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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.
9/2/2
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