The Cold We Caused

by Steven Stoll

Harper's Magazine Notebook (November 2009)


It's not whether or not we're going through a global warming period. We were. We're not now. You know God's still up there. We're now going through a cooling spell. And the whole issue there was, Is it man-made gases, anthropogenic gases, carbon dioxide, methane. I don't think so.
-- Senator James Inhofe (Republican, Oklahoma), October 7 2008


Rather than continue to reject four centuries of scientific thought as an atheist conspiracy, skeptics of climate change now concede the effect and attribute the cause to a remote but still vaguely engaged Creator. For the nearly incoherent senator from Oklahoma - the ranking Republican on the Committee on Environment and Public Works - a March snowstorm in Tulsa proves that the Almighty has recently changed plans. Others of this cohort consult the Gospels on the future extent of flooding and call any suggestion of a human factor in global warming "arrogance". Senator Inhofe's humility would be philosophical if it weren't a charade meant to protect the economic system that is his real religion. Moreover, his tirades would be irrelevant but for the many citizens who agree with him. According to a poll by the Pew Research Center, 38 percent of those polled and 49 percent of white evangelicals believe either that climate change is a hoax or that humans are not responsible for it.

Inhofe might do well to ponder the recent discovery of one scientist at the University of Virginia whose findings amount to a natural experiment: What would happen to carbon dioxide and methane if humans disappeared? The answer is a tale not of drought but of rain, not of warming but of cooling. Its relevant technology consisted not of internal combustion and the steam engine but of horse collars and the moldboard plow. Excavate the Middle Ages, and one unearths a geological event with enormous implications for how we think about and respond to climate.

Alpine people told of glaciers crushing villages. The growing season throughout northern Europe suddenly shortened by two months. Torrential rains and flooding at harvest devastated crops repeatedly throughout northern Europe during the sixteenth and seventeenth centuries. Vikings arrived in Greenland late in the tenth century, at a time when they could plant wheat, but around 1350 the last residents ate their dogs before disappearing into the ice that had engulfed the southern tip of the island. As late as 1665, Norwegian wheat fields yielded just seventy percent of what they had produced in 1300. Cattle died on snow-covered pastures; wine and olive-oil production shifted south. A general sense of scarcity impelled agrarian people outward. Thousands of Europeans migrated to North America seeking relief, only to find the same impenetrable cold. Travelers and naturalists suspected for a century what geologists can now measure: the Northern Hemisphere fell into a frigid rut around 1350 that lasted until the nineteenth century.

This so-called Little Ice Age was not an ice age. The periodicity of ice ages follows long-term cycles in the position, relative to the sun, of Earth - the 100,000-year eccentricity of its orbit, the 41,000-year pendulum of its axis, and the wobble-like rotation it makes every 22,000 years. (This last to-and-fro, called precession, contributed to the most recent glacial maximum, known to us as the Ice Age.) On a graph these phases look like heartbeats on an EKG, except with a scale of hundreds of thousands of years. Glaciers heave and evaporate with pulsing regularity. Yet whereas the planetary physics of the Big Cold are fairly clear, that of the Little Ice Age are much less so. The latter came and went in a geological instant, too brief to have been caused by the wobble of Earth.

Although we think of carbon dioxide and methane as the exhalations of industrial production, air bubbles trapped in Arctic ice say otherwise. In fact, the increase started 8,000 years ago, with the proliferation of agriculture. Forests burned by humans, whether for fuel or to clear for planting, released tons of stored carbon. Three thousand years later, rice paddies and domesticated cattle began to let off methane, which traps heat twenty-one times better than carbon dioxide does. And yet temperatures barely changed during these eight millennia. But around 1400, gases and temperatures both plunged, then recovered, then plunged again after 1500. Atmospheric carbon declined by a statistically significant ten parts per million (ppm) in a period only slightly longer than a single human lifetime.

For decades, climate scientists have been unable to offer an adequate explanation for this drop. One geochemist has theorized that deep ocean currents flipped their distribution of warm and cold water, altering the heat exchange between atmosphere and ocean, though on closer inspection this looked more like an effect than a cause. The 1815 eruption of Mount Tambora, in Indonesia, injected 150 million tons of sulfuric ash into the atmosphere, blocking sunlight and creating "the year without a summer" - months of gloom and shadow, snow flurries across New England during June and July. But volcanoes cool for only a year or two. Sunspots, another suspect, follow an eleven-year cycle, and some geologists have favored them as a catalyst for the cold. But, like volcanoes, sunspots cannot possibly explain century after century of prolonged winter, and neither accounts for the missing ten ppm.


