’s suggestion is the first time any scientist drew a link between an extraterrestrial impact and climate change.

  But Franklin has a second possible explanation for the dry fog: that it issued from a volcano in far-off Iceland. Franklin had never been to that exotic island, but if he thought a volcano might be to blame he would naturally think of the country with the mighty fire-mountains. Of those, Hekla was by far the most famous and among the most active, and so he proposed it as a possible source. But if Hekla was not the culprit, another possibility might be ‘that other volcano which arose out of the sea near that island’. That other volcano was Nyey (‘New Island’), a short-lived land that passing sailors had seen rising above the waves off Iceland’s southwest coast in the spring of 1783. Tales of its dramatic birth would have quickly spread to the continent, and in the absence of any information about the Laki eruption, Franklin was taking his best guesses as to which Icelandic volcano might have produced the menacing dry fog.

  Franklin was not alone in his surmises. Although he didn’t know it at the time, he wasn’t even the first to link the fog to Iceland. That honour probably belongs to French scholar Morgue de Montredon, who presented a paper about the dry fog to a learned gathering in Montpellier on 7 August 1783, more than half
a year before Franklin wrote his letter. Morgue de Montredon was a distinguished member of France’s national scientific society, and his paper is a detailed and careful summary of the extraordinary meteorological properties of the fog as seen around Montpellier. He concluded that the haze was rich in sulphur and suggested that it originated with a volcano. A volcano probably meant Iceland, and so de Montredon also picked Nyey as the likely source.

  Other scholars weighed in independently with similar ideas. Christian Gottlieb Kratzenstein, a physics professor at the University of Copenhagen, blamed the fog on Nyey sometime in the summer of 1783, and so may deserve the acclaim for being the first to link the haze to an Icelandic volcano. But de Montredon was the first to present his ideas in public, and he also had a greater impact among the scholars of continental Europe. Still, more than either of these two, it was Franklin who made the full link between volcanic activity and the ensuing cold winter. Richard Payne notes that unlike the others, Franklin went on to make a wider connection:

  It seems however worth the inquiry, whether other hard winters, recorded in history, were preceded by similar permanent and widely extended summer fogs, because if found to be so, men might from such fogs conjecture the probability of a succeeding hard winter, and of the damage to be expected by the breaking up of frozen rivers in spring, and take such measures as are possible and practicable, to secure themselves and effects from the mischiefs that attended the last.

  With such prescient words, Franklin’s essay brought the idea of a link between volcanoes and climate change into far broader public consciousness.

  The aerosols from Laki were lofted so high into the atmosphere that they spread not only across Europe but also, as we’ll soon see, across the rest of the northern hemisphere. To understand how Laki could have such a global impact, we’ll need to pause for a brief look at some basics of atmospheric chemistry.

  The part of the atmosphere that people experience every day – through which we walk, run, drive and fly – is called the troposphere. It makes up most of the mass of the atmosphere: four-fifths of all the nitrogen and oxygen and other elements that comprise the air we breathe is concentrated here. Weather patterns arise, evolve and expire in the troposphere. Most of humanity’s pollution also swarms throughout this lowermost layer.

  Now imagine being a balloon rising through the troposphere. As you get higher and higher, the air grows thinner and temperatures drop. Eventually, by the time you reach about -50 degrees Celsius, you get to a point where the temperature stops getting any colder. Now you’ve reached the top of the troposphere and are starting to move into a drier and more rarefied realm: the stratosphere.

  Some of the planet’s most important chemistry takes place in the stratosphere. For instance, here lies a layer of the triple-oxygen molecules called ozone, which shields the Earth from the sun’s searing ultraviolet rays (when not being depleted by man-made chlorofluorocarbon chemicals). More importantly for our story, the stratosphere is also where long-distance transport can happen. Any material in the atmosphere that makes it past the top of the troposphere and into the stratosphere can travel around the globe much more readily than it can lower down, where it would be washed out by rain and other everyday weather.

  So the boundary between the troposphere and the stratosphere is crucial. Get past that point, and you’ll be able to stay aloft much longer and travel greater distances. But here’s a complicating point: the boundary between those two atmospheric sections, known as the tropopause, varies in elevation depending on latitude. At the equator, the tropopause is typically about eighteen kilometres above the surface, whereas at the poles it is just eight kilometres up. (This difference is thanks to circulation patterns in the atmosphere, particularly jets of air known as the subtropical and polar front jets.) Therefore, gases and aerosols ejected by volcanoes at tropical latitudes, such as in Indonesia, have a lot further to go to reach the stratosphere. In contrast, those from volcanoes closer to the poles, such as in Iceland, have a shorter distance to travel and can more readily penetrate the stratosphere.

  Volcanoes eject many things – including ash, rock and gases – but the main factor that affects climate is the amount of sulphur. It initially billows out of volcanoes as sulphur dioxide gas, but within about a month this oxidizes in the stratosphere, or combines with other compounds, to form sulphuric acid. These acid vapours, along with water vapour, then condense into sulphate aerosol particles, which are the major player in volcanic climate change.

