Global Change and Our Common Future Papers from a Forum (1989) / Chapter Skim
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4. The Earth System
4. The Earth System
Pages 31-33
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From page 31... ...
Its liquid core and mantle are heated by radioactive elements that still remain from its origins some 4.5 billion years ago. This heat induces ongoing crustal and mantle movement described under the general term "plate tectonics." Within this system there are many subsystems of change at present acting at different rates, some rhythmic and others episodic.
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From page 32... ...
We are now able to chart past and current environmental changes, and techniques recently developed enable us to view the land, oceans, and atmosphere from space, and to measure secular changes in climate, cloud and ice cover, soil moisture, and marine and land big-productivity. Ice cores have furnished an accurate record as far back as 160,000 years of global temperature, levels of atmospheric carbon dioxide, and variations year by year in wind-borne sediments, including volcanic events.
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From page 33... ...
I I believe, therefore, that it is perfectly proper, as a scientist, to appeal for an inductive approach in looking at our present condition on earth, to draw empirical conclusions, including constructing some worst-case scenarios, and to attempt to assign probabilities to them. I began these remarks by focusing on the earth system, and I find that ~ - suggest that we do not know enough We are forcing our will upon it, using steadily depleting resources and increasing waste discharge, while at same time claiming that we must aim for sustainability.
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