Climate Change, Ancient and Modern

I’ve just finished two fascinating and disturbing books. The first is Cyprian Broodbank’s monumental The Making of the Middle Sea, and the second is The Sixth Extinction, by Elizabeth Kolbert.

The first of these is a longue durée history of the Mediterranean Sea, beginning with its geological formation and tracing the rise of wildlife, Neanderthals, and current humans. The primary argument of the book—although not the most valuable part, which is just the sheer amount of information collected in one place—is that the Mediterranean as we know it today, the sea that links rather than divides, the ‘Middle Sea,’ is really only a creation of the last 5-6,000 years, particularly because the climate during these 5-6,000 years allowed the Mediterranean to develop the way that it did.

Because of the time scale, much of the book is concerned with changing climates and the ways that these affect human communities. One example among many would be the so-called “6200 Event,” in which a warming climate led to the massive breakoff of the last North American glaciers. This cooled the Earth for about 200 years (with temperature drops in the 6° C range) and devastated both hunter-gatherer and nascent agricultural communities around the basin. The agriculturalists, despite generally worse health and living standards, could multiply much more quickly and in the next half millennium replaced hunter-gatherers and began the “Neolithic Revolution.” We’ve never gone back to Eden

The Sixth Extinction is a popular book about the current mass extinction event—the sixth in the Earth’s history—that will probably wipe out something on an order of half of the Earth’s species over the next hundred years. Most North American bats are already dead, as are South American amphibians, and by 2100 ocean acidification will mean that there are no more coral reefs. Humans, of course, directly or indirectly cause all of these extinctions, whether by our carbon emissions that change the atmosphere or our global jaunts that bring new predators to areas where no defenses have been evolved against them. It’s not a happy book.

Now, the combination of these two books has driven home two things. First, climate change happens all the time, and it usually has nothing to do with humans. Second, the fact that it’s happening this time definitely does have to do with humans. Third, even when climate change doesn’t happen because of humans, it can be incredibly devastating to human communities and absolutely destroy civilizations. Don’t just ask the hunter-gatherers—ask any of the manifold groups of people obliviously living their lives along the Mediterranean whether they thought that their crops were going to fail, the Sahara could become an inhospitable desert, or the entire area they were living in would be sunk under the sea when the glaciers melted. 

This seems to be the major point that those who both deny (and often those who accept) anthropogenic climate change miss: this isn’t new, but it doesn’t matter. The world we live in is radically different from that of a century, millennium, or aeon ago. It will never stop changing, either, and we can’t control the change. But we can try to slow down the change that we are causing, because the speed at which we are changing the climate is dramatic. It’s dramatic, but not unprecedented—and what the precedents tell us are that rapid shifts in climate are really really bad for beings evolved to deal with a certain climate—and humans, or rather the entire structure of modern human life, with its interconnectivity and urban concentration, has evolved to succeed in one type of climate. And when the sea levels rise…well, I always had mixed feelings about New York.

Finally, it’s occurred to me that to really think about this stuff requires three time scales.  The first is generational time—my life, my kids’ lives, the lives of everyone I or they will ever know. The second is species scale—basically the future of humanity, or most of Broodbank’s book. The third is global geological scale, the scale that encompasses all six of the great extinctions in human history. I care about these scales in different, and sometimes not entirely coherent, ways. My next post will be teasing out those three different scales and how to live with changes that change on all three.



© Henry Gruber 2013