Change is usually frightening, but appropriate response requires more than fear. Looking at the record, for instance…
…hath all to short a date. — Shakespeare, Sonnet 18
Fear has always been the major driver in environmental crises. Fear that the great mistake has been made at last, that nature has been pushed too far, that there is no dodging the bullet this time. Overpopulation, resource depletion, the long-term effects of pollution — all were unprecedented, their course unknown, the possibilities terrifying. Who could blame overreaction in dealing with them?
At first sight, global warming appears little different from earlier threats. The fears are certainly there, with new reports appearing almost daily: "Global Warming Has Helped Spread Disease," "Warmer Seas Breed Coral-Killing Virus," "Last Decade Hottest of the Millenium." (Nor has it been overlooked in SF, as any reader of Analog is well aware.) A major international treaty (the Kyoto Protocols) dealing with the problem has been signed (but not ratified by the U.S.). Fundamental changes are being suggested on all levels of the global order, with the approval of at least one serious presidential candidate. All this without the slightest recognition that climatic warming is not at all unprecedented, its effects by no means unknown, and its course far from disastrous.
There's a tendency to put climate in the same mental compartment as geology or astronomy: a continuum in which little or no change occurs in human or historical terms. Given that framework, any appreciable climatic shift takes on the character of a calamity, on the order of an earthquake or asteroid strike.
In truth, climate is weather writ long, subject to transitions and variations from a number of causes, a point adequately confirmed by the term "ice age". Or perhaps not so adequately, since the scale remains too vast. No small part of human history has been affected by climatic shifts, sometimes subtle, sometimes dramatic. These shifts are consistently accompanied by changes in temperature, one of the major climatic variables.
Since the end of the last glacial period, the Wisconsin State (or Würm State, as it's called in Europe) 6 to 7,000 years ago, Earth's climate has shifted repeatedly, with temperature variations looking (very) roughly like this:
Debate exists about details and dates. Some climatologists see a drought following the A.D. 300 warming, ameliorated by an increase in rainfall beginning around 800. In the absence of precise records, paleoclimatology utilizes "proxy measures" — pollen counts, ice cores, lake levels, the extent of peat bogs — to estimate average temperature. In North America, dendroclimatology, the examination of tree rings, has proven extremely accurate. In Europe trees are unreliable and instead glaciology, the study of glacier deposits, fills the role. The above record is derived from European glaciers (much of it from the Fürnau glacier in the Tyrol). While often enough different sources correspond, they're still estimates. All the same, no serious argument exists concerning the general outline across the centuries and millennia, including our chief point of interest, that last major warming episode, the Little Climatic Optimum (LCO).
Climatic conditions during the LCO were both milder and drier than today, with an average temperature increase of 1 to 2 degrees. (Two to four Fahrenheit — the scale we'll use throughout — in Greenland; a greater effect at higher latitudes, as predicted by several current warming models). Winter temperatures were up to 3.5 degrees higher, also suggested by current research. Warming appears to have been worldwide. There's no agreement as to cause, though there are plenty of theories, including a shift in Earth's axial tilt, changes in global wind cycles, passage out of a galactic dust cloud, and variations in solar output.
What were the effects? According to today's predictions, we'd find the Four Horsemen unbound: unusual and destructive weather patterns including more frequent and intense storms and longer, more severe droughts; rises in sea level; disruption of agriculture leading to famine; the stressing of local ecosystems, resulting in mass migration of animals (particularly insects); the extinction of marginal species; the introduction of new plagues.
The record shows otherwise. The major threat in the LCO didn't come from horsemen at all, it seems, but from men in boats.
During the LCO, ice effectively vanished from the northern seas, with icebergs rarely seen below the 70th parallel (roughly the line of the North Cape and Point Barrow). Weather underwent a general moderation, with storms few and feeble and seas tranquil. The resulting ease of navigation allowed northern routes to be crossed in craft little larger than lifeboats, not a trick you'd want to attempt today. (During World War II, Allied convoys cruising the same waters were oven saved from U-boat attacks by mountainous seas that prevented subs from closing.)
The Viking Movement has long enjoyed the status of legend: the early raids, the settlements and conquests, the new kingdoms, and most impressive of all, the discoveries. By the end of the first millennium the Vikings had explored the entire North Atlantic through private expeditions by tribes or families, an achievement excelled only by the Polynesians, sailing a very different and much calmer ocean.
Iceland, settled in 874, was the major Viking colony, serving as a base for expeditions further west. In 982, Erik "the Red" Thorvaldsson was exiled for killing a man and sailed from Iceland for an unknown landmass barely visible on the horizon on very clear days. (He had a bad reputation for that kind of behavior: he couldn't return home due to an earlier murder in Norway.) Accompanying him were his three sons, Leif, Thorvald, Thorstein, and one daughter, Freydis.
