In Europe, until about the end of the 13th century AD, the climate appears to have been consistently mild and warm. Harvests were good, and in Britain and Scandinavia, farmers were able to cultivate land at altitudes where they cannot today. However, by the early 1300s, things were about to change for the worse, and within a century or so, a Little Ice Age would be under way.
Before reading this book, I had only a vague notion of what the Little Ice Age was. I knew about the Frost Fairs that took place on the ice-covered surface of the Thames, and about 1816, the "Year Without a Summer", but not much more than that.
This is why I have enjoyed reading Brian Fagan's The Little Ice Age. It is a beautifully informative and detailed account of what happened to weather patterns from the 1300s onwards, and what the consequences were for civilisation. The author, who is a writer, lecturer and archaeologist, focusses mostly on Europe and the Northern Hemisphere; however, this is not to say that other parts of the world were not affected - there is evidence from Peru, Antarctica and the Pacific which supports the notion that radical climate shifts were taking place. But it is from Europe especially that we have a wealth of written documentation from those times.
So what was the Little Ice Age? It was a period in history that stretched very roughly from the early 14th century to the early or mid 19th, and it was when unpredictable climatic extremes (especially harsh winters and cool summers) were much more common than they have been since.
Fagan describes some fascinating and sobering episodes in history, from the monstrous hailstorms that crushed crops and killed livestock in Europe and floods that drowned thousands, to the ominous advance of glaciers in the Alps, that in one instance led to the Bishop of Geneva being called upon to enlist God's help in holding back the ice.
Regarding possible causes for these extremes, the author draws attention to the link between sunspots and climate, with his descriptions of the various Grand Minima which occurred during the Little Ice Age - times when there were few or no sunspots, and when there were unusually cold conditions. If you have watched the film Girl with a Pearl Earring, you will have noticed scenes of canals in Delft, Holland, which would have been icebound at times during the Maunder Minimum, a period of reduced sunspots and freezing northern winters between about 1645 and 1715. (Incidentally, as I write this, I note that this year - 2008 - there have been a great number of months virtually free of sunspots, unusual even in a time of solar minimum.)
The author mentions, by the way, a delightfully quirky example of scientific research, in the form of Hans Neuberger's study of the sky in paintings, which shows the rise and fall of cloudy conditions in the heavens over Europe from 1400 to 1967. This is particularly intriguing, in the light of recent speculation linking cloud cover with climate change.
Although Fagan is careful not to assert that well-known historical events were directly caused by the climate, it would definitely have been a factor in many cases. Would Napoleon's retreat from Moscow have been the same without the severe winter of 1812? Would Washington have made different decisions at Valley Forge if things had been more comfortable for his army in the freezing December of 1777? The possible ramifications are difficult to ignore.
The maritime activities of Europeans that led to the discovery of the New World centuries earlier were also influenced by the climate - even as the Norse colonies in Greenland became untenable due to the cold, the migrations of herring and cod in the Atlantic were drawing English and Basque fishing boats ever further afield, and helped to fuel rumours of a vast new landmass to the west.
What conclusions have I drawn from this book? Firstly, that warm is generally better than cold (outside the tropics, at least.) Warmth means an extended growing season and mild winters. Cold means failed harvests, more winter deaths and glaciers encroaching on human settlements.
Secondly, that the climate is a complex and barely-understood thing. Ocean currents, winds, precipitation, cloud cover, changes to flora and fauna - all these cannot really be summed up by a single set of measurements. It was never the case that there were uniformly low global temperatures during the Little Ice Age, just as it was not the case that there were uniformly high global temperatures during the 20th century (this begs the question of whether there can truly be a global temperature, anyway.)
Thirdly, being a subsistence farmer is not generally a good idea. In the good years you will get by, and you will have enough to survive one failed harvest, maybe two. But if there are more than two bad years in a row, you will be in trouble. It was a series of poor wheat harvests in France that contributed to the unrest which fuelled the French Revolution. On the other hand, increased knowledge and innovation will help you - it was an agricultural revolution in the Netherlands and England which led farmers to diversify and practise crop rotation, lowering the risk of famine.
I highly recommend this book. Although the author does stand by the hypothesis that man-made carbon dioxide produced by industrialisation (and, he states, also by agriculture and land clearance) is a major cause of global warming - something of which I am not convinced - and that this is potentially a bad thing, he also presents enough historical evidence in The Little Ice Age to support other conclusions - that the sun's magnetic processes (as indicated by sunspot activity) may well have profound and far-reaching effects on the climate and that far from being a period of bucolic peace and plenty, the centuries before the mid-1800s featured a long-running display of climatic chaos that puts our current era into stark perspective.
If I had to choose between the mild warming of the late 20th century and the unpredictable frosts and storms of the Maunder Minimum, I would prefer the warming any day.