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 argued that the rapid warming of recent decades has in fact been driven mainly by non-CO, gases such as chlorofluorocarbons. Fossil fuel burning C02 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-CO, gases has declined over the past decade and could be reduced even further. This, combined with a slowing of black carbon and C0, 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 changebut 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 geenhouse 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 geat-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." 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.