Three years later, Erik returned to Iceland to organize a colonizing expedition. In 986, he led fourteen ships and 250 colonists to found a settlement called Brattahild at Eiriksfjord on Greenland's southwestern coast. A second settlement soon followed. The colony wasn't much by our standards, though impressive for the medieval period. The population rose to 3,000 by the end of the 12th century, with 380 farms, twelve churches, a monastery, a nunnery, and a cathedral at Gardar.
It was the son of a Greenland colonist, Bjarni Herjolfsson, who actually discovered America. After going off course in a fog, he came across a flat, wooded shoreline the like of which he'd never before seen. For reasons known only to himself, Herjolfsson kept quiet for twelve years. (It's difficult to imagine why — Greenland lacked trees, requiring import of lumber for building. The last voyage to North America prior to Columbus in 1347 involved just such a lumber run.)
Leif heard of Bjarni's voyage while in Norway, and on returning to Greenland (either in 995-6 according to Farley Mowat, 1001-2 according to Samuel Eliot Morison, or 1003-4 in the Tale of the Greenlanders) mounted an expedition to the unknown shore.
Viking travels in North America can be traced thanks to a geological feature in Markland ("Wooded Land," modern Labrador) that Leif the Lucky called the Furdustrand ("Wonder Strand"), a beach of white sand bordered by dense woodland forty miles (Morison says thirty) long and in places 200 feet wide. The beach still exists, and references to it (along with several less impressive geological features) in the two pertinent Viking sagas reveal a fairly accurate itinerary. By this means, the major Viking settlement was located at L'Anse-aux-Meadows in 1960.
It was there that the Vikings found grapes. Some historians insist these were currants, gooseberries, or wild cranberries, anything to avoid admitting that grapes could have grown naturally so far north. (Another now-discredited school took them as evidence that the Vikings sailed further south than they actually did.) But their discoverer was a German named Tykir, who knew what grapes looked like. Nothing brings home the effects of warming more than the fact that Newfoundland was once called "Vinland."
Viking policy of killing anything they came across worked against them in the New World. The Skraelings ("screechers" or "uglies") were too numerous and, as many a settler was to discover in centuries to come, not overawed by the fighting abilities of the white man. It was the Indians, not the cold, that chased the Vikings out of Vinland the Good. The next wave of exploration five centuries later concentrated on the southern route, far from the ice and storms of the chilly North Atlantic.
Skepticism about the testimony of Serbs with battleaxes is easily excused. But the LCO was not a limited phenomenon, and records of its effects in Europe are, if anything, even more compelling than the sagas.
The Middle Ages are often viewed as an epoch of stolid peasants stumping back and forth with shouldered hoe, exploited by the nobility while the clerks look on. While this picture is still occasionally encountered in works such as William Manchester's A World Lit Only by Fire, serious studies of the High Middle Ages since the 1970s have revealed a different story: a Europe that was no stagnant backwater but the focus of two large-scale social advances — the European Agricultural Revolution and what may as well be called the First Industrial Revolution.
Little known outside professional historical circles, the European Agricultural Revolution is one of the key events in the history of the West, and by extension the human race as a whole. Centered on the fertile and unexploited northern European plains, utilizing new techniques, crops, and equipment, this revolution compeltely transformed the fundamental enterprise of raising foodstuffs.
For many years it was believed that introduction of the heavy plow, the nailed horseshoe, and the horse harness were the major factors in the new agriculture. But these were late developments. The key element was climate, specifically warming: "Progress in climatological studies in recent decades has led medieval historians to accept the fact that climate must have been one of the decisive factors in raising the level of agriculture."[*]
* Gimpel, P.32
Vinland had European counterparts. Vineyards were cultivated up to 300 miles north of their modern range, with England producing high-quality wines for export. Hills were plowed in Northern England that were too cool for cultivation even during the World War II emergency agricultural expansion.
Warming aided the farmer in a number of ways. Heightened temperatures caused forest lands to retreat, making clearance easier. Longer growing seasons encouraged earlier planting. Steady mild weather guaranteed larger and more certain harvests. Between the eleventh and thirteenth centuries the average European yield (the amount harvested for each measure sown) grew from 2.5 to 4, a figure not exceeded until the eighteenth century. In some areas of France that figure was doubled.
The security of generations of bountiful harvests moved the normally ultra-convservative peasantry to experiment not only with new gadgets but with novel forms of planting, including three-field crop rotation, and even new kinds of crops. The introduction of legumes — peas and beans — may sound less than exciting, but quite apart from broadening the nutritional base of the European population, the new foods also widened the culinary horizons of the common people. Today it's almost incomprehensible how monotonous the diet of the ancient world was. (Consider decades of lentils and bread — or rice — highlighted by the occasional chunk of ill-cooked meat. That was about it for most of humanity.)
