Brian Fagan’s most recent book, The Great Warming, is a historical narrative about what he calls the Medieval Warm Period. Between roughly 800 and 1200 A.D., the Earth experienced an increase in temperature on the average of 1 degree Celsius. This seemingly small change saw the expansion of Europe, the eastward development of Polynesia, and widespread droughts in places like Central America, where the advanced Maya civilization utterly collapsed.

For history buffs, the book is thoroughly entertaining. It provides new answers to questions long pondered about some of history’s most famous episodes (such as what forced the Mongols from the Eurasian steppe?) But the book’s value for green thinkers lies in the much-needed amendments Fagan offers to typical climate talk. 

Fagan’s book corrects two common errors found in much of our discussion of global warming. It shows that constructive consideration of the climate situation can (and should) be oriented to the past – not just the present and future. And, secondly, it brings attention to what Fagan calls the Silent Elephant in the Room: drought.

The current global warming dialogue often seems hyper-focused on the sheer wetness of a warmer Earth. And indeed, water is a cause for concern. Higher seas will overwhelm a number of heavily populated areas and many regions will suffer from higher rainfall and more severe storms.

But this focus on water is rather odd. When we think about things becoming warmer, we usually worry about them drying out. And it’s the dry, as much as the wet, that we should be worried about. Though the Earth will certainly see an increase in water coverage, many of the areas “lucky enough” to remain dry land will become something terrible: very, very dry land.

Fagan paints a vivid picture of just how terrible dry land can be. His narrative vividly illustrates the horrific suffering of individuals and societies decimated by drought. California’s Sierras, the Eurasian Steppe, Northern China and the Yucatan -- where the entire Maya civilization was destroyed by repeated and sustained droughts -- are just some of the illustrations Fagan provides. These historical portraits supply a needed supplement to the facts and figures (the stale computer modeling of weather patterns) that dominate much eco-thinking.

All said, Fagan’s book should remind environmentalists of the importance of a past that can teach difficult lessons about the precariousness of human existence and the realities of human suffering, without which we might never fully acknowledge the situation we face- - and the difficult demands we must meet.

Fagan makes the case impeccably: “History is always around us, threatening, offering encouragement, sometimes showing us precedents. The warm centuries of a thousand years ago remind us that we have never been masters of the nature world; at our best, we have accommodated ourselves to its fickle realities.”

But the author also shows us a fact of climate change that has largely evaded discussion, but which is surely worth consideration: that global warming is sure to produce winners as well as losers.

The Medieval Warm Period allowed the population of Western Europe to grow exponentially, thanks to plentiful crops and general good health. The extra population led to extra revenue, which allowed then ill-defined states to become more robust, leading ultimately to the strong states that drove European history from the 15th century to today. The abnormal warmth also allowed for geographic expansion, prompting Norsemen to colonize parts of Greenland and even North America.

In the end, however, we see that winning out thanks to climate (or anything else) leads, ironically, to environmental degradation -- often the very same degradation that brings on the next change in climate, which will likely be less kind to former winners, and which could very well prove their ruin.

As Europe grew, it suffered terrible deforestation, losing nearly half its forests to the growing need for farm land. Moreover, Europe’s general good fortune led to its world dominance in the centuries to come -- leading, in turn, to industrialization and, ultimately, to our current highly polluted situation: on the verge of another great warming.

And if the droughts of the Medieval Warm Period seem bad -- and thanks to the author’s narrative skill they do -- those of the future will be considerably worse.

In the endlessly thought-provoking final chapter, Fagan abandons history for a frightening discussion of where the world is headed -- not just in the long term, but in the near term as well.

Within 15 years, for example, nearly 2.3 billion people will live in areas desperately in need of water. And that scenario leaves unconsidered the likelihood that those places will be destabilized and severely overpopulated, having absorbed entire societies during the wild population shifts Fagan sees characterizing our dry (and flooded) future.

In all, it’s enough to frighten. And Fagan offers little comfort. He does, however, offer a recipe of sorts for overcoming … well, ourselves: 

“Drought and water are probably the overwhelmingly important issues for this and future centuries, times when we will have to become accustomed to making altruistic decisions that will benefit not necessarily ourselves but generations yet unborn. This requires political and social thinking of a kind that barely exists today, where instant gratification and the next election seem more important than acting with a view to the long-term future.”

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