  Lower down, in the troposphere, rain washes out most sulphate aerosols within a matter of days. But particles that make it up into the drier stratosphere may survive for several years, plunging back down to the surface if they get mixed into descending air masses at mid-latitudes. They can also get sucked down through atmospheric vortices at the planet’s poles. Both processes take time, which means the volcanic particles can influence climate long after the ash plume has faded.

  Most eruptions never fire their aerosols high enough to reach the stratosphere, but those that do can affect climate in several ways. For one thing, the particles may warm the stratosphere by absorbing sunlight. They can also accelerate the rate of chemical changes, like the ozone depletion that happens when chlorine particles break apart ozone molecules. (Pinatubo’s 1991 eruption, in the Philippines, temporarily reduced ozone by as much as 20 per cent at certain layers in the atmosphere.) Most importantly, stratospheric particles can act as a giant sunscreen: they are just the right size to scatter incoming sunlight back into space, cooling the ground underneath as a result. In a general sense this observation is nothing new: after the 44 B.C.E. eruption of Etna, Plutarch observed how the haze of particles spewed from the eruption temporarily dimmed the sun. Modern science, though, has greatly improved our understanding of how this happens.

  A volcano’s climate-cooling power thus depends on two main factors: how high its gases are injected into the atmosphere, and how many sulphur aerosols are produced. Eruptions of around the same magnitude on the VEI scale can have very different climatic effects. The 1980 eruption of Mount St. Helens, for instance, had relatively little sulphur dioxide in its plume and cooled the planet very little, while the similarly sized El Chichón eruption in Mexico, two years later, cooled the planet quite a bit since it was so sulphur-rich. And that’s nothing compared to the sulphur giants. Pinatubo put about 20 million tonnes of sulphur dioxide into the stratosphere. But Laki spewed out more sulphur dioxide – about 122 million tonnes of it – than any other eruption in the past 1,000 years. That’s more than enough to wreak climate havoc well beyond Iceland and the rest of Europe.

  Just how much of the planet Laki affected is perhaps the biggest unanswered question about the eruption. There’s no doubt that the haze itself travelled far afield. Winds blowing toward the east spread it to Africa, the Middle East and beyond. By 1 July the dry fog masked the sky above central Asia’s Altai Mountains, some 7,000 kilometres from Iceland. It may have even spread to central China, as chronicles for that year from Henan province describe a ‘severe dry fog – sky is dark’.

  Whether the volcanic haze actually spread all the way to North America is controversial. Benjamin Franklin asserted that the fog had been seen over much of the continent, and a missionary in eastern Labrador reported that the air was:

  filled with the finest smoke so that the sun shone completely pale… It is now known to be sure that this smoky air which has occurred in the summer of 1783 over nearly all Europe, has found its origin at the earth fires in Iceland at which possibly the earthquakes at Calabria might have contributed… It seems this fog has occurred over the whole northern hemisphere, if not further.

  Few records exist, though, of any haze in northern American cities.

  Haze or not, Laki almost certainly did have an effect on North America. Tree rings in northwest Alaska show that trees packed on less wood in the summer of 1783 than in any other year for four centuries. Stories passed down among the Kauwerak people also suggest that a
disaster (the Inuit know it as the ‘time that summer did not come’) may have decimated the population around that time. One tale describes a woman who left her village full of the dead and journeyed with her baby for hundreds of kilometres along the coast, scavenging bits of roots and dried fish along the way until she found other survivors. The terrible summer is described as proceeding pretty much as usual until late June, when suddenly temperatures plunged, snow returned, and the ground froze all the way through to the next year’s spring. There’s no way to be sure this all happened in 1783, but it makes sense that the hard times would have occurred in the same year that local tree rings recorded dire environmental conditions.

  More controversial is the idea that Laki may have stretched its tendrils all the way to South America. In 2010, a Portuguese scholar reported that the astronomer Bento Sanches Dorta had recorded higher-than-average incidences of dry fog and haze in Rio de Janeiro in the autumn of 1784. ‘The months of September, October, and November were dominated by a certain kind of fog, or dense vapour, that obscured the Sun during the day and the stars by night,’ Sanches Dorta wrote. This haze might be traceable to Laki, which would make it the first record of any Laki impact in the southern hemisphere, but there’s little in the way of supporting evidence – and Sanches Dorta himself speculated that the fog came from a submarine volcanic eruption not far from Brazil.

  For modern scientists, the challenge is to understand exactly how Laki’s dry fog caused such dramatic climate change across the northern hemisphere. Overall, the Laki eruption emitted about as much sulphur dioxide as 12,000 coal-fired power plants do in a year. But not all of this climate-altering chemical spewed out at once: it came in pulses spread out over eight months, with most of it arriving during the first six weeks of the eruption.