William Ruddiman, the environmental scientist at Virginia, has hit upon a solution to the riddle that is biological instead of geological. Even the best climate models, he realized, had ignored humans. Economic activity until the eighteenth century consisted of farming, hunting, handicrafts, and trading. To whatever degree these practices affected the global carbon budget, they did nothing to lower it. But Ruddiman saw that humans did something else during these centuries. They died in tremendous numbers.

The Little Ice Age coincided with a series of astonishing pandemics. The best documented began in October of 1347. Twelve galleys, heavy with trade from Caffa, sailed into the port of Messina, their Genoese crews groaning from sickness in the holds. At least one came ashore. The first Sicilian he greeted received a bacterial infection from a sneeze or a vaulting flea. A week later the Genoese sailor was dead, along with every Sicilian who had stood close enough to smell his breath. The afflicted buckled with fever and hard, bleeding ulcers: the first European victims of the Black Death.

Over the next four years, as many as fifty million people perished - representing half the inhabitants of Italy, the Balkans, Hungary, Lithuania, Germany, France, Spain, Ireland, Scotland, England, Norway, Sweden, Syria, and Palestine, as well as parts of Egypt, the Ottoman Empire, and Azerbaijan. So many Italians died so quickly that rotting corpses lay for days and weeks until the smell was unendurable. Entire families needed to be dragged to doorsteps so that undertakers could carry them away. "No tears or candles or mourners" ushered off the dead, wrote Boccaccio; "in fact, no more respect was accorded to dead people than would nowadays be shown toward dead goats". Bodies filled hasty trenches, "stowed tier upon tier like ships' cargo".

The social order unraveled. People became scarce. Peasants abandoned the manorial estates, leaving them without workers to sow or harvest. Wages increased due to the shortage of hands, and lords felt compelled to compete for workers by promising more money and greater freedom. One region in southern France did not regain the population it counted in 1300 for hundreds of years. Lands reclaimed by proliferating farmers in the eleventh century - mountainsides and wetlands - lost their human presence altogether. Ruined drainage canals on France's Mediterranean coast hummed with malarial mosquitoes. Wild game returned to the Massif Central (the upland plateau that borders the Rhone Valley to the east), including bears, boars, wolves, and partridges as thick on the ground as chickens. The aristocracy gave French peasants unrestricted hunting privileges in order to control the animal invasion.

Historians have toured this shattered landscape for centuries, on foot or in low-flying aircraft, from which buried fence lines and church foundations appear like impact craters. Yet by the time scholars discovered burial records and other evidence of the catastrophe, the living landscape yielded few clues. The human and animal populations had rebounded, leaving them no way of knowing that by 1400, woody growth had occupied at least 25 percent - and perhaps as much as 45 percent - of arable Europe. Birches and hazels squatted in the ecological real estate left vacant by human loss.

And the Black Death was not the only pandemic of the late Middle Ages. The same bacterium bad arrived in China a decade before, killing perhaps as many as fifty million. When Hernan Cortes invaded the Valley of Mexico in 1519, his armies brought smallpox, influenza, and mumps, setting off among never-before-exposed people a series of devastating infections that, as the diseases moved north and south, killed between fifty and sixty million over the following two hundred years. The destruction of life cut so deeply into Indian societies that many never recovered their earlier populations. These New World pandemics rolled on for centuries, causing a decline with greater implications for the atmosphere than even the European mortality. Globally, an estimated 125 million people died of pandemic disease between 1200 and 1750, representing 25 percent of the total population in 1500.

According to Ruddiman's hypothesis, the deaths of so many in such a short time, over terrain extending from the Po Valley to the Incan Empire, left hundreds of millions of hectares abandoned to reforestation. The rebounding woodland devoured 13.8 billon tons of carbon, accounting for more than half the missing ten ppm. The oceans ate the rest, probably as part of a feedback loop set off by the die-off. (Cold water stores more carbon dioxide than warm water, so falling temperatures would have created an ever more efficient carbon sink, leading to falling temperatures, before something broke the loop.)

How the Little Ice Age ended is perhaps even more revealing than how it began. As population lurched toward recovery, settler cultures felt the tension between lands and hands, sending ax-wielding farmers into the forests of Massachusetts, the Volga River Valley, and Manchuria. Between 1700 and 1920 the world's forests lost 537 million hectares, as agrarian societies increased their land use more than threefold. The carbon in all of those trees - together with soil itself, the greatest source on the surface of Earth - wafted up to thicken the eight-mile-high envelope that distinguishes this planet from Mercury. The world counted few coal-burning factories in 1850, but their numbers followed an accelerating curve as petroleum joined coal to provide the hydrocarbons that would generate two more centuries of economic growth. Under the new energy regime, atmospheric carbon levels rose by 100 ppm between 1750 and the present.


