Warming or Cooling?

Published December 1, 2000

It was AD 986. Erik the Red, ousted from Iceland for manslaughter, set sail with a hardy group of Vikings for a faraway land. Erik called it Greenland, a place ordinarily hostile to humans with its mile-thick ice cap. Erik’s improbable mission succeeded. The Norsemen established two communities on the southwest coast of Greenland, where they raised livestock on 280 farms. Later, they even sent expeditions west to explore Vinland (Newfoundland). They made history.

What Erik could not have known was that his adventure, like other Viking exploration a thousand years ago, was greatly aided by a long-term change in the weather. For about 400 years, much of the Earth’s climate inexplicably warmed—a period we now know as the Medieval Warm Period. Temperatures may have averaged 2 to 3 degrees C higher than they are today.

The Medieval Warm Period was just one phase of this millennium’s highly variable weather. First, it was wonderfully warm. Then, it got terribly cold. And today, it seems to be warming again.

This changing pattern played a pivotal role in the history of the millennium. As it warmed in the early years, the weather helped farmers raise more bountiful crops and encouraged mothers to have more children. Explorers like the Vikings sought out new lands, and prosperity encouraged the building of cathedrals. Mountain glaciers receded in Europe.

Sea ice off the coast of Iceland nearly vanished for three centuries. The effects seem to have spread to North America, where in AD 900 Eskimos settled Ellesmere Island at the usually frigid northwest corner of Greenland. In Alaska, a warming trend was detected. And in the Rocky Mountains, the new warmth pushed the snow line about 1,000 feet higher than where it stands today.

Then a chill set in. Slowly at first. People didn’t want to believe it. Farmers were reluctant to give up their new fields. Settlers on Greenland held on for as long as possible. But the steadily expanding cold was irresistible by the 1200s. Unspeakable hardships began to take hold in much of the world.

In Iceland, extensive grasslands that had supported sheep, goats, and cattle from AD 874 had receded by 1200. Farming became so difficult that Icelanders turned to fishing and the hunting of seals to support themselves. The population fell sharply.

By the late 1500s, temperatures continued to plunge, and the Little Ice Age firmly gripped much of the world. Life changed for millions of people. In Europe, there was immense suffering. Crops failed. The poor grew poorer. Infanticide and abortion increased as families ran out of food. Several Eskimos, driven south by ice, paddled as far as Scotland. The Thames River at London froze frequently in the 1600s. “Frost fairs” atop the Thames became common in the 1700s, and in 1820 it was so cold the river ice was reported as five feet thick.

By 1700, Iceland was surrounded with sea ice that made commerce with the rest of the world hazardous. And in faraway China, citrus groves that had survived for centuries froze in Jiangxi province.

The Little Ice Age lasted anywhere from 400 to 700 years. Exact dates are uncertain. There were no thermometers during much of this period. Some suggest it didn’t end until around 1900.

Reprinted from The Christian Science Monitor, for which John Dillin is a staff writer.