by Brian Fagan
Another solar phenomenon may also be at play. A group of astronomers and climatologists has studied solar "corona," literally holes in the sun's outer atmosphere through which streams of charged particles flow into space to engulf the entire planetary system. They believe this solar wind activity has a direct connection to climatic change on earth: charged particles hitting the earth's atmosphere affect the properties of clouds and the percentage of them covering the globe. When numerous coronae cover the solar surface, the increased solar winds produce greater terrestrial cloud cover, and average temperatures drop. The importance of this effect is still unknown.15
Solar radiation is never constant, making it a possible cause of climate change, and a factor in the current warming. Over the past twenty years, space-based measurements of solar radiation, the first accurate data on these fluctuations, have revealed eleven-year cycles that correspond to the well-known eleven-year cycle of sunspots. Solar intensity is greater at times of higher sunspot activity. Proxy measurements from tree rings and ice cores chronicle these cycles and longer term fluctuations in earlier centuries. We know solar activity was high during the twelfth and thirteenth centuries, the height of the Medieval Warm Period. Present levels of solar irradiance are higher than periods of unusually low sunspot activity during the Sporer (1425-1575), Maunder (1645-1715), and Dalton Min ima (1790-1820). Solar activity increased steadily during the first half of the twentieth century but has changed little since 1950, beyond the usual eleven-year cycles. In computer climate simulations, the surface temperature warming resulting from the known fluctuations in solar radiation between 1600 and the present amount to only 0.45°C. Less than 0.25°C can be attributed to the period 1900 to 1990, when surface temperatures rose 0.6°C.16 Changes in solar radiation appear to account for less than half of twentieth-century warming.
Solar activity is currently at a high level relative to the record of the past 8,000 years, which suggests that future impacts of solar radiation on global climate will be much smaller than those stemming from greenhouse gases. Even during sunspot minima, reduced solar luminosity probably accounted for no more than half a degree Centigrade of cooling. Solar radiation is large enough to shape global warming, but not to dominate it.
Even if the sun does significantly influence climate change on earth, humanly generated greenhouse gases, virtually absent during the Little Ice Age, are almost certainly the major agents of the current sustained warming. Prudence suggests that we plan for an entirely new era of climate change.17
What form will this change take? One school of thought, popular with energy companies, is serenely unfazed by global warming. Gradual climate change will bring more benign temperatures. Sea levels will rise slightly, there may be some extreme weather events, but within a few centuries we will emerge into a more uniform, warmer regimen of shrunken ice sheets, milder winters, and more predictable weather-much like earth in the time of the dinosaurs. Humanity will adjust effortlessly to its new circumstances, just as it has adjusted to more extreme changes in ancient times.
The record of history shows us that this is an illusion. Climate change is almost always abrupt, shifting rapidly within decades, even years, and entirely capricious. The Little Ice Age climate was remarkable for its rapid changes. Decades of relatively stable conditions were followed by a sudden shift to much colder weather, as in the late seventeenth century, 1740/41, or even the 1960s. The same pattern of sudden change extends back as far as the Great Ice Age of 15,000 years ago, and probably to the very beginnings of geological time. Given this history, we would be rash to assume that sudden climate change will miraculously give way to a more uniform warming trend. The exact opposite seems more likely. In all probability the dinosaurs lived through short-term climatic shifts that were just as unpredictable as those of the past 10,000 years, if for no other reason than that large-scale volcanic activity was just as prevalent then as it is today. The Little Ice Age reminds us that climate change is inevitable, unpredictable, and sometimes vicious. The future promises exactly the same kinds of violent change on a local and global scale. If the present, unusually prolonged high mode of the North Atlantic Oscillation is indeed due to anthropogenic forcing, then we must also assume that global warming will accentuate the natural cycles of global climate on the largest and smallest scales. Some of these potential cycles of change are frightening to contemplate in an overpopulated and heavily industrialized world.
