Bridge is published by the Boston University Office of University Relations.
sun also ices
The Little Ice Age: how climate influenced history, 1300-1850
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.
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 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.
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