The population of Europe rose from 27 million in the seventh century to 70 million in 1300. But the end of famine as a serious threat had subtler effects as well: "Accumulation of surplus food made possible population growth, specialization of function, urbanization, and the growth of leisure."[*]
* White, P.44
Another important consequence was a shift in the focus of European civilization beginning in Carolingian times from its ancient center around the Mediterranean to the northern marches of France and Germany. While many other effects were ephemeral, this was permanent; the cradle of Western civilization remained in the north even after the climate reverted.
Free time led to thinking and tinkering. The picture of the high medieval period as a whirl of technological change is also relatively new. Jean Gimpel, one of the pioneers of medieval technological studies, attributes this to the cultural gap between liberal arts scholars and grubby engineers, a situation not unfamiliar to Analog readers.
One of the benefits of the cultural shift to the north was the introduction of iron into everyday life from easily worked deposits in Germany. The smithy appeared in every village, the water mill in every town. Early advances were, naturally enough, those useful in agriculture. The inventions that followed, too simple to rise to the level of dullness but without which no industrial civilization can exist, include the compound crank, the connecting rod, and the flywheel. Higher-level devices followed: the turbine, the compass, the mechanical clock, eyeglasses. (Thanks to Fra Giordano of Pisa, who "…saw the man who disdcovered and practiced [the new art] and talked to him," we know to within a decade or so — 1270-80 — when eyeglasses were invented. But Giordano forgot to mention his name!)
The High Middle Ages were also the formative epoch of modern science, the age of not only the legendary Roger Bacon, but also his mentor Robert Grosseteste, the first chancellor of Oxford, who broke with classical precepts to insist that science be based on mathematics and experimentation, and Peter of Maricourt, who put that concept into practice as the first man ever to undertake a program of planned scientific research. The appearance of the Averroist school in the early 13th century, with its emphasis on the power of reason over authority, might have led to greater things had events not intervened.
At the same time — and this is no coincidence, since the processes that encourage mechanical ingenuity and the scientific worldview also underlie political and social evolution — medieval civilization saw the disappearance of slavery, the collapse of the manor system in favor of the small farmer, the emergence of the limited-stock company, the first stirrings of industrial capitalism. And with the decentralization of financial and political power came intimations of democracy. The warm years were crucial to the rise of the West.
Effects elsewhere were similar, if not as far reaching. In China, citrus orchards and warm weather herbs were grown further north than at any other time, reaching their greatest extent in the 13th century. In North America, the Anasazi civilization achieved its apex. The classic period of the Anasazi, 1100 to 1300, coincides almost exactly with the peak of medieval civilization.
All this thanks to a steady, pleasant climate? No — historically, there's no such thing as a single cause. If there's anything more complex than the natural world, it's human civilization. Potential had to exist in the first place. (Note that it was in Europe, not Song China or the American Southwest, that the pivotal social revolutions occurred.) But there are such things as basic elements, and few are more basic than climate. It's hard to imagine such a train of events occurring in anything but a steady, mild climatic environment. Earlier warming episodes bear this out: the Holocene Optimum coincided with the spread of agriculture across Europe, and Greek civilization peaked during a rare warm period (700-500 B.C.) in the long cooling that followed.
The essentially benign nature of warming is underlined by what happened when the climate turned sour. By 1200, cold was already curtailing shipping in northern seas. Icebergs returned and storms increased in both frequency and fury. The last Norse ship to land at Greenland circa 1408-1410 found a dying settlement, the cattle h erds vanished, the colonists eking out a meager existence from the few viable crops, the ice closing in. When English skipper John Davis arrived in 1585, he was met by Eskimos. (Also new arrivals, driven from the far north by the same cold that wiped out the Greenlanders.)
The final years in Greenland were no doubt much like what Iceland endured — terrible winters leading to famine, endemic disease, a population drop from 70,000 in 1100 to 34,000 in 1708, a consequent collapse of crude early democracy into oligarchy and monopoly. Iceland didn't fully recover until early this century.
In Europe the treeline fell 100 to 200 meters, the altitude for cultivating vineyards 220 meters. Harvests of all food-stuffs contracted, particularly those of fruits and grain. Much of this was due to an increase in rainfall. Beginning late in the 13th century, Europe was hit by storms brutal enough to flood large areas of coastline on both shores of the North Sea, including an entire Sussex port, Winchelsea, which disappeared beneath the waves in 1297. Within a few years the rains became general across Europe. In 1315 crop yields fell by a third, decreasing to half the next year. Grain prices were fixed by the king of France, which, as always, led to hoarding. The resulting famine of 1315-17 was the worst in centuries. (During the LCO, only three widespread European famines occurred, in 1125, 1197, and 1235.) Nearly 10% of the population of France and Flanders starved, with a comparable death rate elsewhere. So severe was the famine's impact that it triggered the medieval depression, which lasted for a century and a half.
