This position is ultimately quite puzzling. It's just not plausible to
assume that if sometime in Earth's history it was as warm as it is today,
we can relax. For hundreds of thousands of years, Earth's average tem-
peratures have varied widely, far more than most of us learned in science
classes. Until recently, in fact, the history of Earth's climate had barely reg-
istered in the popular mind. A good look at charts of temperatures over
the past 70,000 years or so—not to mention the last 600,000 years—will
certainly get one's atention: the lines on those charts bounce around
far more than one might initially have thought, slowing down into rela-
tive stability only in the very recent past, in the 10,000 years or so since
the most recent Ice Age—the period geologists call the Holocene. 174
Civilization as we know it arose on a planet prety much with its current
characteristics. In this rather brief, exceptional period, the Earth's climate
has created conditions that are ideal for certain kinds of human activities
to flourish. “Nature” for us is highly specific, very recent, and quite vulner-
able. Even for the first several thousand years after the Ice Age, we lived in
mobile hunter-gatherer communities and could adapt to new conditions
by changing our habitat. But with the rise and spread of the great seden-
tary, built civilizations, we are now rooted in specific places, much less
flexible, and deeply reliant on the endurance of our familiar landscapes.
The return of an Ice Age or the coming of a fully tropical planet, both
with ample precedent in Earth's history, would be an immense danger to
our way of life. Nothing we are used to, and no aspect of contemporary
civilization, would be the same if Earth entered one of these scenarios.
Rather than allowing us to dismiss the danger of climate change, then,
this version of “skepticism” only makes clearer how fragile civilization is,
how recent and potentially temporary.
If we are merely caught in yet another climatic shift, we must still
imagine how to cope. For the most part, those who claim that climate
change is not caused by human activities fight against efforts to do any-
thing substantial about our situation. Such a position is indeed consistent
with their sense that human action is not the cause of recent warming.
But if that warming is taking place and we can do nothing about it, then
how should we face the coming decades?
Anybody who actually believes that the current warming is entirely
natural should pause and think about the consequences of that claim. If it