82 of 85 people found the following review helpful:
5.0 out of 5 stars
Fascinating account of ice ages and how they were discovered, June 23, 2005
This review is from: Frozen Earth: The Once and Future Story of Ice Ages (Hardcover)
This is an absolutely fascinating account of the various ice ages that have periodically taken over the earth. From the ancient "Snowball Earth" (sometimes called "Slushball Earth," 550 to 850 million years ago) in which the entire planet was more or less frozen from pole to pole, to the "Younger Dryas," a cold spell beginning 12,800 years ago and lasting for about 1,200 years, to "Little Ice Age" in Europe (700 to 150 years ago) to the "year without a summer," in 1816, UCSD Professor of Earth Sciences Doug MacDougall chronicles the ebb and flow of glacial advance and retreat in a most interesting and informative manner.
Much of this is a historical account of how scientists discovered the past ice ages through geology and the study of cores taken from the Antarctic, the Arctic, from the sea floor, and from still standing glacial ice packs. MacDougall explains how these cores are read to reveal climate changes in the past based on evidence from isotopes, pollen, and bubbles of trapped atmospheric gases. It is really amazing how much information can come from such minute bits of evidence.
In the early chapters MacDougall recalls the first scientists who became aware of the earth's climate in previous ages--Louis Agassiz, James Croll, Milutin Milankovitch and others. MacDougall recalls their efforts to get their ideas accepted by the geological establishment. It is fascinating to see how gradually it was realized that great rocks had arrived at various places, having been carried there by ancient glaciers. A particularly interesting story is how the Channeled Scablands of the Columbia Plateau in Washington were created when the glacial Lake Missoula sudden broke through the melting ice and drove an immense wall of water clear to the Pacific Ocean.
Part of his concentration is on the glacial and interglacial periods that have characterized the environment during the rise of the genus homo and especially the last 150,000 years or so during which homo sapiens have evolved. Chapter Ten, "Ice Ages, Climate, and Evolution" is devoted to how the advance and retreat of the ice affected the evolution of hominids and other animals and plants.
For those of us who might be worried about global warning it is perhaps refreshing to be warned that we are still living in an ice age. MacDougall writes, "We are in a warm period, one of the many interglacial intervals that have occurred throughout the Pleistocene Ice Age [now three million years old]." (p. 233)
Near the end of the book MacDougall looks at today's climate and takes into account the warming due to human activities, in particular the burning of fossil fuels. But he is not alarmed. He notes that the atmosphere on the planet Venus (surface temperature 485 degrees Centigrade, more than hot enough to melt lead) is almost all CO2 while that on earth is less than four-tenths of one percent CO2. No runaway greenhouse effect seems likely here any time soon. MacDougall explains the carbon dioxide cycle on earth and assures us that most CO2 is locked up in limestone. (p. 238)
While he seems unconcerned about global warming (taking the very long view) he does remark that "It is difficult to comprehend how further additions [of CO2] to the atmosphere at current rates could fail to raise global temperatures and possibly influence the course of the [current] Pleistocene Ice Age." (p. 241) Still he ends the book with this (possibly understated) possibility: "...mankind may inadvertently bring the Pleistocene Ice Age to a premature close, ushering in another long period of ice-free existence for our planet."
Which brings me to the question, if the earth does become more or less permanently as hot and muggy as a Jurassic swamp, what will it mean for human beings? There will be less land available since the melting of the glaciers would raise sea level some 60 meters, drowning New York and London, not to mention much of Florida and a host of South Pacific islands, Bangladesh, and other low-lying lands. Will we live most of our lives indoors in air-conditioned buildings? Will the verdant plants and fantastic diversity of creatures characteristic of tropical jungles be all around us? Will dragon flies be as big as birds?
On the other hand, suppose, as MacDougall intimates, that the forces affecting the earth's climate dwarf our puny doings. In that case the present interglacial will come to a close and the immediate future will be cold as the ice once again advances from the poles. As MacDougall points out, the air will be dryer with all that water locked up in ice, and great parts of the planet will be desert and the winds will blow the sand around the globe (as happened before during such periods as evidenced by the core samplings). I am reminded of the poet Robert Frost's dilemma, "Fire or Ice?" Probably our lives will not end in such extremes, but our way of life may change dramatically, and many will endure great hardships.
On the third hand, is it possible, maybe even probable, that we human beings will be able to affect the climate in such a way as to stave off the extremes? One of the cold-amplifying effects of great sheets of ice over the earth is to reflect sunlight and further cool the planet. Might not humans spread dark matter over the ice, melting it? Or in the case of too much CO2 or other greenhouse gases in the atmosphere, might humans somehow find a way to sink such gases and cool things down?
This is a distinguished work, very well written, beautifully edited, full of fascinating information about how cold the earth has been in the past (and how cold it might become again) and why.
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22 of 22 people found the following review helpful:
5.0 out of 5 stars
A Great Summer Book, July 29, 2005
This review is from: Frozen Earth: The Once and Future Story of Ice Ages (Hardcover)
Frozen Earth by Doug Macdougall is a fascinating book and it makes a great summer read as the heat beat downs and one tries to remember that we are in an ice age, albeit an interglacial period. The history of the discovery is told for all its glory and each chapter highlights a different personality related to the realization that the world has been through, and will continue to go through, a series of ice ages. The science is explained very neatly and the story is driven by the series of discoveries, beginning with Louis Agassiz to the very latest scientific discoveries, including alternate theories. The author also brings the story forward. All in all, a fascinating glimpse into our world, past, present, and future. Ice is a nice thing to think about on a hot summer day and this is just the book to get one truly thinking.
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16 of 17 people found the following review helpful:
5.0 out of 5 stars
Some perspective on the global climate, April 2, 2006
This review is from: Frozen Earth: The Once and Future Story of Ice Ages (Hardcover)
Doug Macdougall's "Frozen Earth" is clear, easy-to-read popular science for those interested in changes in global climate but without the scientific background to understand the often emotionally-charged discussion in the public media.
Macdougall's sub-title. "The Once and Future Story of Ice Ages", emphasizes the longer perspective he takes on how and why climate changes. He begins with the fact that we are likely living in an interglacial period of what has been a series of ice ages recurring at more or less regular intervals of several thousand years.
Macdougall gives his story a human aspect by describing how, over the last 300 years, a succession of scientists struggled to make sense of the physical evidence around them indicating that glaciers had once covered much more area than they do at present. The struggle leads to a still growing understanding of ice ages; the details of the story underline just how complex the workings of Planet Earth really are and how incomplete our understanding of these processes still is.
Macdougall loops back later in the book to relate how the ice ages interacted with human evolution; specifically, how the stress of environmental change forced both adaptation by early humans and selection of those best able to survive the changes. Macdougall's discussion of the "Little Ice Age" during the period 1600-1800 nicely links climate change to a human era we can still relate to.
Macdougall is properly cautious in weaving in the possible effects of mankind on climate change and global warming. The burning of carbon-based fuels clearly has some effect on climate, but Macdougall points out that this is only one of many factors that influence climate. At the same time, he makes clear that timing affects the impact of different factors, and lays out the possibility that the human impact may be altering the natural "schedule" of glacial and interglacial periods on earth.
This book is highly recommended to those readers interested in a longer perspective on climate change.
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