I was aware of the little ice age prior to reading this book. But I didn't have a vivid image of what it was like. Fagan paints an intense picture of the famines, storms and unusual weather of the period through interesting anecdotes, triva and stories that in the hands of a lesser writer would appear disjointed. Fagan marshals this incredible range of detail to convey his thesis in a powerful way.

Fagan's thesis is that climate change matters -- it effects history in important ways that we cannot afford to overlook. He is not a determinist however, and never argues that weather causes history. Rather, he maintains that sudden and radical climate shifts create a background of social unrest over which history unfolds.

His climate data are from a variety of sources, the most rigourous of which are ice core samples and tree ring data. However, he also draws on diaries, newspapers, and the dates of grape harvests and uses information from archeological finds to add bits of weather information to the story. From this, he complies an overview of the climate between 1300 and 1850, and persuasively argues that that the weather during that period was, cooler, stormier and less predictable than the periods bracketing it. Fagan reviews data suggesting that the cooling may be related to sun spot cycles, volcanic erruptions and changes in the ocean currents, although the jury is still out the exact mechanisms at work.

This cooler weather created a variety of agricultural crises (some compounded by government incompetence) that generated social unrest among the peasant classes -- and this unrest played out on the historical stage in various ways. His most persuasive arguements are about the famines and crop failures that preceeded the French Revolution, although the sections on Ireland and England are also well done.

The one limitation of the book is that it avoids discussion of wars. Fagan admits in the conclusion that this was intentional -- he wanted to focus on background factors and avoid implying any kind of causal mechanism between weather and grand historic events like wars. However, at many places in the text I felt as if he was about to discuss war, and then shied away from it. This made the book feel somewhat incomplete. However, overall I found this book to be accessible, well-written and fascinating.