The Great Warming tells the story of interactions between the Inuit and the Norse on the western shores of the Davis Strait that separates Greenland from the Canadian Archipelago during the Medieval Warm Period. Part of this story revolves around the Inuit's hunger for iron, which they obtained from Melville Bay in northern Greenland, as well as from the Norse. I recount the ingenious theory of Olaf Envig, who believes the Norse recycled nails from their worn out ships and traded them to the Inuit for walrus ivory. Like so many archaeological theories, this one depends on intangibles, for we are unlikely to find the places where the Norse recycled their ships or where they built new ones--perhaps in Labrador, if Envig is to be believed.

Smoked herring were a staple of medieval Europe

But there's another fascinating point here. Conventional wisdom has it that the Norse abandoned their Greenland settlements in the face of rapidly deteriorating climatic and ice conditions in the north. The bitter cold made their traditional dairying economy impracticable, and they resisted any notion of adapting Inuit hunting methods, especially ice fishing in the dead of winter. But a new generation of research is raising questions about the climatic theory. One of the staples of the Greenland Norse economy was walrus ivory, which was much prized in Iceland and Europe. Ivory was the major tithe paid to Norway by the Greenland church, as were furs and falcons. Greenland was the outermost frontier of Medieval Europe, difficult of access even in the more benign times of the Warm Period. This made its communities extremely vulnerable to shifting fashions in Europe. For instance, the soft ivory of the African elephant was ideal for carving, so much so that elephant tusks were an important part of the Indian Ocean dhow trade between India and Africa for many centuries. During High Medieval times, African tusks became more readily available in Europe, far more so than walrus ivory, at a time when ivory was used less frequently for icons and other religious ornaments. The demand for walrus dried up rapidly in the face of the new, softer material.

The shifting needs of the new fashions would have rippled out along Atlantic trade routes within a few generations. A lessening demand for walrus ivory may have come at a time when the Greenland climate was deteriorating, placing further stress on remote communities that often suffered through harsh winters. The twelfth to fourteenth centuries also saw a dramatic explosion in the European fish trade, centered on herring and cod, as new trade routes replaced ancient Norse networks. The Norse communities in Greenland finally withered away in the face of intense cold and economic isolation. So to invoke climate alone as a cause of Norse abandonment is probably tool simplistic an explanation--research continues.

Studying ancient climate change and human societies is rapidly becoming an academic bandwagon. Over the past few years, archaeologists, and historians, have discovered paleoclimatology with a vengeance, so much so that we’re in danger of going back to the old days of climatic determinism.

Back in the early twentieth century, the American geographer Ellsworth Huntington led a series of expeditions to Central Asia, which convinced him that climate change, and especially drought, was a primary cause of such major developments in the past such as the beginnings of agriculture. In many ways, Huntington was the last of the Victorian geographers, who were profoundly interested in the ways in which living organisms responded to their environments. Huntington’s simplistic doctrines have long been discredited, so much so that both archaeologists and historians shied away from climate change for generations.

Now climate change is fashionable again, largely because of the ongoing revolution in climatology, which has brought us cores, deep sea borings, and tree-rings that, thanks to European oaks, go back as far as about 10,000 years ago. Who would have imagined that a dating method, which provided the first accurate chronology for pueblo beams in the American Southwest, would allow us to date Dutch old masters, authenticate Stradivarius violins, and chronicle rainfall fluctuations down to the season over more than a thousand years?

The new fascination with ancient climate change ties in with a long, and on-going, search for explanations that goes back far earlier than Huntington. Why did humans take up agriculture and move into cities? How, why, and when did people settle in the Americas? The new, much more fine-grained data from tree-rings and ice cores has brought climate change to the fore front once again, as along-neglected factor in human history. From there, it’s a short step to specious arguments that are oddly reminiscent of Ellsworth Huntington’s extravaganzas, or even the relatively simple drought and oasis theories put forward by the European archaeologist Vere Gordon Childe in the 1930s that had humans, animals, and potentially domesticable plants gathered in oases at a time of drought.

Beware of simplistic explanations! Yes, climate change was a powerful factor in suchdevelopments as early agriculture, but many other things were also involved.Think of a pebble cast into a mirrorlike pond. With a plop, the pebble sinks to the bottom. Concentric circles radiate outward from the point of impact, gradually subsiding as they reach the banks. It’s these ripples, economic, political, and social, that are just as powerful as a prolonged drought or amajor El Niño cycle.

But it’s so easy to be seduced by the power of a drought or a series of major Nile floods. Fortunately, compared to Ellsworth Huntington, we know a great deal more abut ancient societies and the ways in which they adapted to external pressures of all kinds. And it was our humanity, our interactions with one another that tempered the effects of climate change.