A Choice of Catastrophes_The Disasters That Threaten Our World by Isaac Asimov

Author:Isaac Asimov [Asimov, Isaac]
Language: eng
Format: epub
Tags: science, non-fiction
ISBN: 9780449900482
Amazon: 0449900487
Publisher: Ballantine Books
Published: 1981-09-12T00:00:00+00:00

TRIGGERING THE GLACIERS

The ice ages of the last million years have obviously not brought an end of life on the planet. They didn’t even put an end to human life. Homo sapiens and its hominid ancestors lived all through the ice ages of the last million years without any noticeable interruption of rapid evolution and development.

Nevertheless, it is fair to wonder whether another period of glaciation is ahead of us or whether it is all part of the past. Even if an ice age does not mean an end to life or even to humanity, and is not catastrophic in that sense, the thought of almost all of Canada and of the northern quarter of the United States under a mile-deep glacier (to say nothing of portions of Europe and Asia similarly iced) might seem quite bad enough.

To decide whether the glaciers might return, it would help to learn first what causes such periods of glaciation. And before trying to do that, we must understand that it doesn’t take much to start the glaciers moving; we don’t have to postulate large and impossible changes.

Right now, snow falls over much of northern America and Eurasia every winter and leaves all that region covered with frozen water almost as though the Ice Age had returned. The snow cover, however, is only a few cenitimetres to a couple of metres thick, and in the course of the summer it all melts. There is, in general, a balance and on the average as much snow melts in the summer as falls in the winter. There is no overall change.

But suppose that something happens which cools the summers just a bit, perhaps only two or three degrees. This would not be enough to notice, and of course it would not be a steady change. There would continue to be warmer summers and cooler summers in some random distribution, but the warmer summers would occur less frequently so that, on the average, the snow that fell in the winter would not quite all melt in the summer. There would be a net increase in snow cover from year to year. This would be a very slow increase and it would be noticeable in the northern polar and subpolar regions and in the higher mountainous regions. The accumulating snow would turn to ice and the glaciers that exist in the polar regions and at higher elevations even in southerly latitudes would extend farther in the winter and retreat less in the summer. They would grow from year to year.

The change would feed on itself. Ice reflects light more efficiently than bare rock or soil does. In fact, ice reflects some 90 per cent of the light that falls on it, while bare soil reflects less than 10 per cent. This means that as the ice cover expands, more sunlight is reflected and less is absorbed. The average temperature of the Earth would drop a little farther, summers would grow a trifle cooler still, and the ice cover would expand still more rapidly.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.