The Two-Mile Time Machine: Ice Cores, Abrupt Climate Change, and Our Future

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Princeton University Press, 2002 - Science - 240 pages

Richard Alley, one of the world's leading climate researchers, tells the fascinating history of global climate changes as revealed by reading the annual rings of ice from cores drilled in Greenland. In the 1990s he and his colleagues made headlines with the discovery that the last ice age came to an abrupt end over a period of only three years. Here Alley offers the first popular account of the wildly fluctuating climate that characterized most of prehistory--long deep freezes alternating briefly with mild conditions--and explains that we humans have experienced an unusually temperate climate. But, he warns, our comfortable environment could come to an end in a matter of years.

The Two-Mile Time Machine begins with the story behind the extensive research in Greenland in the early 1990s, when scientists were beginning to discover ancient ice as an archive of critical information about the climate. Drilling down two miles into the ice, they found atmospheric chemicals and dust that enabled them to construct a record of such phenomena as wind patterns and precipitation over the past 110,000 years. The record suggests that "switches" as well as "dials" control the earth's climate, affecting, for example, hot ocean currents that today enable roses to grow in Europe farther north than polar bears grow in Canada. Throughout most of history, these currents switched on and off repeatedly (due partly to collapsing ice sheets), throwing much of the world from hot to icy and back again in as little as a few years.

Alley explains the discovery process in terms the general reader can understand, while laying out the issues that require further study: What are the mechanisms that turn these dials and flip these switches? Is the earth due for another drastic change, one that will reconfigure coastlines or send certain regions into severe drought? Will global warming combine with natural variations in Earth's orbit to flip the North Atlantic switch again? Predicting the long-term climate is one of the greatest challenges facing scientists in the twenty-first century, and Alley tells us what we need to know in order to understand and perhaps overcome climate changes in the future.

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Richard Alley’s The Two Mile Time Machine: Ice Cores, Abrupt Change, and Our Future provides a good, though slightly dated, explanation
of the science of ice core sampling, as a means for studying the history of Earth’s climate. Alley focuses on work conducted in Greenland prior to 2000. The book combines some surprisingly informal background sections with some rather technical passages about isotopic ratios and climatic cycles. Overall, it is a book that highlights the scientific tendency to dive right into the details of one area of inquiry, while skimming over many others that actually relate closely - especially if you are trying to use the science as the basis for sound decision-making.
This book does not really warrant inclusion in the first tier of books to read on climate change, but it certainly provides some useful background for those trying to develop a comprehensive understanding of the area. Arguably, the best contribution it makes is explaining the causes and characteristics of very long climatic cycles: those stretching over millennia or millions of years, with causes including orbital variation, continental drift, and cryosphere dynamics.
Given the amount of new data and analysis that has been undertaken since this book was published, a new edition may well be warranted. In particular, the very tenuous conclusions of Alley’s concluding chapters should either be revised, or defended in the fact of the new data.

About the author (2002)

Richard B. Alley, Professor of Geosciences at Pennsylvania State University, where he teaches and conducts research on climate change and glacier behavior. A Fellow of the American Geophysical Union, he recently chaired the National Research Council committee that produced the report "Abrupt Climate Changes: Inevitable Surprises." He has won both teaching and research awards for his work, which has included five expeditions to Greenland and three to Antarctica. He has published numerous articles in leading journals such as Science, Nature, and Scientific American.

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