The Little Ice Age might seem to provide ideological fuel to our Inhofes, in that it shows an earlier and opposite shift in climate - an event that, moreover, lay beyond human control, like an earthquake or meteorite. In fact, however, this medieval tale reveals the enormous capacity of human beings to shape their environment, whether unwittingly or deliberately. If our crop-planting, animal-herding, forest-and- savannah-burning ancestors could trigger the rapid cooling of the atmosphere through their sudden absence, then we can achieve the same effect by abandoning other practices. The cold we caused does more damage to Inhofe's position than any finding by the Intergovernmental Panel on Climate Change.

But the significance of far-reaching events rarely lies where we please. Evangelizing environmentalists, much like evangelical Christians, have too often held humanity to an impossible standard, impossible for being imaginary. Some see Earth before agrarian humans as an Arcadia against which we can assess the sins of industrial society. The world without us, in this view, would return to its true temperature, its steady state. Growing up as a species, however, means accepting that we are neither blessed by Heaven nor shatterers of the natural order. No such order exists: no true or natural climate, no normal rate of extinction, no ideal ecology. The only thing normal about climate is its propensity to slam back and forth between, maxima and minima, between infernal winters and refrigerated summers. In the oscillating dance of the glaciers, species die. Whether they die from meteorites or from billions of human decisions makes no difference. Either way, they leave behind abandoned niches - the ecological spaces organisms inhabit - resulting in evolutionary cascades of new species. Everything alive is matter in one momentary form, soon to take some other momentary form.

The Little Ice Age negates the notion of a pristine planet, insisting instead on a more clearly defined place for humans in the grand narrative of Earth's history. In 2000, the chemist Paul Crutzen named our current era the Anthropocene, a period in which humans figure on a geological scale. But whereas many date the Anthropocene to the advent of coal-burning machines, Ruddiman's work lengthens the period to begin when the first stick plow cut the first furrow. It was the invention of agriculture that marked the beginning of the Anthropocene, because that was when terrestrial environments and atmospheric chemistry became artifacts of human culture; when our imprint on the climate became like fossilized footprints in volcanic ash. The Anthropocene has been an era of extinction to rival that of the Cretaceous, and will be defined by the present moment, when our demonstrable power to foster or erode the diversity of life can no longer be handed over to God or Nature.

During the nineteenth century, American naturalists and politicians denied that any animal ever had or ever could become extinct. Confronted by evidence of the eradication of the passenger pigeon and the near destruction of the bison, the deniers developed absurd theories to explain away the obvious: that decades of intense commercial hunting had wiped out or endangered countless species. Today, at stake in the denial of climate change is the extinction or impediment of billions of the world's poor. One billion now live in slums - a number increasing every day and soon to surge as rising sea levels cause others to become environmental refugees. The impoverished cannot afford the higher cost of food when coastal land ceases production. They will have to move when wells and rivers dry up. Once we accept the human capacity to reconfigure the climate, the rich nations will become directly responsible for the suffering of the poor. The litany of rationalizations regarding the global poor - including their own low morality, a punishing God, and the Darwinian workings of the market - might finally buckle and break once the very poor file class-action suits against the wealthy nations for reckless carbon output.

Taking responsibility for the consequences of agriculture, capitalism, and industrialism is not the same thing as believing that humans control the tilt and wobble of the globe. It requires us to wield what control we have through public policy. The recent decision by the Environmental Protection Agency to regulate greenhouse gases as a public-health risk under the Clean Air Act does more than rebuke the deniers. It represents an extraordinary shift in American perception. It heralds the end, or so we can hope, of an approach to our atmosphere - as an infinite sink - that has financed industrial capitalism since soot turned the birds black in Manchester. We can only hope that the people of the most polluting nation will finally ask some meaningful questions. What is a just climate and what an unjust one? Which climate represents the insatiable demands of corporate growth rather than the health and stability of everyone else? By confirming the human role in climate change, and by declaring a warming world injurious to the public good, the EPA has swung a club against perhaps the grandest capitalist conceit of the twentieth century: that society forms part of the economy, not the other way around.

Ecology becomes policy when our responsibility becomes undeniable. So completely cultivated, walked over, and settled up is our planet that it no longer makes sense to regard any part of it as lying beyond human influence. To paraphrase Stewart Brand, we are the climate, and we might as well get good at it.

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Steven Stall is an associate professor of history at Fordham University and the author of The Great Delusion: A Mad Inventor, Death in the Tropics, and The Utopian Origins of Economic Growth (2008). His last article for Harper's Magazine, "Fear of Fallowing", appeared in the March 2008 issue.


Bill Totten http://www.ashisuto.co.jp/english/index.html