This concern has ample historical precedent. Eleven thousand years ago, long before the Industrial Revolution, humanity experienced a fast climate change that came as a complete shock. After some three millennia of global warming, rising sea levels, and shrinking ice sheets at the end of the Great Ice Age, a massive influx of fresh glacial meltwater into Arctic waters shut down the downwelling that carried salt water into the deep ocean. The warm conveyor belt that had nourished natural global warming in the north abruptly stopped. The warming itself ceased perhaps within a few generations, plunging Europe into near-glacial cold for a thousand years. Glaciers advanced, pack ice spread far south for much of the year, and forests retreated southward. Rainfall zones shifted, and intense drought settled over southwestern Asia, causing many Stone Age bands to turn from foraging to farming. The millennium-long "Younger Dryas" event, named after a polar flower, ended as rapidly as it began, when the downwelling switch abruptly turned on again and warming resumed.
Younger Dryas Europe was sparsely populated by hunter-gatherer groups that were mobile enough to adapt to rapidly changing environmental conditions. What would happen today if northern downwelling were to slow down or cease and plunge Europe into near-glacial cold? Anthropogenic global warming could easily flip the switch. Models of ocean circulation patterns hint that even a modest increase in fresh meltwater inflow into arctic seas could choke off downwelling in the North At lantic. The pulse of fresh water would float atop the dense, salty Gulf Stream, just as it did 11,000 years ago, forming a temporary "lid" that would effectively prevent the Gulf Stream water from cooling and sinking. A sea ice cap could form in short order, preventing the Gulf Stream from starting up again, and trigger an intensely cold regimen in Europe within perhaps a few years. No one can predict how long such a cold snap would last. A few unusually warm summers might melt the ice and expose the Gulf Stream, allowing downwelling to resume and milder climate to return. Or evaporation of water vapor in the tropical Atlantic far from the ice sheets could cause such a buildup of salt water that downwelling would begin at the edges of the ice zone, far from the traditional spots, again causing a rapid warmup of European climate.
The consequences of a Younger Dryas-like event to industrial agriculture alone, though truly frightening to contemplate, are not beyond the grounds of possibility. The chance is remote, but Europe's planners factor it into their scenarios for the climatic long-term future.
The short-term climatic future is relatively easy to predict. If warming continues on its present trajectory, growing seasons in Europe will lengthen, vineyards will again be established in central England, and farms will be cleared closer to the Arctic Circle. Northern Europe and much of North America may prosper from the warmth, but southern Europe, much of tropical Africa, and Central and South America will suffer more frequent water shortages and greater heat, as well as diminished agricultural capacity. Confrontations over water rights will flare in countries like Egypt, which depend on river flow from across national borders. People will adapt as they always have, but drier tropical regions with at least 400 million people subsisting in overpopulated marginal environments will make that adaptation difficult.
What of the longer term, if global warming accelerates? Sufficient reserves of fossil fuel exist to cause a continued growth in atmospheric carbon dioxide levels well into the twenty-second century. If this growth continues unchecked, the climate changes on earth will probably be very large indeed and extremely unpredictable. But many scientific uncertainties remain. Recently, James Hansen and a group of his colleagues have a
rgued that the rapid warming of recent decades has in fact been driven mainly by non-CO2 gases such as chlorofluorocarbons. Fossil fuel burning CO2 and aerosols have both positive and negative climatic forcing effects, which tend to cancel each other out. Hansen and his team point out that the growth rate of non-CO2 gases has declined over the past decade and could be reduced even further. This, combined with a slowing of black carbon and CO2 emissions, could lead to a decline in the rate of global warming.18 Much more research is needed to confirm this hypothesis.
Optimists assume that we will adapt comfortably. We humans do have a striking ability to adapt to changing environmental circumstances at the local level. Witness the agricultural revolution in Flanders, the Low Countries, then Britain during the climatically unpredictable sixteenth and eighteenth centuries.
