American Scientist

The Little Ice Age: How Climate Made History, 1300–1850. Brian Fagan. xxii + 246 pp. Basic Books, 2000. $26.

Compared with the Ice Age that preceded the melting of the great continental ice sheets about 10,000 years ago, the Little Ice Age was small stuff. Lasting from the early Renaissance to the middle of the 19th century, it was characterized by a cooling of less than one degree Celsius.

That average temperature change seems small—what's a degree or so? We have trouble judging how much difference even several degrees of global warming will make in our lives. By focusing on temperature per se, we conveniently ignore the more important aspects of climate change: floods, droughts, high winds, dust storms and unseasonable weather that ruins harvests. But unsettling extremes of that sort?not the thermometer readings?are what caused people to starve during the Little Ice Age.

Studying the era, as Brian Fagan points out in The Little Ice Age, "reminds us that climate change is inevitable, unpredictable, and sometimes vicious." The Little Ice Age had a human scale—we can almost imagine it by extrapolating from bad storms and droughts of the 20th century. Picturing it may help us begin to imagine more abrupt jumps of the kind that have recurred every few thousand years, involving tenfold greater temperature excursions and far more widespread disruption of ecosystems.

Fagan is an archaeologist with a deep knowledge of European history and climate. He notes that most historians have downplayed the importance of climate in shaping past events, a caution that was appropriate in an earlier era. But now we have better data:

For the first time, we place a detailed graph of changing climate alongside the momentous historical events of the Little Ice Age, not as a remote backdrop but as a critical, and long neglected, factor in a complex equation of harvests, subsistence crises, and economic, political and social changes. We can see how cycles of cold or of excessive rainfall rippled across Europe, affecting monarch, noble, and commoner in different ways, changing the course of wars and the prosperity of fisheries, and fostering agricultural innovation. Climate change was a subtle catalyst, not a cause, of profound change in a European world where everyone lived at the complete mercy of a subsistence farming economy.

The present book, which is written for a general audience, is a considerable expansion of a chapter in Fagan's Floods, Famines, and Emperors: El Ni?o and the Fate of Civilizations (Basic Books, 1999). The Little Ice Age has four parts: Brief sections on the Medieval Warm Period (900?1200 a.d.) and the Modern Warm Period frame the two longer sections on the Little Ice Age itself. Given the relative wealth of historical climate data from European sources, this is mostly a story about Europe and Greenland, with only occasional glimpses of glacial advances in New Zealand. Fagan does not attempt to tackle such puzzles as why the Medieval Warm Period was a bad time for East Africa and the Little Ice Age was a much more prosperous time there (despite three major droughts lasting 30, 65 and 80 years).

Fagan tries to show how climate influences overlay, and stimulated, the modernization of European agriculture. His discussions of the socioeconomic aspects of climate change offer readers additional insights into such events as the French Revolution.

We can think about one cause and its most obvious consequences, but factoring in several simultaneous causes usually requires much effort. Politicians and members of the press who read only "executive summaries" of climate-change reports routinely further oversimplify what they read and then pass on to the public even less of whatever wisdom was originally there. And since nothing expensive gets done unless politicians believe they have the people behind them, the world's largest democracies may fail to act in time to slow global warming. Books like Fagan's are important in framing the issue and suggesting what may lie ahead for us by providing a gut-level notion of what catastrophic climate change is like.—William H. Calvin, Psychiatry and Behavioral Sciences, University of Washington, Seattle