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The sun also ices
The Little Ice Age: how climate influenced history, 1300-1850

By Brian Fitzgerald

It was a refreshingly cool subject on an unseasonably warm day. On October 24, when the temperature hit 80 degrees, renowned archaeologist Brian Fagan, a professor at the University of California at Santa Barbara, talked about chillier times: the Little Ice Age, a cold snap that lasted roughly from a.d. 1300 until as recently as 1850.

	Climate influencing art: snow dominates many villagescapes by Flemish painter Pieter Brueghel the Younger (1564-1638), who lived in the middle of the Little Ice Age.

For more than 500 years, the world was gripped in an Ice Age that caused famine and cultural dislocation. It wasn't one of the major glacial advances that lasted thousands of years -- those glaciations buried much of North America and Europe under a mile of ice. The last real Ice Age occurred some 10,000 years ago. But archaeologists and historians today use the term Little Ice Age for the period that saw turbulent, unpredictable, and often very cold weather.

Actually, "cold snap" is an oversimplification of what occurred. "By Little Ice Age, we don't mean a permanent deep freeze," said Fagan, recognized by many as America's leading writer on archaeology, in his talk to an audience of students and professors in the Stone Science Building. "It wasn't a period of extreme cold. It was a period of volatility in the weather, in which there were times of intense cold in the winter."

The harsh weather produced some rather bizarre scenarios. In the winter of 1780, New York Harbor froze, allowing people to walk from Manhattan to Staten Island. The ice was thick enough to bear the weight of even the heaviest cannons. In London, the freezing of the Thames River during the winters of 1683-84, 1715-16, and 1739-40 resulted in carnival-like "frost fairs" on the ice. In the mid-17th century, the glaciers in the Swiss Alps advanced -- the slowly flowing ice engulfed farms and crushed entire villages. By 1645, one glacier, the Mer de Glace (Sea of Ice) threatened the inhabitants of Les Bois. Then the bishop of Geneva performed an exorcism on the glacier, which retreated a few years later during a warming trend.

What caused the Little Ice Age? In his new book, The Little Ice Age: How Climate Made History, 1300-1850 (Basic Books, 2001), Fagan says that solar activity may have affected terrestrial climate. He points out that sunspots largely disappeared between 1645 and 1715. That period, called the Maunder Minimum, when the sun may have been about a quarter of one percent dimmer, matched one of the coldest spells of the Little Ice Age. But since the Little Ice Age lasted for more than half a millennium, the cooling must have had other causes. Volcanic eruptions are known to cool the climate by shooting sun-blocking aerosols into the atmosphere. The 1815 eruption of Tambora in Indonesia, for example, blanketed the atmosphere with ash and in 1816 caused what has been called the Year Without a Summer. In June and July of that year, frost and snowfall was reported in New England and Northern Europe. Other scientists point to El Niño and La Niña, the warmer and colder phases of a perpetual oscillation in the temperature of the Pacific Ocean that drastically affects weather around the world.

Brian Fagan talks about the hardships caused in part by the Little Ice Age. Photo by Kalman Zabarsky

Whatever the cause, the Little Ice Age devastated some societies. "The temperatures fell rapidly," said Fagan, describing the conditions that disrupted Norse trading in Greenland and Iceland. "The pack ice came south in the winter, and in the summer it didn't retreat." As a result, Iceland's population fell to half its previous numbers during the Little Ice Age. Numerous crop failures in Scotland and Norway are also attributed to this cooling. Before the Industrial Revolution, "Agriculture in Europe was profoundly marginal -- farmers literally lived from one harvest to the next," said Fagan. "In May of 1315, after the planting of the harvest, it started to rain. And it kept raining. The crops failed, and people started eating seed from the next harvest." The famine of 1315 killed more than 1.5 million people.

Fagan provided many snapshots of human suffering caused in part by the Little Ice Age: the Irish Potato Famine of 1847, shipwrecks in Scotland in July of 1596, punishing gales on the southeast coast of Ireland in July of 1695, the Paris bread riots in 1780. In his book he states that although the Little Ice Age partly accounts for such historical traumas as the French Revolution (the shortage of grain contributed), many of these events have social, economic, and political causes. But -- never underestimate the weather.

He pointed out that only in the last decade have climatologists developed an accurate picture of the Little Ice Age by looking at tree rings and ice cores for yearly temperature variations. But the technology is improving so much that "as of this year, they will have accurate tree ring data in northern and western Europe -- sufficient enough to give scientists yearly temperature and rainfall statistics as far back as a.d. 1500. In two years, they expect to have the data from as far back as Roman times."

Fagan was invited to speak at BU by CAS Archaeology Professor Norman Hammond because the subject is a case study of the impact of major climate change on a thriving civilization and may provide hints of how our society might handle a different episode of climate change -- global warming. "The devastating impact of the Little Ice Age, so clearly seen in the Norse abandonment of their toehold in the New World of Greenland, shows how even well adapted societies can be crushed by the juggernaut of climactic change, and how swiftly that change can occur," says Hammond. "As we ourselves impact the environment with greenhouse gases and other pollutants, we should consider how suddenly a viable world could be turned upside down."

2 November 2001
Boston University
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