Chronic hunger was a major factor in the next disaster, one of the great catastrophes of human history — the Black Death. Plague had vanished from Europe in the seventh century, retreating to its point of origin in Central Asia. Famine, and the resultant debilitation of immune systems, set the stage for a massive resurgence. It's seldom noted that there was a famine in northern Italy in 1347, the year before the plague struck.
As Barbara Tuchman has documented, the calamities of the fourteenth century had dire effects on the spirit: a shift toward the mystical and gothic, an obsession with death and decay, a retreat from the uplands of science and technology similar, though more extreme, to our own deluge of astrologers, pyramidologists, and witches following World War II. The dance of death. The witch hunts. The flagellants. (This last a direct response to the plague, born out of a pathetic conviction that if God saw men punishing themselves He would move to halt the disease.) The Church turning from its support of science and philosophy in favor of rooting out the "errors" of the Averroists and, for that matter, Roger Bacon himself. The popular image of the Middle Ages as dank, bleak, and obsessed with death and damnation arises from the years of the cooling, not the sunlit centuries that came before.
The balance of the millenium appears oddly frantic in historical terms, which probably only reflects our ignorance of earlier epochs. Climate slightly meliorated from 1350 to 1560. Then came the Little Ice Age (1560-1850), so-called due to the worldwide glacial advances. Glacier surges were at times so swift as to terrify onlookers. The Mer de Glace of Mt. Blanc was exorcised three times in an effort to halt its spread, once by no less than the Bishop of Paris. More practical was the foundation of the first weather services in the early seventeenth century. (Environmental panics are not exclusive to the modern era!)
The average temperature dropped 1 to 2 degrees. Permanent year-round snow covered northern Canada. Serious flooding occured in many areas, accompanied, paradoxically, by droughts in others. Drought may well have forced the Anasazi to abandon their great cities circa 1500, while the cold drove the Iroquois south from Canada.
Around 1850 a warming trend began, lasting until the late 1930s. It was followed by a mild cooling that peaked in the mid-1970s. Things have fluctuated since then.
One of the most heartening of all human attributes is the fact that we can learn new things from the past. Expanding knowledge illuminates not only ourselves but our ancestors as well. They accomplished more than they knew; recorded more than they understood. The Vikings were much more than ambitious marauders, the monks and clerks more than inspired tinkers. There's a lot we can learn from them, if only we care to look.
What we have learned from the Little Climatic Optimum is this:
* This includes such "canary" species as oceanic coral, alleged to be dying of contemporary warming. The coral of the Great Barrier Reef existed during the High Middle Ages and went through the LCO the same as every other species. It survived. Something else is bothering the coral.
The reasons why this vast pool of data has been overlooked are neither here nor there. It should be ignored no longer. The old mindset of "panic before thinking" has had its day. More research, both on the effects of the LCO and what it reveals about possible future warming, is imperative. Historical climatology remains an arcane discipline (apart from a strange volume on "climate and race" published in the 1930s only a single major book-length study exists, Ladurie's Times of Feast, Times of Famine, currently out of print). It deserves more attention from both the historical and scientific communities.
The most important point is that global warming is no catastrophe. There is no necessity for panic, despair, or ill-thought-out programs with massive price tags and hazy goals. We've been through it before, and we not only endured, we thrived.
But we may not be that lucky this time around.
The day I began work on the first draft of this article, it was 24° in central New Jersey; a bit cool for this 20th-century boy, much less a Viking. Three days later it was 10°. It remained in that range for the rest of January. At the same time vast and destructive storms — the worst in nearly a decade — pummeled the Mideast. Rainfall mixed with snow exceeded thirty inches in twenty-four hours in Lebanon, and winds of over fifty mph scoured Israel and Jordan. Similar storms knocked out power and brought transport to a standstill throughout Georgia and the Carolinas. It was a near encore of what had occurred exactly a year before — the worst storms in a century across central and northern Europe, those same plains that benefitted so vividly from the Little Climatic Optimum.
These are not epiphenomena of a warming trend. Nor is any of the "disrupted weather" of the past few years — hurricanes, droughts, unusual swoops and drops in rainfall. As we have seen, warming moderates the weather. Deteriorating weather is a result of global cooling.
In the excitement over rising CO2 and methane levels, one element commonly neglected in warming models (which treat its output as a constant) is the most important — the Sun. There's considerable evidence that cooling episodes are correlated with drops in solar activity, like the one that seems to have been occurring since the late 1950s…
But that's somebody else's article.
When not writing SF (This Side of Judgement, Days of Cain, and Full Tide of Night) J.R. Dunn is an independant historian working as associate editor of The International Military Encyclopedia. He is currently completing two novels and researching an expansion of this article to book length.
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