Originally written 9/2/2002
When I looked down into the Grand Canyon for the first time, I paused only for a moment at its immensity and moved right onto a more self-centered thought, “How tiny human history is in all of this, and even further, how much less significant my own life must be by extension.” It is clear that human beings will not outlast Nature.
An article in the January 7, 2002 New Yorker magazine, Ice Memory by Elizabeth Kolbert suggests that Nature will win out in even the shorter run than my earlier musings. Greenland is about the size of France and 80% covered by ice. The ice sheet or glacier is over ten thousand feet thick. “A hundred and thirty-eight feet down, there is snow dating from the American Civil War; some twenty-five hundred feet down, snow from the days of Plato, and, five thousand three hundred and fifty feet down, from the time when prehistoric painters were decorating the caves at Lascaux. At the very bottom, there is snow that fell on Greenland before the last ice age, which began more than a hundred thousand years ago.” Starting in 1959 and continuing sporadically to this day, teams from various countries have drilled down through this ice and extracted cores on four or more occasions. At first no one was very interested in the cores, but a clever Danish scientist developed a technique that allowed for an accurate reading of the atmospheric temperature at the time each layer was deposited. This involves the ratio of two oxygen isotopes in rain water that is temperature dependent.
So, what do these ice cores reveal about the earth’s climate? “Its hard to look much further back in the record, however, without feeling a little queasy. About twenty thousand years ago, the Earth was still in the grip of the last ice age. During this period, called the Wisconsin by American scientists, ice sheets covered nearly a third of the world’s landmass, reaching as far south a New York City. The transition out of the Wisconsin is preserved in great detail in the Greenland ice. What the record shows is that it was a period of intense instability. The temperature did not rise slowly , or even steadily; instead, the climate flipped several times from temperate conditions back into those of an ice age, and then back again. Around fifteen thousand years ago, Greenland abruptly warmed by sixteen degrees in fifty years or less. In one particularly traumatic episode some twelve thousand years ago, the mean temperature in Greenland shot up by fifteen degrees in a single decade.”
So, over the last hundred thousand years of climate history captured in the ice there have been dozens of episodes of wild swings in temperature. But, taking a longer view, the earth has oscillated through warm periods of ten thousand years followed by ninety thousand years of cold during the last half million years. The warm period we now live in is now ten thousand years old; a cold period should follow. Although us humans are persisting in all sorts of un-neighborly activities, in the end, we may not have enough time to do ourselves in before Nature catches us.