Yet optimism fades in the face of demographic reality. Six billion of us now inhabit earth, with hundreds of millions still subsisting from harvest to harvest, from rainy season to rainy season, just as many European peasants once did. For Europe and North America, with their industrial-scale agriculture and elaborate infrastructures for moving food over long distances, famine is remote. But subsistence farmers on other continents still live with the constant threat of hunger. As I write this, more than 2 million cattle herders in northeast Africa face starvation because of severe drought. Such numbers are hard for us to comprehend in the prosperous West. They will become still harder to comprehend if global temperatures rise far above present levels, when rising seas inundate densely populated coastal plains and force millions of people to resettle inland, or far more severe droughts settle over the Sahel and the less well watered parts of the world? I have avoided discussing wars in this book-it would be simplistic to say that wars or other complex political events were caused by climatic change-but it's implausible to suppose that famines and massive dislocations of poor populations will be unaccompanied by civil unrest and disobedience. We can only imagine the potential death toll in an era when climatic swings may be faster, more extreme, and completely unpredictable because of human interference with the atmosphere. The French Revolution or the Irish potato famine pale into insignificance.
Even if the present warming is entirely of natural origin, greenhouse warming in the future could be accentuated by fossil fuels. We would be rash to ignore even theoretical scenarios, for we and our descendants are navigating uncharted climatic waters. In that respect we are no different from medieval farmers or eighteenth-century peasants, who took the weather as it came. Today we can forecast the weather and model climatic change, but globally we are still as vulnerable to climate as were those who endured the famine of 1315 or the great storms of the Spanish Armada, simply because there are so many of us and we are so closely linked, environmentally, economically, and politically. Fortunately, we now have, or will shortly have, the scientific data that document the full extent of the danger. We also know what has to be done, and have many of the tools to make significant changes. But to implement countermeasures to reduce greenhouse gasses and minimize the impact of climatic extremes on an increasingly crowded world community will require a new altruism, and a desire to work for the global rather than the national good, for the welfare of our grandchildren and great-grandchildren rather than to satisfy short-term, often petty, goals. Political bickering, selfish national interests and the intense lobbying of international business have so far militated against broad agreement as to the path ahead.
Over a century ago, Victorian biologist Thomas Huxley urged us to be "humble before the facts." The facts stare us in the face, yet we do not display sufficient humility. As British diplomat Sir Crispin Tickell recently remarked: "Mostly we know what to do but we lack the will to do it."19 The vicissitudes of the Little Ice Age remind us of our vulnerability again and again. In a new climatic era, we would be wise to learn from the climatic lessons of history.
The literature surrounding the Little Ice Age is diffuse, enormous, and profoundly contradictory, much of it in extremely obscure, specialized journals. To fully reference this book would festoon it with hundreds of footnotes. Instead, I have elected to provide a guide to further reading among the citations, footnoted at a general level to the text. The reader will find comprehensive bibliographies in most of the works cited below, which will provide an entry into the technical literature.
PREFACE
The quote from George Philander is from Is the Temperature Rising? (Princeton: Princeton University Press, 1998), 3.
PART ONE WARMTH AND ITS AFTERMATH
The Chaucer quote is from the Canterbury Tales, edited by John Coghill (Baltimore: Pelican Books, 1962), 17.
The German chronicler of 1315 is quoted in William Chester Jordan's The Great Famine (Princeton: Princeton University Press, 1996), 20.
CHAPTER 1
The excerpt from Hafgerdinga Lay ("The Lay of the Breakers") is quoted in Magnus Magnusson and Hermann Palsson, eds., The Vinland Sagas (Harmondsworth, England: Penguin Books, 1965), 52.
1. H. H. Lamb, Climate, History and the Modern World (London: Methuen, 1982), 165. Lamb's work is an excellent, thorough summary. M. L. Parry, Climatic Change, Agriculture, and Settlement (Folkstone, England: Dawson, 1978) covers expansion and contraction of agricultural activity, especially in Scotland.
2. Both quotes in this paragraph from Jean Grove, The Little Ice Age (London: Routledge, 1988), 21-22. Grove's monograph is one of the few book-length studies of the Little Ice Age and is seminal, if, inevitably, outdated in places. Hermann Flohn and Roberto Fantechi, The Climate of Europe: Past, Present, and Future (Dordrecht, Germany: D. Reidel, 1984) offers another technical analysis.
