A dossier on a 550-year European cold snap compiled from tree rings, ice cores, and the accounts of country clergymen and gentlemen scientists. Do we make the weather, or does it make us?

Because the Arctic ice pack receded during the preceding Medieval Warm Period, Fagan writes, the Vikings invaded Europe from England to Tuscany and even Constantinople. Because the Arctic ice pack receded the Atlantic cod moved north and provided a food source for regular trips to Greenland, which the Vikings then colonized. Because the Arctic ice pack receded the Basques were able to cross the Atlantic to find the rich fishing grounds off the Newfoundland Banks.

When the Arctic ice pack returned with the beginnings of the Little Ice Age in 1300, the trips ceased and the colonies died out or were absorbed by the Native population. Drought in the middle of the Little Ice Age caused Spanish settlers to move their colony from South Carolina to Florida, which as Fagan puts it “may help explain why most people in the southeastern United States speak English rather than Spanish.”

There is no study Fagan does not exploit in his exploration of his topic, including a delightful analysis by American meteorologist Hans Neuberger, who looked at 12,000 landscape paintings in museums in the US and Europe, painted between 1400-1967, to study the clouds in the skies of the paintings and to make some estimate of current weather conditions thereby.

His statistical analysis revealed a slow increase in cloudiness between the beginning of the fifteenth and the mid-sixteenth centuries, followed by a sudden jump in cloud cover.

Curious scientists have the most fun.

In 1800, at the end of the Little Ice Age and the beginning of the industrial revolution, the population of the planet was  one billion. Today it’s 7.4 billion and we’re all burning fossil fuels to heat our homes, power our generators, drive to work and fly somewhere on vacation. It’s impossible for me to look at those figures and think that we are having no effect on climate, but as Fagan’s book reminds us, we are only exacerbating a global weather shift that has happened before and continues now. Fagan writes

Slow cyclical changes in the eccentricity of the earth’s orbit and in the tilt and orientation of its spin axis have constantly changed patterns of evaporation and rainfall and the intensity of the passing seasons over the past 730,000 years. As a result, the world has shifted constantly between extreme cold and short warmer periods.

So maybe we should stop fighting over whether it’s happening and start working on how we can adapt to it.