Fagan - The great warming: climate change and the rise and fall of civilizations

The Great Warming

CLIMATE CHANGE AND THE
RISE AND FALL OF CIVILIZATIONS

Brian Fagan

BLOOMSBURY PRESS
NEW YORK BERLIN LONDON

To
the Great Cat of Ra and the Venerable Bede
Black-and-whites extraordinary

__________________

All right, said the Cheshire Cat; and this time it vanished slowly, beginning with the end of the tail, and ending with the grin, which remained some time after the rest of it had gone.

Lewis Carroll, Alices Adventures in Wonderland (1865)

Contents

My name is Ozymandias, King of Kings,
Look on my works, ye Mighty, and despair!
Nothing beside remains. Beyond the decay
Of that colossal wreck, boundless and bare,
The lone and level sands stretch far away.

Percy Bysshe Shelley, Ozymandias (1812)

THE GREAT HOUSE, PUEBLO BONITO, stands gaunt and silent, nestling under the precipitous cliff, the serried rooms open to the gray sky. A chill wind scatters dead leaves and delicate snowflakes across the empty plaza on this bleak winter day. Clouds hang low over the cliffs of Chaco Canyon, New Mexico, swirling in the gusts of the January storm. The silence is complete.

A thousand years ago, Pueblo Bonito was a sacred place, which echoed to spectacular dances at the summer solstice. Visitors from miles around flocked to this, perhaps the greatest of all southwestern pueblos. Then, in A.D. 1130, fifty years of drought sank over Chaco Canyon. Maize yields plummeted. Within a few years, Pueblo Bonito emptied. Half a century later, Chaco Canyon was virtually deserted. After many centuries within the canyon walls, the Ancestral Pueblo had moved away and settled with relatives living in better-watered areas.

This winter day, no ghosts of a thousand years ago rise to haunt my imagination and excite my consciousness. The past is dead, long vanished into oblivion. Im reminded of Shelleys Ozymandias, King of Kings, his deeds forgotten, his palaces reduced to crumbling ruins.

In A.D. 1118, a decade before the great drought arrived at Chaco, the Khmer god-king Suryavarman II ascended to the throne of Angkor on Cambodias Tonle Sap in Southeast Asia. Almost immediately, he began building his masterpiece, Angkor Wat. Thousands of his subjects labored on his palace and temple, a vast replica of the Hindu universe, complete with sacred mountains. Nothing mattered but to serve the god-king. Suryavarman and his successors created a centripetal religious utopia erected on a foundation of intensive rice cultivation, irrigated with canals, reservoirs, and flooded paddies nourished by the summer flood.

Angkor Wat no longer boasts gilded towers and brilliantly painted temples. But it still mesmerizes, with its maze of stairways and long, echoing galleries adorned with yard upon yard of royal processions, armies on the march, and sinuous dancing girls promising the delights of paradise. Then you realize that the place is lifeless, a moment frozen in time, abandoned by its builders when in full magnificence, partly because drought dried up their rice paddies and they went hungry.

Again, Ozymandias comes to mind. Angkor Wat leaves you with a sense of futility and despair.

Chaco Canyon and Angkor Wat are silent testimony to the power of climate to affect human society, for better or worse.

Soon after Suryavarmans loyal subjects labored on Angkor Wat, the cathedral of Notre Dame de Chartres rose in northern France. Built in a mere sixty-six years after A.D. 1195, this Gothic cathedral was the sixth church on the site, a miracle in stone and glass. Like Angkor Wat, Chartres is a masterpiece, but this ones still part of the fabric of human life, a place where masses are celebrated and psalms chanted. Here the infinite becomes a miracle in stone and glass. Chartres is all windows, set among soaring beams and graceful arches. Gemlike sunlight shines through them, creating transcendental effects. The setting still brings heaven to earth and links the secular and the spiritual, just as it did a thousand years ago. Here the past is still alive.

Chartres was built at a time when Europe basked in a warmer climate and enjoyed a long series of good harvests. Those who benefited thanked God and the unknown powers of the cosmos for their bounty. They built a cathedral in gratitude.

The world of a thousand years ago was a vibrant, diverse place, much of it a tapestry of volatile civilizations, great lords, and endemic warfare. Camel caravans, the Great Silk Road, and monsoon winds connected much of the Old World in the first iteration of a truly global economy. However, most humans still lived in small hunting bands or as subsistence farmers, surviving from harvest to harvest, eking out a living from the soil. We have long known of this world from archaeology, from excavations into great cities, into caves and humble shell mounds, and from scatters of Norse iron nails in the High Arctic, from historical documents and oral traditions. But its only now that were learning just how profoundly the warmer climate of the day affected humanity. This book is the story of five centuries of changing climatein fact, of a global warmingbetween A.D. 800 and 1300, and of the changes impact on the world of a millennium ago. As in our own time, climate change did not plot a straight line from year to year, and varied from place to place. But its peaks and valleys followed a trend that we can clearly make out in retrospect. We have much to learn from this story about the power of climate change to affect our own future.

THE MEDIEVAL WARM Period was named half a century ago by a British meteorologist, Hubert Lamb. He wrote of an era from about A.D. 800 to 1200 that he pieced together from a jigsaw of climatological and historical clues: four or five centuries of relatively amiable climate that brought good harvests to Europe and permitted the Norse to land in Greenland and North America. The Medieval Warm Period gave way to six centuries of highly unsettled climate and cooler conditions: the Little Ice Age.

We have long known many details of the better-documented Little Ice Age, when, famously, the Thames River froze over. There were famines and severe tempests, occasional winters of exceptional cold. But the Medieval Warm Period was, until recently, a climatological mystery. Lamb wrote at a time when paleoclimatology, the study of ancient climate, was in its infancy, and long before humanly caused global warming was on the scientific radar. Today, we know a lot more about the Medieval Warm Period than he did. Thanks to tree-ring research, we now have detailed information on seasonal rainfall and temperatures in Europe and in the North American Southwest going back at least a millennium. In the chapters that follow, sidebars will discuss some of the methods we use to study prehistoric climate. Ice cores from Greenland, also from high in the Andes and elsewhere, provide important data on cooler and warmer cycles over the past two thousand years. Growth layers in tropical coral from small Pacific atolls also document climatic shifts over many centuries. And tree-ring sequences from around the world are slowly putting flesh on the Medieval Warm Periods still-shadowy skeleton.

Europeans built cathedrals and the Norse sailed to North America during the Medieval Warm Period, but the picture of the warm centuries thats emerging from the new research depicts a climatic villain as much as a hero. There was indeed warming, in most places reflected in milder winters and longer summers, but the temperature differences never amounted to more than a few degrees. Nor was everywhere necessarily warmer. In the eastern Pacific, the same centuries were cool and dry. These were times of sudden, unpredictable climatic swings, and, above all, of drought. Extended medieval dry cycles helped topple Chaco Canyon and Angkor Wat, contributed to the partial collapse of Maya civilization, and starved tens of thousands of northern Chinese farmers.