3. Magnusson and Palsson, The Vinland Sagas, 78.
4. Kirsten A. Seaver, The Frozen Echo: Greenland and the Exploration of North America, ca. A.D. 1000-1500 (Stanford: Stanford University Press, 1996), 46. This work is an authoritative study of the early settlement of the north during the warmer centuries. For the Vikings generally, see the lavishly illustrated volume: William W. Fitzhugh and Elisabeth A. Ward, eds., Vikings: The North Atlantic Saga (Washington, D.C.: Smithsonian Institution Press, 2000).
5. The term "Gothic" was coined by Renaissance scholars, who considered the style the epitome of grotesque savagery. Subsequently, contempt has turned to admiration and near adoration.
6. Until the eighteenth century, farmers were described with a variety of terms that denoted their status in the community rather than their occupation. In the sixteenth century, for example, most people were engaged in some form of farming as well as other occupations at the same time. For instance, almost all country clergymen were farmers, since much of their living came in the form of land. Craftspeople, miners, and many other combined these occupations with seasonal work on the land. For the purposes of this book, I use the term farmer generically, as the context of its use is usually obvious.
7. Norman Davies, Europe: A History (New York: Oxford University Press, 1996), 356. John Mundy, Europe in the High Middle Ages, 1150-1309, 2nd ed. (New York and London: Longman, 1991) is another useful source.
CHAPTER 2
The excerpt from Johan Huizinga, The Autumn of the Middle Ages, is translated by Rodney J. Payton and Ulrich Mammitzsch (Chicago: University of Chicago Press, 1996), 1-2.
1. Quote from the Annals of London from M. L. Parry, Climatic Change, Agriculture, and Settlement, 34. The literature on the North Atlantic Oscillation is enormous and hard to track. Here are some useful references with bibliographies: Edward R. Cook et al., "A Reconstruction of the North Atlantic Oscillation using tree-ring chronologies from North America and Europe," The Holocene 8(1) (1998): 9-17; Jurg Luterbacher et al., "Reconstruction of monthly NAO and EU indices back to A.D. 1675," Geophysical Research Letter, September 1, 1999: 2745-2748; M. J. Rodwell and others, "Oceanic forcing of the wintertime North Atlantic Oscillation and European climate," Nature 398: 320-323.
2. Cooling in the Arctic and the subsequent unpredictable conditions are well covered by Hubert Lamb
, Climate, History and the Modern World. The best source on the famine of 1316 is William Chester Jordan's The Great Famine (Princeton: Princeton University Press, 1996), which offers a comprehensive analysis and an im pressive bibliography. I have relied on this important work extensively in this chapter. Barbara W. Tuchman's A Distant Mirror: The Calamitous 14th Century (New York: Alfred A. Knopf, 1978) is a sweeping account of the century, which I also drew on here.The quotes in this paragraph are as follows:"E Floribus chronicum, etc., auctore Bernardo Guidonia," Martin Bouquet, et al., eds., Recuil des Historians des Gaules et de la France, 24 vols. (Paris, 1738-1904). 21:725."Excerpta e memoriali historiarum Johannis a sancto Victore," Bouquet et al., eds., Recuil des Historians, 21, 661."Extraits de la chronique attribuee a jean Desnouelles," Bouquet et al., eds., Recuil des Historians, 21, 197. I am deeply grateful to Professor William Jordan of Princeton University for kindly researching and translating these quotes for me.
3. Isaiah 5:25.
4. Henry S. Lucas, "The Great European Famine of 1315, 1316, and 1317," Speculum 5(4) (1930): 357.
5. Salzburg chronicler quoted from Jordan, The Great Famine, 18. 6. Ibid., 24.
7. Quotes from J. Z. Titow, "Evidence of weather in the account rolls of the Bishopric of Winchester," Economic History Review 12 (1960): 368.
8. The Neustadt vineyard research was the work of nineteenth-century German antiquarian Friedrich Dochnal. Quoted and discussed by Jordan, The Great Famine, 34-35.
