May 2008
Intermediate to advanced
240 pages
5h 5m
English
Over the eons, Earth has been much colder and much warmer than it is now, without human help or hindrance. Over the past 12,000 years, the planet has generally been warming, removing such natural features as the glaciers that covered the upper Midwest of what is now the United States. It seems to be a truth that the process is continuing, probably hastened by carbon dioxide emitted by the furnaces and machines of man.
How much warming is from increased carbon dioxide, rather than other causes, and how much of the carbon-dioxide increase is from nonhuman sources, such as volcanoes? How erratic has the warming process been? Such physical questions have ...
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